Community-based evaluation of immigrant tuberculosis screening using interferon γ release assays and tuberculin skin testing: observational study and economic analysis

Cost-effectiveness of active tuberculosis screening among high-risk populations in low tuberculosis incidence countries: a systematic review, 2008 to 2023

BackgroundIn countries with a low TB incidence (≤ 10 cases/100,000 population), active pulmonary tuberculosis (PTB) mostly affects vulnerable populations with limited access to healthcare. Thus, passive case-finding systems may not be successful in detecting and treating cases and preventing further transmission. Active and cost-effective search strategies can overcome this problem.AimWe aimed to review the evidence on the cost-effectiveness (C-E) of active PTB screening programmes among high-risk populations in low TB incidence countries.MethodsWe performed a systematic literature search covering 2008-2023 on PubMed, Embase, Center for Reviews and Dissemination, including Database of Abstracts of Reviews of Effects (DARE), National Health Services Economic Evaluation Database (NHS EED), Global Index Medicus and Cochrane Central Register of Controlled Trials (CENTRAL).ResultsWe retrieved 6,318 articles and included nine in this review. All included studies had an active case-finding approach and used chest X-ray, tuberculin skin test, interferon-gamma release assay and a symptoms questionnaire for screening. The results indicate that screening immigrants from countries with a TB incidence > 40 cases per 100,000 population and other vulnerable populations as individuals from isolated communities, people experiencing homelessness, those accessing drug treatment services and contacts, is cost-effective in low-incidence countries.ConclusionIn low-incidence countries, targeting high-risk groups is C-E. However, due to the data heterogenicity, we were unable to compare C-E. Harmonisation of the methods for C-E analysis is needed and would facilitate comparisons. To outline comprehensive screening and its subsequent C-E analysis, researchers should consider multiple factors influencing screening methods and outcomes.

Economic evaluation of novel Mycobacterium tuberculosis specific antigen-based skin tests for detection of TB infection: A modelling study

Evidence on the economic impact of novel skin tests for tuberculosis infection (TBST) is scarce and limited by study quality. We used estimates on the cost-effectiveness of the use of TBST compared to current tuberculosis infection (TBI) tests to assess whether TBST are affordable and feasible to implement under different country contexts. A Markov model parametrised to Brazil, South Africa and the UK was developed to compare the cost-effectiveness of three TBI testing strategies: (1) Diaskintest (DST), (2) TST test, and (3) IGRA QFT test. Univariate and probabilistic sensitivity analyses over unit costs and main parameters were performed. Our modelling results show that Diaskintest saves $5.60 and gains 0.024 QALYs per patient and $8.40, and 0.01 QALYs per patient in Brazil, compared to TST and IGRA respectively. In South Africa, Diaskintest is also cost-saving at $4.39, with 0.015 QALYs per patient gained, compared to TST, and $64.41, and 0.007 QALYs per patient, compared to IGRA. In the UK, Diaskintest saves $73.33, and gaines 0.0351 QALYs per patient, compared to TST. However, Diaskintest, compared to IGRA, showed an incremental cost of $521.45 (95% CI (500.94-545.07)) per QALY, below the willingness-to-pay threshold of $20.223 per QALY. Diaskintest potentially saves costs and results in greater health gains than the TST and IGRA tests in Brazil and South Africa. In the UK Diaskintest would gain health but also be more costly. Our results have potential external validity because TBST remained cost-effective despite extensive sensitivity analyses.

The Global Expansion of LTBI Screening and Treatment Programs: Exploring Gaps in the Supporting Economic Evidence

The global burden of latent TB infection (LTBI) and the progression of LTBI to active TB disease are important drivers of ongoing TB incidence. Addressing LTBI through screening and TB preventive treatment (TPT) is critical in order to end the TB epidemic by 2035. Given the limited resources available to health ministries around the world in the fight against TB, we must consider economic evidence for LTBI screening and treatment strategies to ensure that limited resources are used to achieve the biggest health impact. In this narrative review, we explore key economic evidence around LTBI screening and TPT strategies in different populations to summarize our current understanding and highlight gaps in existing knowledge. When considering economic evidence supporting LTBI screening or evaluating different testing approaches, a disproportionate number of economic studies have been conducted in high-income countries (HICs), despite the vast majority of TB burden being borne in low- and middle-income countries (LMICs). Recent years have seen a temporal shift, with increasing data from low- and middle-income countries (LMICs), particularly with regard to targeting high-risk groups for TB prevention. While LTBI screening and prevention programs can come with extensive costs, targeting LTBI screening among high-risk populations, such as people living with HIV (PLHIV), children, household contacts (HHC) and immigrants from high-TB-burden countries, has been shown to consistently improve the cost effectiveness of screening programs. Further, the cost effectiveness of different LTBI screening algorithms and diagnostic approaches varies widely across settings, leading to different national TB screening policies. Novel shortened regimens for TPT have also consistently been shown to be cost effective across a range of settings. These economic evaluations highlight key implementation considerations such as the critical nature of ensuring high rates of adherence and completion, despite the costs associated with adherence programs not being routinely assessed and included. Digital and other adherence support approaches are now being assessed for their utility and cost effectiveness in conjunction with novel shortened TPT regimens, but more economic evidence is needed to understand the potential cost savings, particularly in settings where directly observed preventive therapy (DOPT) is routinely conducted. Despite the growth of the economic evidence base for LTBI screening and TPT recently, there are still significant gaps in the economic evidence around the scale-up and implementation of expanded LTBI screening and treatment programs, particularly among traditionally hard-to-reach populations.

A cost-effectiveness evaluation of latent tuberculosis infection screening of a migrant population in Malaysia

To estimate the costs and benefits of screening for latent tuberculosis infection (LTBI) in a migrant population in Malaysia. An economic model was developed from a Malaysian healthcare perspective to compare QuantiFERON-TB Gold Plus (QuantiFERON) with the tuberculin skin test (TST). A decision tree was used to capture outcomes relating to LTBI screening followed by a Markov model that simulated the lifetime costs and benefits of the patient cohort. The Markov model did not capture the impact of secondary infections. The model included an R shiny interactive interface to allow adaptation to other scenarios and settings. QuantiFERON is both more effective and less costly than TST (dominant). Compared with QuantiFERON, the lifetime risk of developing active TB increases by approximately 40% for TST due to missed LTBI cases during screening (i.e. a higher number of false negative cases for TST). For a migrant population in Malaysia, QuantiFERON is cost-effective when compared with TST. Further research should consider targeted LTBI screening for migrants in Malaysia based on common risk factors.

Effectiveness of nationwide programmatic testing and treatment for latent tuberculosis infection in migrants in England: a retrospective, population-based cohort study

Background

In low-incidence countries, tuberculosis mainly affects migrants, mostly resulting from reactivation of latent tuberculosis infection (LTBI) acquired in high-incidence countries before migration. A nationwide primary care-based LTBI testing and treatment programme for migrants from high-incidence countries was therefore established in high tuberculosis incidence areas in England. We aimed to assess the effectiveness of this programme.

Methods

We did a retrospective, population-based cohort study of migrants who registered in primary care between Jan 1, 2011, and Dec 31, 2018, in 55 high-burden areas with programmatic LTBI testing and treatment. Eligible individuals were aged 16–35 years, born in a high-incidence country, and had entered England in the past 5 years. Individuals who tested interferon-γ release assay (IGRA)-negative were advised about symptoms of tuberculosis, whereas those who tested IGRA-positive were clinically assessed to rule out active tuberculosis and offered preventive therapy. The primary outcome was incident tuberculosis notified to the national Enhanced Tuberculosis Surveillance system.

Findings

Our cohort comprised 368 097 eligible individuals who had registered in primary care, of whom 37 268 (10·1%) were tested by the programme. 1446 incident cases of tuberculosis were identified: 166 cases in individuals who had IGRA testing (incidence 204 cases [95% CI 176–238] per 100 000 person-years) and 1280 in individuals without IGRA testing (82 cases [77–86] per 100 000 person-years). Overall, in our primary analysis including all diagnosed tuberculosis cases, a time-varying association was identified between LTBI testing and treatment and lower risk of incident tuberculosis (hazard ratio [HR] 0·76 [95% CI 0·63–0·91]) when compared with no testing. In stratified analysis by follow-up period, the intervention was associated with higher risk of tuberculosis diagnosis during the first 6 months of follow-up (9·93 [7·63–12·9) and a lower risk after 6 months (0·57 [0·41–0·79]). IGRA-positive individuals had higher risk of tuberculosis diagnosis than IGRA-negative individuals (31·9 [20·4–49·8]). Of 37 268 migrants who were tested, 6640 (17·8%) were IGRA-positive, of whom 1740 (26·2%) started preventive treatment. LTBI treatment lowered the risk of tuberculosis: of 135 incident cases in the IGRA-positive cohort, seven cases were diagnosed in the treated group (1·87 cases [95% CI 0·89–3·93] per 1000 person-years) and 128 cases were diagnosed in the untreated group (10·9 cases [9·16–12·9] per 1000 person-years; HR 0·14 [95% CI 0·06–0·32]).

Interpretation

A low proportion of eligible migrants were tested by the programme and a small proportion of those testing positive started treatment. Despite this, programmatic LTBI testing and treatment of individuals migrating to a low-incidence region is effective at diagnosing active tuberculosis earlier and lowers the long-term risk of progression to tuberculosis. Increasing programme participation and treatment rates for those testing positive could substantially impact national tuberculosis incidence.

Funding

National Institute for Health Research Health Protection Research Unit in Respiratory Infections.

Cost-effectiveness of testing for latent tuberculosis infection in people with HIV

OBJECTIVE

The aim of this study was to estimate the cost-effectiveness of screening strategies for predicting LTBI that progresses to active tuberculosis (TB) in people with HIV.

DESIGN

We developed a decision-analytical model that constituted a decision tree covering diagnosis of LTBI and a Markov model covering progression to active TB. The model represents the lifetime experience following testing for LTBI, and discounting costs, and benefits at 3.5% per annum in line with UK standards. We undertook probabilistic and one-way sensitivity analyses.

SETTING

UK National Health Service and Personal Social Service perspective in a primary care setting.

PARTICIPANTS

Hypothetical cohort of adults recently diagnosed with HIV.

INTERVENTIONS

Interferon-gamma release assays and tuberculin skin test.

MAIN OUTCOME MEASURE

Cost per quality-adjusted life year (QALY).

RESULTS

All strategies except T-SPOT.TB were cost-effective at identifying LTBI, with the QFT-GIT-negative followed by TST5mm strategy being the most costly and effective. Results indicated that there was little preference between strategies at a willingness-to-pay threshold of £20 000. At thresholds above £40 000 per QALY, there was a clear preference for the QFT-GIT-negative followed by TST5mm, with a probability of 0.41 of being cost-effective. Results showed that specificity for QFT-GIT and TST5mm were the main drivers of the economic model.

CONCLUSION

Screening for LTBI has important public health and clinical benefits. Most of the strategies are cost-effective. These results should be interpreted with caution because of the paucity of studies included in the meta-analysis of test accuracy studies. Additional high-quality primary studies are needed to have a definitive answer about, which strategy is the most effective.

Systematic review of latent tuberculosis infection research to inform programmatic management in Ireland

The World Health Organisation (WHO) End Tuberculosis (TB) Strategy and the WHO Framework Towards Tuberculosis Elimination in Low Incidence Countries state that latent tuberculosis infection (LTBI) screening and treatment in selected high-risk groups is a priority action to eliminate TB. The European Centre for Disease Prevention and Control (ECDC) advises that this should be done through high-quality programmatic management, which they describe as having six key components. The research aim was to systematically review the literature to identify what is known about the epidemiology of LTBI and the uptake and completion of LTBI screening and treatment in Ireland to inform the programmatic management of LTBI nationally. A systematic literature review was performed according to a review protocol and reported in adherence with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement. Twenty-eight studies were eligible for inclusion and described LTBI screening or treatment performed in one of five contexts, pre-biologic or other immunosuppression screening, people living with HIV, TB case contacts, other vulnerable populations, or healthcare workers. The risk of bias across studies with regard to prevalence of LTBI was generally high. One study reported a complete cascade of LTBI care from screening initiation to treatment completion. This systematic review has described what published research there is on the epidemiology and cascade of LTBI care in Ireland and identified knowledge gaps. A strategy for addressing these knowledge gaps has been proposed.

Cross-sectional study of prevalence and risk factors, and a cost-effectiveness evaluation of screening and preventive treatment strategies for latent tuberculosis among migrants in Singapore

OBJECTIVES

WHO recommends that low burden countries consider systematic screening and treatment of latent tuberculosis infection (LTBI) in migrants from high incidence countries. We aimed to determine LTBI prevalence and risk factors and evaluate cost-effectiveness of screening and treating LTBI in migrants to Singapore from a government payer perspective.

DESIGN

Cross-sectional study and cost-effectiveness analysis.

SETTING

Migrants in Singapore.

PARTICIPANTS

3618 migrants who were between 20 and 50 years old, have not worked in Singapore previously and stayed in Singapore for less than a year were recruited.

PRIMARY AND SECONDARY OUTCOME MEASURES

Costs, quality-adjusted life-years (QALYs), threshold length of stay, incremental cost-effectiveness ratios (ICERs), cost per active TB case averted.

RESULTS

Of 3584 migrants surveyed, 20.4% had positive interferon-gamma release assay (IGRA) results, with the highest positivity in Filipinos (33.2%). Higher LTBI prevalence was significantly associated with age, marital status and past TB exposure. The cost-effectiveness model projected an ICER of S$57 116 per QALY and S$12 422 per active TB case averted for screening and treating LTBI with 3 months once weekly isoniazid and rifapentine combination regimen treatment compared with no screening over a 50-year time horizon. ICER was most sensitive to the cohort's length of stay in Singapore, yearly disease progression rates from LTBI to active TB, followed by the cost of IGRA testing.

CONCLUSIONS

For LTBI screening and treatment of migrants to be cost-effective, migrants from high burden countries would have to stay in Singapore for ~50 years. Risk-stratified approaches based on projected length of stay and country of origin and/or age group can be considered.

Management and control of tuberculosis control in socially complex groups: a research programme including three RCTs

Background

Socially complex groups, including people experiencing homelessness, prisoners and drug users, have very high levels of tuberculosis, often complicated by late diagnosis and difficulty in adhering to treatment.

Objective

To assess a series of interventions to improve tuberculosis control in socially complex groups.

Design

A series of observational surveys, evaluations and trials of interventions.

Setting

The pan-London Find&Treat service, which supports tuberculosis screening and case management in socially complex groups across London.

Participants

Socially complex groups with tuberculosis or at risk of tuberculosis, including people experiencing homelessness, prisoners, drug users and those at high risk of poor adherence to tuberculosis treatment.

Interventions and main outcome measures

We screened 491 people in homeless hostels and 511 people in prison for latent tuberculosis infection, human immunodeficiency virus, hepatitis B and hepatitis C. We evaluated an NHS-led prison radiographic screening programme. We conducted a cluster randomised controlled trial (2348 eligible people experiencing homelessness in 46 hostels) of the effectiveness of peer educators (22 hostels) compared with NHS staff (24 hostels) at encouraging the uptake of mobile radiographic screening. We initiated a trial of the use of point-of-care polymerase chain reaction diagnostics to rapidly confirm tuberculosis alongside mobile radiographic screening. We undertook a randomised controlled trial to improve treatment adherence, comparing face-to-face, directly observed treatment with video-observed treatment using a smartphone application. The primary outcome was completion of ≥ 80% of scheduled treatment observations over the first 2 months following enrolment. We assessed the cost-effectiveness of latent tuberculosis screening alongside radiographic screening of people experiencing homelessness. The costs of video-observed treatment and directly observed treatment were compared.

Results

In the homeless hostels, 16.5% of people experiencing homelessness had latent tuberculosis infection, 1.4% had current hepatitis B infection, 10.4% had hepatitis C infection and 1.0% had human immunodeficiency virus infection. When a quality-adjusted life-year is valued at £30,000, the latent tuberculosis screening of people experiencing homelessness was cost-effective provided treatment uptake was ≥ 25% (for a £20,000 quality-adjusted life-year threshold, treatment uptake would need to be > 50%). In prison, 12.6% of prisoners had latent tuberculosis infection, 1.9% had current hepatitis B infection, 4.2% had hepatitis C infection and 0.0% had human immunodeficiency virus infection. In both settings, levels of latent tuberculosis infection and blood-borne viruses were higher among injecting drug users. A total of 1484 prisoners were screened using chest radiography over a total of 112 screening days (new prisoner screening coverage was 43%). Twenty-nine radiographs were reported as potentially indicating tuberculosis. One prisoner began, and completed, antituberculosis treatment in prison. In the cluster randomised controlled trial of peer educators to increase screening uptake, the median uptake was 45% in the control arm and 40% in the intervention arm (adjusted risk ratio 0.98, 95% confidence interval 0.80 to 1.20). A rapid diagnostic service was established on the mobile radiographic unit but the trial of rapid diagnostics was abandoned because of recruitment and follow-up difficulties. We randomly assigned 112 patients to video-observed treatment and 114 patients to directly observed treatment. Fifty-eight per cent of those recruited had a history of homelessness, addiction, imprisonment or severe mental health problems. Seventy-eight (70%) of 112 patients on video-observed treatment achieved the primary outcome, compared with 35 (31%) of 114 patients on directly observed treatment (adjusted odds ratio 5.48, 95% confidence interval 3.10 to 9.68; p < 0.0001). Video-observed treatment was superior to directly observed treatment in all demographic and social risk factor subgroups. The cost for 6 months of treatment observation was £1645 for daily video-observed treatment, £3420 for directly observed treatment three times per week and £5700 for directly observed treatment five times per week.

Limitations

Recruitment was lower than anticipated for most of the studies. The peer advocate study may have been contaminated by the fact that the service was already using peer educators to support its work.

Conclusions

There are very high levels of latent tuberculosis infection among prisoners, people experiencing homelessness and drug users. Screening for latent infection in people experiencing homelessness alongside mobile radiographic screening would be cost-effective, providing the uptake of treatment was 25–50%. Despite ring-fenced funding, the NHS was unable to establish static radiographic screening programmes. Although we found no evidence that peer educators were more effective than health-care workers in encouraging the uptake of mobile radiographic screening, there may be wider benefits of including peer educators as part of the Find&Treat team. Utilising polymerase chain reaction-based rapid diagnostic testing on a mobile radiographic unit is feasible. Smartphone-enabled video-observed treatment is more effective and cheaper than directly observed treatment for ensuring that treatment is observed.

Future work

Trials of video-observed treatment in high-incidence settings are needed.

Trial registration

Current Controlled Trials ISRCTN17270334 and ISRCTN26184967.

Funding

This project was funded by the National Institute for Health Research (NIHR) Programme Grants for Applied Research programme and will be published in full in Programme Grants for Applied Research; Vol. 8, No. 9. See the NIHR Journals Library website for further project information.

Interferon gamma release assays for Diagnostic Evaluation of Active tuberculosis (IDEA): test accuracy study and economic evaluation

BACKGROUND

Interferon gamma release assays (IGRAs) are blood tests recommended for the diagnosis of tuberculosis (TB) infection. There is currently uncertainty about the role and clinical utility of IGRAs in the diagnostic workup of suspected active TB in routine NHS clinical practice.

OBJECTIVES

To compare the diagnostic accuracy and cost-effectiveness of T-SPOT.TB ^® (Oxford Immunotec, Abingdon, UK) and QuantiFERON^® TB GOLD In-Tube (Cellestis, Carnegie, VIC, Australia) for diagnosis of suspected active TB and to estimate the diagnostic accuracy of second-generation IGRAs.

DESIGN

Prospective within-patient comparative diagnostic accuracy study.

SETTING

Secondary care.

PARTICIPANTS

Adults (aged ≥ 16 years) presenting as inpatients or outpatients at 12 NHS hospital trusts in London, Slough, Oxford, Leicester and Birmingham with suspected active TB.

INTERVENTIONS

The index tests [T-SPOT.TB and QuantiFERON GOLD In-Tube (QFT-GIT)] and new enzyme-linked immunospot assays utilising novel Mycobacterium tuberculosis antigens (Rv3615c, Rv2654, Rv3879c and Rv3873) were verified against a composite reference standard applied by a panel of clinical experts blinded to IGRA results.

MAIN OUTCOME MEASURES

Sensitivity, specificity, predictive values and likelihood ratios were calculated to determine diagnostic accuracy. A decision tree model was developed to calculate the incremental costs and incremental health utilities [quality-adjusted life-years (QALYs)] of changing from current practice to using an IGRA as an initial rule-out test.

RESULTS

A total of 363 patients had active TB (culture-confirmed and highly probable TB cases), 439 had no active TB and 43 had an indeterminate final diagnosis. Comparing T-SPOT.TB and QFT-GIT, the sensitivities [95% confidence interval (CI)] were 82.3% (95% CI 77.7% to 85.9%) and 67.3% (95% CI 62.1% to 72.2%), respectively, whereas specificities were 82.6% (95% CI 78.6% to 86.1%) and 80.4% (95% CI 76.1% to 84.1%), respectively. T-SPOT.TB was more sensitive than QFT-GIT (relative sensitivity 1.22, 95% CI 1.14 to 1.31; p < 0.001), but the specificities were similar (relative specificity 1.02, 95% CI 0.97 to 1.08; p = 0.3). For both IGRAs the sensitivity was lower and the specificity was higher for human immunodeficiency virus (HIV)-positive than for HIV-negative patients. The most promising novel antigen was Rv3615c. The added value of Rv3615c to T-SPOT.TB was a 9% (95% CI 5% to 12%) relative increase in sensitivity at the expense of specificity, which had a relative decrease of 7% (95% CI 4% to 10%). The use of current IGRA tests for ruling out active TB is unlikely to be considered cost-effective if a QALY was valued at £20,000 or £30,000. For T-SPOT.TB, the probability of being cost-effective for a willingness to pay of £20,000/QALY was 26% and 21%, when patients with indeterminate test results were excluded or included, respectively. In comparison, the QFT-GIT probabilities were 8% and 6%. Although the use of IGRAs is cost saving, the health detriment is large owing to delay in diagnosing active TB, leading to prolonged illness. There was substantial between-patient variation in the tests used in the diagnostic pathway.

LIMITATIONS

The recruitment target for the HIV co-infected population was not achieved.

CONCLUSIONS

Although T-SPOT.TB was more sensitive than QFT-GIT for the diagnosis of active TB, the tests are insufficiently sensitive for ruling out active TB in routine clinical practice in the UK. Novel assays offer some promise.

FUTURE WORK

The novel assays require evaluation in distinct clinical settings and in immunosuppressed patient groups.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and the NIHR Health Protection Research Unit in Respiratory Infections, Imperial College London, London, UK.

Tuberculosis infection in children visiting friends and relatives in countries with high incidence of tuberculosis: A study protocol

INTRODUCTION

Tuberculosis (TB) is a global infectious disease. In low-incidence countries, paediatric TB affects mostly immigrant children and children of immigrants. We hypothesize that these children are at risk of exposure to Mycobacterium tuberculosis when they travel to the country of origin of their parents to visit friends and relatives (VFR). In this study, we aim to estimate the incidence rate and risk factors associated to latent tuberculosis infection (LTBI) and TB in VFR children.

METHODS AND ANALYSIS

A prospective study will be carried out in collaboration with 21 primary health care centres (PCC) and 5 hospitals in Catalonia, Spain. The study participants are children under 15 years of age, either immigrant themselves or born to immigrant parents, who travel to countries with high incidence of TB (≥ 40 cases/100,000 inhabitants). A sample size of 492 children was calculated. Participants will be recruited before traveling, either during a visit to a travel clinic or to their PCC, where a questionnaire including sociodemographic, epidemiological and clinical data will be completed, and a tuberculin skin test (TST) will be performed and read after 48 to 72 hours; patients with a positive TST at baseline will be excluded. A visit will be scheduled eight to twelve-weeks after their return to perform a TST and a QuantiFERON-TB Gold Plus test. The incidence rate of LTBI will be estimated per individual/month and person/year per country visited, and also by age-group.

ETHICS AND DISSEMINATION

The study protocol was approved by the Clinical Research Ethics Committee of the Hospital Universitari Mútua Terrassa (code 02/16) and the Clinical Research Ethics Committee of the Fundació Institut Universitari per a la Recerca a l'Atenció Primària de Salut Jordi Gol i Gurina (code P16/094). Articles will be published in indexed scientific journals.

TRIAL REGISTRATION

Clinical-Trials.gov: NCT04236765.

Factors associated with household contacts' tuberculosis testing and evaluation

PURPOSE

No research has been done in New York City that shows the demographic characteristics of household contacts testing, evaluation, and treatment of LTBI. The objective of the study was to identify demographic factors associated with household contacts' TB testing, evaluation, and LTBI treatment.

DESIGN AND METHODS

A retrospective analysis of the New York City (NYC) TB registry data that examined the factors (gender, age, country of birth, race/ethnicity, and borough of residence) associated with TB testing, evaluation, and LTBI treatment. The study sample included all household contacts of TB cases identified from 2010 to 2014 (N = 3,008). The data set was chosen when nurses were the primary case managers at chest centers in the department of health. Descriptive and inferential analysis was used to identify factors associated with testing, evaluation, and LTBI treatment.

RESULTS

The demographic characteristics of household contacts associated with testing, evaluation, and LTBI treatment were consistent with those of TB cases in NYC from 2010 to 2014. Those not tested, not fully evaluated, and refusing LTBI treatment were most often aged 18-44 years and were non-US born. Males were significantly more likely than females not to be fully evaluated. Among racial/ethnic groups, Asian and Hispanic persons were at higher risk of not being fully evaluated, and residents of Queens had the highest risk among the five boroughs. In multivariate analyses, age was a significant predictor of behavior, such that the older the person the less likely to get TB testing or to accept LTBI treatment. Non-US country of birth was associated with lower likelihood of being fully evaluated but more likely to accept LTBI treatment when fully evaluated, while Asian or Hispanic race/ethnicity was associated with higher likelihood of both behaviors.

CONCLUSIONS

Findings on age from this study will enable public health agencies and public health nurses to plan for effective strategies that will increase the number of household contacts who accept TB testing and evaluation, as well as the numbers who will accept and complete LTBI treatment.

The effectiveness and cost-effectiveness of screening for latent tuberculosis among migrants in the EU/EEA: a systematic review

Migrants account for a large and growing proportion of tuberculosis (TB) cases in low-incidence countries in the European Union/European Economic Area (EU/EEA) which are primarily due to reactivation of latent TB infection (LTBI). Addressing LTBI among migrants will be critical to achieve TB elimination. Methods: We conducted a systematic review to determine effectiveness (performance of diagnostic tests, efficacy of treatment, uptake and completion of screening and treatment) and a second systematic review on cost-effectiveness of LTBI screening programmes for migrants living in the EU/EEA. Results: We identified seven systematic reviews and 16 individual studies that addressed our aims. Tuberculin skin tests and interferon gamma release assays had high sensitivity (79%) but when positive, both tests poorly predicted the development of active TB (incidence rate ratio: 2.07 and 2.40, respectively). Different LTBI treatment regimens had low to moderate efficacy but were equivalent in preventing active TB. Rifampicin-based regimens may be preferred because of lower hepatotoxicity (risk ratio = 0.15) and higher completion rates (82% vs 69%) compared with isoniazid. Only 14.3% of migrants eligible for screening completed treatment because of losses along all steps of the LTBI care cascade. Limited economic analyses suggest that the most cost-effective approach may be targeting young migrants from high TB incidence countries. Discussion: The effectiveness of LTBI programmes is limited by the large pool of migrants with LTBI, poorly predictive tests, long treatments and a weak care cascade. Targeted LTBI programmes that ensure high screening uptake and treatment completion will have greatest individual and public health benefit.

Detailed characterisation of the tuberculosis epidemic in Western Sydney: a descriptive epidemiological study

Traditional tuberculosis (TB) epidemiology reports rarely provide a detailed analysis of TB incidence in particular geographic locations and among diverse population groups. Western Sydney Local Health District (WSLHD) has one of the highest TB incidence rates in Australia, and we explored whether more detailed epidemiological analysis could provide a better overview of the local disease dynamics.

Using multiple relevant data sources, we performed a retrospective descriptive study of TB cases diagnosed within the WSLHD from 2006 to 2015 with a specific focus on geographic hotspots and the population structure within these hotspots.

Over the study period nearly 90% of Western Sydney TB cases were born in a high TB incidence country. The TB disease burden was geographically concentrated in particular areas, with variable ethnic profiles in these different hotspots. The most common countries of birth were India (33.0%), the Philippines (11.4%) and China (8.8%). Among the local government areas in Western Sydney, Auburn had the highest average TB incidence (29.4 per 100 000) with exceptionally high population-specific TB incidence rates among people born in Nepal (average 223 per 100 000 population), Afghanistan (average 154 per 100 000 population) and India (average 143 per 100 000 population).

Similar to other highly cosmopolitan cities around the world, the TB burden in Sydney showed strong geographic concentration. Detailed analysis of TB patient and population profiles in Western Sydney should guide better contextualised and culturally appropriate public health strategies.

High migration from tuberculosis (TB)-endemic settings to Western Sydney is driving over-representation among TB cases of specific cultural groups within geographic “hotspots”, requiring contextualised and culturally appropriate public health strategieshttp://bit.ly/2LqusU9

Defining a migrant-inclusive tuberculosis research agenda to end TB

BACKGROUND

Pillar 3 of the End TB Strategy calls for the promotion of research and innovation at the country level to facilitate improved implementation of existing and novel interventions to end tuberculosis (TB). In an era of increasing cross-border migration, there is a specific need to integrate migration-related issues into national TB research agendas. The objective of the present review is to provide a conceptual framework to guide countries in the development and operationalization of a migrant-inclusive TB research agenda.

METHODS

We conducted a literature review, complemented by expert opinion and the previous articles in this State of the Art series, to identify important themes central to migration-related TB. We categorized these themes into a framework for a migration-inclusive global TB research agenda across a comprehensive spectrum of research. We developed this conceptual framework taking into account: 1) the biomedical, social and structural determinants of TB; 2) the epidemiologic impact of the migration pathway; and 3) the feasibility of various types of research based on a country's capacity.

DISCUSSION

The conceptual framework presented here is based on the key principle that migrants are not inherently different from other populations in terms of susceptibility to known TB determinants, but that they often have exacerbated or additional risks related to their country of origin and the migration process, which must be accounted for in developing comprehensive TB prevention and care strategies. A migrant-inclusive research agenda should systematically consider this wider context to have the highest impact.

Two interferon gamma release assays for predicting active tuberculosis: the UK PREDICT TB prognostic test study

BACKGROUND

Despite a recent decline in the annual incidence of tuberculosis (TB) in the UK, rates remain higher than in most Western European countries. The detection and treatment of latent TB infection (LTBI) is an essential component of the UK TB control programme.

OBJECTIVES

To assess the prognostic value and cost-effectiveness of the current two interferon gamma release assays (IGRAs) compared with the standard tuberculin skin test (TST) for predicting active TB among untreated individuals at increased risk of TB: (1) contacts of active TB cases and (2) new entrants to the UK from high-TB-burden countries.

DESIGN

A prospective cohort study and economic analysis.

PARTICIPANTS AND SETTING

Participants were recruited in TB clinics, general practices and community settings. Contacts of active TB cases and migrants who were born in high-TB-burden countries arriving in the UK were eligible to take part if they were aged ≥ 16 years.

MAIN OUTCOME MEASURES

Outcomes include incidence rate ratios comparing the incidence of active TB in those participants with a positive test result and those with a negative test result for each assay, and combination of tests and the cost per quality-adjusted life-year (QALY) for each screening strategy.

RESULTS

A total of 10,045 participants were recruited between May 2010 and July 2015. Among 9610 evaluable participants, 97 (1.0%) developed active TB. For the primary analysis, all test data were available for 6380 participants, with 77 participants developing active TB. A positive result for TST^a (positive if induration is ≥ 5 mm) was a significantly poorer predictor of progression to active TB than a positive result for any of the other tests. Compared with TST^b [positive if induration is ≥ 6 mm without prior bacillus Calmette-Guérin (BCG) alone, T-SPOT^®.TB (Oxford Immunotec Ltd, Oxford, UK), TST^a + T-SPOT.TB, TST^a + IGRA and the three combination strategies including TST^b were significantly superior predictors of progression. Compared with the T-SPOT.TB test alone, TST^a + T-SPOT.TB, TST^b + QuantiFERON^® TB Gold In-Tube (QFT-GIT; QIAGEN GmbH, Hilden, Germany) and TST^b + IGRA were significantly superior predictors of progression and, compared with QFT-GIT alone, T-SPOT.TB, TST^a + T-SPOT.TB, TST^a + QFT-GIT, TST^a + IGRA, TST^b + T-SPOT.TB, TST^b + QFT-GIT and TST^b + IGRA were significantly superior predictors of progression. When evaluating the negative predictive performance of tests and strategies, negative results for TST^a + QFT-GIT were significantly poorer predictors of non-progression than negative results for TST^a, T-SPOT.TB and TST^a + IGRA. The most cost-effective LTBI testing strategies are the dual-testing strategies. The cost and QALY differences between the LTBI testing strategies were small; in particular, QFT-GIT, TST^b + T-SPOT.TB and TST^b + QFT-GIT had very similar incremental net benefit estimates.

CONCLUSION

This study found modest differences between tests, or combinations of tests, in identifying individuals who would go on to develop active TB. However, a two-step approach that combined TST^b with an IGRA was the most cost-effective testing option.

IMPLICATIONS FOR PRACTICE AND FUTURE RESEARCH

The two-step TST^b strategy, which stratified the TST by prior BCG vaccination followed by an IGRA, was the most cost-effective approach. The limited ability of current tests to predict who will progress limits the clinical utility of tests. The implications of these results for the NHS England/Public Health England national TB screening programme for migrants should be investigated.

STUDY REGISTRATION

This study is registered as NCT01162265.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Community-based testing of migrants for infectious diseases (COMBAT-ID): impact, acceptability and cost-effectiveness of identifying infectious diseases among migrants in primary care: protocol for an interrupted time-series, qualitative and health economic analysis

BACKGROUND

Migration is a major global driver of population change. Certain migrants may be at increased risk of infectious diseases, including tuberculosis (TB), HIV, hepatitis B and hepatitis C, and have poorer outcomes. Early diagnosis and management of these infections can reduce morbidity, mortality and onward transmission and is supported by national guidelines. To date, screening initiatives have been sporadic and focused on individual diseases; systematic routine testing of migrant groups for multiple infections is rarely undertaken and its impact is unknown. We describe the protocol for the evaluation of acceptability, effectiveness and cost-effectiveness of an integrated approach to screening migrants for a range of infectious diseases in primary care.

METHODS AND ANALYSIS

We will conduct a mixed-methods study which includes an observational cohort with interrupted time-series analysis before and after the introduction of routine screening of migrants for infectious diseases (latent TB, HIV, hepatitis B and hepatitis C) when first registering with primary care within Leicester, UK. We will assess trends in the monthly number and rate of testing and diagnosis for latent TB, HIV, hepatitis B and hepatitis C to determine the effect of the policy change using segmented regression analyses at monthly time-points. Concurrently, we will undertake an integrated qualitative sub-study to understand the views of migrants and healthcare professionals to the new testing policy in primary care. Finally, we will evaluate the cost-effectiveness of combined infection testing for migrants in primary care.

ETHICS AND DISSEMINATION

The study has received HRA and NHS approvals for both the interrupted time-series analysis (16/SC/0127) and the qualitative sub-study (16/EM/0159). For the interrupted time-series analysis we will only use fully anonymised data. For the qualitative sub-study, we will gain written, informed, consent. Dissemination of the results will be through local and national meetings/conferences as well as publications in peer-reviewed journals.

Immigrant screening for latent tuberculosis infection: numbers needed to test and treat, a Norwegian population-based cohort study

OBJECTIVES

To estimate the number needed to screen (NNS) and the number needed to treat (NNT) to prevent one tuberculosis (TB) case in the Norwegian immigrant latent tuberculosis infection (LTBI) screening programme and to explore the effect of delay of LTBI treatment initiation.

DESIGN

Population-based, prospective cohort study.

PARTICIPANTS

Immigrants to Norway.

OUTCOME

Incident TB.

METHODS

We obtained aggregated data on immigration to Norway in 2008-2011 and used data from the Norwegian Surveillance System for Infectious Diseases to assess the number of TB cases arising in this cohort within 5 years after arrival. We calculated the average NNS and NNT for immigrants from the top 10 source countries for TB in Norway and by estimated TB incidence rates in source countries. We explored the sensitivity of these estimates with regard to test performance, treatment efficacy and treatment adherence using an extreme value approach, and assessed the effects of emigration, time to TB diagnosis (to define incident TB) and intervention timing.

RESULTS

NNS and NNT were overall high, with substantial variation. NNT showed numerically stronger negative correlation with TB notification rate in Norway (-0.75 [95% CI -1.00 to -0.44]) than with the WHO incidence rate (IR) (-0.32 [95% CI -0.93 to 0.29]). NNT was affected substantially by emigration and the definition of incident TB. Estimates were lowest for Somali (NNS 99 [70-150], NNT 27 [19-41]) and highest for Thai immigrants (NNS 585 [413-887], NNT 111 [79-116]). Implementing LTBI treatment in immigrants sooner after arrival may improve the effectiveness of the programme.

CONCLUSION

Using TB notifications in Norway, rather than IR in source countries, would improve targeting of immigrants for LTBI management. However, the overall high NNT is a concern and challenges the scale-up of preventive LTBI treatment for significant public health impact. Better data are urgently needed to monitor and evaluate NNS and NNT in countries implementing LTBI screening.

Estimating the prevalence of latent tuberculosis in a low-incidence setting: Australia

Migration is a key driver of tuberculosis (TB) in many low-incidence settings, with the majority of TB cases attributed to reactivation of latent TB (LTBI) acquired overseas. A greater understanding of LTBI risk in heterogeneous migrant populations would aid health planning. We aimed to estimate the LTBI prevalence and distribution among locally born and overseas-born Australians.

Annual risks of TB infection estimates were applied to population cohorts (by country of birth, year of arrival and age) in Australian census data in 2006, 2011 and 2016.

Both the absolute number and proportion of Australian residents with LTBI increased from 4.6% (interquartile range (IQR) 4.2–5.2%) in 2006 to 5.1% (IQR 4.7–5.5%) in 2016, due to the increasing proportion of the population born overseas (23.8% in 2006 to 28.3% in 2016). Of all residents estimated to have LTBI in 2016; 93.2% were overseas born, 21.6% were aged <35 years and 34.4% had migrated to Australia since 2007.

The overall prevalence of LTBI in Australia is low. Some residents, particularly migrants from high-incidence settings, may have considerably higher risk of LTBI, and these findings allow for tailored public health interventions to reduce the risk and impact of future TB disease.

Economic analysis of CDC's culture- and smear-based tuberculosis instructions for Filipino immigrants

SETTING

In 2007, the US Centers for Disease Control and Prevention (CDC) revised its tuberculosis (TB) technical instructions for panel physicians who administer mandatory medical examinations among US-bound immigrants. Many US-bound immigrants come from the Philippines, a high TB prevalence country.

OBJECTIVE

To quantify economic and health impacts of smear- vs. culture-based TB screening.

DESIGN

Decision tree modeling was used to compare three Filipino screening programs: 1) no screening, 2) smear-based screening, and 3) culture-based screening. The model incorporated pre-departure TB screening results from Filipino panel physicians and CDC databases with post-arrival follow-up outcomes. Costs (2013 $US) were examined from societal, immigrant, US Public Health Department and hospitalization perspectives.

RESULTS

With no screening, an annual cohort of 35 722 Filipino immigrants would include an estimated 450 TB patients with 264 hospitalizations, at a societal cost of US$9.90 million. Culture-based vs. smear-based screening would result in fewer imported cases (80.9 vs. 310.5), hospitalizations (19.7 vs. 68.1), and treatment costs (US$1.57 million vs. US$4.28 million). Societal screening costs, including US follow-up, were greater for culture-based screening (US$5.98 million) than for smear-based screening (US$3.38 million). Culture-based screening requirements increased immigrant costs by 61% (US$1.7 million), but reduced costs for the US Public Health Department (22%, US$750 000) and of hospitalization (70%, US$1 020 000).

CONCLUSION

Culture-based screening reduced imported TB and US costs among Filipino immigrants.

Accurate diagnosis of latent tuberculosis in children, people who are immunocompromised or at risk from immunosuppression and recent arrivals from countries with a high incidence of tuberculosis: systematic review and economic evaluation

BACKGROUND

Tuberculosis (TB), caused by Mycobacterium tuberculosis (MTB) [(Zopf 1883) Lehmann and Neumann 1896], is a major cause of morbidity and mortality. Nearly one-third of the world's population is infected with MTB; TB has an annual incidence of 9 million new cases and each year causes 2 million deaths worldwide.

OBJECTIVES

To investigate the clinical effectiveness and cost-effectiveness of screening tests [interferon-gamma release assays (IGRAs) and tuberculin skin tests (TSTs)] in latent tuberculosis infection (LTBI) diagnosis to support National Institute for Health and Care Excellence (NICE) guideline development for three population groups: children, immunocompromised people and those who have recently arrived in the UK from high-incidence countries. All of these groups are at higher risk of progression from LTBI to active TB.

DATA SOURCES

Electronic databases including MEDLINE, EMBASE, The Cochrane Library and Current Controlled Trials were searched from December 2009 up to December 2014.

REVIEW METHODS

English-language studies evaluating the comparative effectiveness of commercially available tests used for identifying LTBI in children, immunocompromised people and recent arrivals to the UK were eligible. Interventions were IGRAs [QuantiFERON(®)-TB Gold (QFT-G), QuantiFERON(®)-TB Gold-In-Tube (QFT-GIT) (Cellestis/Qiagen, Carnegie, VA, Australia) and T-SPOT.TB (Oxford Immunotec, Abingdon, UK)]. The comparator was TST 5 mm or 10 mm alone or with an IGRA. Two independent reviewers screened all identified records and undertook a quality assessment and data synthesis. A de novo model, structured in two stages, was developed to compare the cost-effectiveness of diagnostic strategies.

RESULTS

In total, 6687 records were screened, of which 53 unique studies were included (a further 37 studies were identified from a previous NICE guideline). The majority of the included studies compared the strength of association for the QFT-GIT/G IGRA with the TST (5 mm or 10 mm) in relation to the incidence of active TB or previous TB exposure. Ten studies reported evidence on decision-analytic models to determine the cost-effectiveness of IGRAs compared with the TST for LTBI diagnosis. In children, TST (≥ 5 mm) negative followed by QFT-GIT was the most cost-effective strategy, with an incremental cost-effectiveness ratio (ICER) of £18,900 per quality-adjusted life-year (QALY) gained. In immunocompromised people, QFT-GIT negative followed by the TST (≥ 5 mm) was the most cost-effective strategy, with an ICER of approximately £18,700 per QALY gained. In those recently arrived from high TB incidence countries, the TST (≥ 5 mm) alone was less costly and more effective than TST (≥ 5 mm) positive followed by QFT-GIT or T-SPOT.TB or QFT-GIT alone.

LIMITATIONS

The limitations and scarcity of the evidence, variation in the exposure-based definitions of LTBI and heterogeneity in IGRA performance relative to TST limit the applicability of the review findings.

CONCLUSIONS

Given the current evidence, TST (≥ 5 mm) negative followed by QFT-GIT for children, QFT-GIT negative followed by TST (≥ 5 mm) for the immunocompromised population and TST (≥ 5 mm) for recent arrivals were the most cost-effective strategies for diagnosing LTBI that progresses to active TB. These results should be interpreted with caution given the limitations identified. The evidence available is limited and more high-quality research in this area is needed including studies on the inconsistent performance of tests in high-compared with low-incidence TB settings; the prospective assessment of progression to active TB for those at high risk; the relative benefits of two-compared with one-step testing with different tests; and improved classification of people at high and low risk for LTBI.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42014009033.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Completion Rate and Safety of Tuberculosis Infection Treatment With Shorter Regimens

BACKGROUND

The traditional treatment of tuberculosis (TB) infection (9 months of daily isoniazid [9H]) is safe but completion rates of <50% are reported. Shorter regimens (3 months of once-weekly isoniazid and rifapentine [3HP] or 4 months of daily rifampin [4R]) are associated with improved adherence in adults.

METHODS

This was a retrospective cohort study (2014-2017) of children (0-18 years old) seen at a children's TB clinic in a low-incidence nation. We compared the frequency of completion and adverse events (AEs) in children receiving 3HP, 4R, and 9H; the latter 2 regimens could be administered by families (termed self-administered therapy [SAT]) or as directly observed preventive therapy (DOPT); 3HP was always administered under DOPT.

RESULTS

TB infection treatment was started in 667 children: 283 (42.4%) 3HP, 252 (37.8%) 9H, and 132 (19.8%) 4R. Only 52% of children receiving 9H via SAT completed therapy. Children receiving 3HP were more likely to complete therapy than the 9H (SAT) group (odds ratio [OR] 27.4, 95% confidence interval [CI]: 11.8-63.7). Multivariate analyses found receipt of medication under DOPT (OR: 5.72, 95% CI: 3.47-9.43), increasing age (OR: 1.09, 95% CI: 1.02-1.17), and the absence of any AE (OR: 1.70, 95% CI: 0.26-0.60) to be associated with completing therapy. AEs were more common in the 9H group (OR: 2.51, 95% CI: 1.48-4.32). Two (0.9%) children receiving 9H developed hepatotoxicity; no child receiving 3HP or 4R developed hepatotoxicity.

CONCLUSIONS

Shorter regimens are associated with increased completion rates and fewer AEs than 9H.

National roll-out of latent tuberculosis testing and treatment for new migrants in England: a retrospective evaluation in a high-incidence area

Latent tuberculosis infection (LTBI) screening is an important intervention for tuberculosis (TB) elimination in low-incidence countries and is, therefore, a key component of England's TB control strategy. This study describes outcomes from a LTBI screening programme in a high-incidence area to inform national LTBI screening in England and other low-incidence countries.We conducted a retrospective cohort study of LTBI screening among eligible migrants (from high-incidence countries and entered the UK within the last 5 years), who were identified at primary-care clinics in Newham, London between August 2014 and August 2015. Multivariable logistic regression was used to identify factors associated with LTBI testing uptake, interferon-γ release assay (IGRA) positivity and treatment uptake.40% of individuals offered LTBI screening received an IGRA test. The majority of individuals tested were 16-35 years old, male and born in India, Bangladesh or Pakistan. Country of birth, smoking status and co-morbidities were associated with LTBI testing uptake. IGRA positivity was 32% among those tested and was significantly associated with country of birth, age, sex and co-morbidities.This study identifies factors associated with screening uptake, IGRA positivity and treatment uptake, and improves understanding of groups that should be supported to increase acceptability of LTBI testing and treatment in the community.

[Screening program for tuberculosis among international exchange students in the Department of Isère]

INTRODUCTION

France is a low-incidence country for tuberculosis (TB). Consequently screening is focused on high-risk populations, in particular migrants. The aim of this study was to evaluate the epidemiology of TB among international exchange students in the Department of Isère and the screening programs used.

METHODS

We carried out an organizational audit based on interviews with physicians involved in the management of TB in Isère. We conducted a retrospective descriptive study based on a case series of foreign students treated for TB from 2003 to 2013 inclusively.

RESULTS

Forty-six international exchange students were treated for active TB during this time, representing an average incidence of 284/100,000. Two thirds of our studied population were Africans, 72% were asymptomatic at the time of screening. A quarter of our cohort developed TB after the initial screening. Thirty-one cases were confirmed bacteriologically, mainly through bronchoscopy. Outcome (radiological and clinical) on quadruple therapy was satisfactory in all patients. Two patients relapsed, one of them with multi-drug resistant TB.

CONCLUSION

Our work confirms that international exchange students are a population at high risk of TB and that screening of this population is essential. The significant number of active TB cases diagnosed after the initial screening stresses the importance of diagnosis and follow up of patients with latent TB infection.

Comparing tuberculin skin test and interferon γ release assay (T-SPOT.TB) to diagnose latent tuberculosis infection in household contacts

BACKGROUND/AIMS

The tuberculin skin test (TST) and interferon γ release assay are currently used as diagnostic tools to detect latent tuberculosis (TB) infection; however, there are inconsistencies about the degree of agreement between the tests. We aimed to evaluate the concordance rate between the two tests in household contacts of a country with intermediate TB burden, where most people were vaccinated.

METHODS

We recruited household contacts who spent > 8 hours daily with patients with microbiologically confirmed active pulmonary TB, and received both TST and T-SPOT.TB (Oxford Immunotec) simultaneously. The degree of agreement was analysed according to TST cutoff and Bacille Calmette-Guerin (BCG) vaccination status. Relevant factors were analysed to establish the association with TST or T-SPOT.TB.

RESULTS

Among 298 household contacts, 122 (40.9%) were spouses, and 250 (83.9%) had received BCG vaccination. In the contact sources, 117 (39.3%) showed a positive result for acid-fast bacillus (AFB) sputum smear and 109 (36.6%) had cavities. The highest agreement rate of 69.5% and κ value of 0.378 were found with a 10 mm cutoff. Spouse, time interval from TB diagnosis to test, and AFB sputum smear positivity were significantly associated with a positive result for T-SPOT.TB. Sex, BCG vaccination, and cavity on chest computed tomography were related to TST positivity.

CONCLUSIONS

The present study suggested it was not possible for TST and T-SPOT.TB to replace each other because of considerable discrepancy between the two tests in household contacts in a country with intermediate TB prevalence.

Predicting tuberculosis risk in the foreign-born population of British Columbia, Canada: study protocol for a retrospective population-based cohort study

INTRODUCTION

Improved understanding of risk factors for developing active tuberculosis (TB) will better inform decisions about diagnostic testing and treatment for latent TB infection (LTBI) in migrant populations in low-incidence regions. We aim to examine TB risk factors among the foreign-born population in British Columbia (BC), Canada, and to create and validate a clinically relevant multivariate risk score to predict active TB.

METHODS AND ANALYSIS

This retrospective population-based cohort study will include all foreign-born individuals who acquired permanent resident status in Canada between 1 January 1985 and 31 December 2013 and acquired healthcare coverage in BC at any point during this period. Multiple administrative databases and disease registries will be linked, including a National Immigration Database, BC Provincial Health Insurance Registration, physician billings, hospitalisations, drugs dispensed from community pharmacies, vital statistics, HIV testing and notifications, cancer, chronic kidney disease and dialysis treatment, and all TB and LTBI testing and treatment data in BC. Extended proportional hazards regression will be used to estimate risk factors for TB and to create a prognostic TB risk score.

ETHICS AND DISSEMINATION

Ethical approval for this study has been obtained from the University of British Columbia Clinical Ethics Review Board. Once completed, study findings will be presented at conferences and published in peer-reviewed journals. An online TB risk score calculator will also be created.

Relation between BCG vaccine scar and an interferon-gamma release assay in immigrant children with "positive" tuberculin skin test (≥10 mm)

Background

Immigrants from countries with high incidence of tuberculosis (TB) are usually offered screening when they arrive to low incidence countries. The tuberculin skin test (TST) is often used. The interferon gamma release assays (IGRAs) are more specific and not affected by BCG vaccination. The aims of this study were 1. To see if there if there is a correlation between a positive IGRA (QFT) and presence of a BCG scar in children with TST ≥10 mm, 2. To compare the TST diameter with QFT result, 3. To see if chest X-ray can be omitted in QFT negative children despite TST ≥10 mm.

Methods

762 healthy children/adolescents (median age 14 years) arriving to Gothenburg and surroundings with TST ≥10 mm were tested with QFT.

Results

A total of 163/492 (33 %) children with BCG scar had positive QFT, whereas 205/270 (76 %) without BCG scar had positive QFT (p < 0.0001). The median TST was 12 mm in QFT negative and 18 mm in QFT positive children (p < 0.0001) but with considerable overlap. Median TST was the same (12 mm) in QFT negative children with and without BCG scar. Among the QFT positive children 25/368 had chest X-ray changes compared to 2/393 among the QFT negative children (p < 0.0007).

Conclusions

Previous BCG vaccination had an effect on the TST diameter so an IGRA is recommended to diagnose latent TB. Using only TST for screening of latent TB would lead to overdiagnosis. The TST diameter was larger in QFT positive than in QFT negative children but could not predict QFT in the individual patient. Chest X ray contributes little to the diagnosis of TB in QFT negative children but can not be omitted because of late seroconversion of QFT in some patients.

Trial registration

Not applicable.

Diagnosis of Ocular Tuberculosis

Ocular tuberculosis remains a presumptive clinical diagnosis, as the gold standard tests for diagnosing ocular tuberculosis are often not useful: Mycobacterium tuberculosis cultures require weeks to process on Lowenstein-Jenson media and have low yield from ocular samples; while acid-fast bacilli smears or polymerase chain reaction detection of M. tuberculosis DNA have low sensitivities. Thus, diagnosis is often based on suggestive clinical signs, which are supported by positive investigations: tuberculin skin test or interferon-gamma release assays; chest X-ray findings suggestive of pulmonary tuberculosis, and/or evidence of associated systemic tuberculosis infections in the absence of other underlying disease. The aim of this review is to provide an update on the methods of diagnosing ocular tuberculosis, and discuss the challenges of its diagnosis. We also suggest a step-ladder approach to a more accurate diagnosis of ocular tuberculosis by combining the available diagnostic tests.

Improving Control of Tuberculosis in Low-Burden Countries: Insights from Mathematical Modeling

Tuberculosis control and elimination remains a challenge for public health even in low-burden countries. New technology and novel approaches to case-finding, diagnosis, and treatment are causes for optimism but they need to be used cost-effectively. This in turn requires improved understanding of the epidemiology of TB and analysis of the effectiveness and cost-effectiveness of different interventions. We describe the contribution that mathematical modeling can make to understanding epidemiology and control of TB in different groups, guiding improved approaches to public health interventions. We emphasize that modeling is not a substitute for collecting data but rather is complementary to empirical research, helping determine what are the key questions to address to maximize the public-health impact of research, helping to plan studies, and making maximal use of available data, particularly from surveillance, and observational studies. We provide examples of how modeling and related empirical research inform policy and discuss how a combination of these approaches can be used to address current questions of key importance, including use of whole-genome sequencing, screening and treatment for latent infection, and combating drug resistance.

Outcomes analysis of new entrant screening for active tuberculosis in Heathrow and Gatwick airports, United Kingdom 2009/2010

Background

In 2012, the United Kingdom (UK) Government announced that the new entrant screening for active tuberculosis (TB) in Heathrow and Gatwick airports would end. Our study objective was to estimate screening yield and diagnostic accuracy, and identify those at risk of active TB after entry.

Methods

We designed a retrospective cohort study and linked new entrants screened from June 2009 to September 2010 through probabilistic matching with UK Enhanced TB Surveillance (ETS) data (June 2009 to December 2010). Yield was the proportion of cases reported to ETS within three months of airport screening in the screened population. To estimate screening diagnostic accuracy we assessed sensitivity, specificity, positive and negative predictive values. Through Poisson regression we identified groups at increased risk of TB diagnosis after entry.

Results

We identified 200,199 screened entrants, of these 59 had suspected TB at screening and were reported within 3 months to ETS (yield = 0.03 %). Sensitivity was 26 %; specificity was 99.7 %; positive predictive value was 13.2 %; negative predictive value was 99.9 %. Overall, 350 entrants were reported in ETS. Persons from countries with annual TB incidence higher than 150 cases per 100,000 population and refugees and asylum seekers were at increased risk of TB diagnosis after entry (population attributable risk 77 and 3 % respectively).

Conclusion

Airport screening has very low screening yields, sensitivity and positive predictive value. New entrants coming from countries with annual TB incidence higher than 150 per 100,000 population, refugees and asylum seekers should be prioritised at pre- or post-entry screening.

The impact of migration on tuberculosis epidemiology and control in high-income countries: a review

Tuberculosis (TB) causes significant morbidity and mortality in high-income countries with foreign-born individuals bearing a disproportionate burden of the overall TB case burden in these countries. In this review of tuberculosis and migration we discuss the impact of migration on the epidemiology of TB in low burden countries, describe the various screening strategies to address this issue, review the yield and cost-effectiveness of these programs and describe the gaps in knowledge as well as possible future solutions.The reasons for the TB burden in the migrant population are likely to be the reactivation of remotely-acquired latent tuberculosis infection (LTBI) following migration from low/intermediate-income high TB burden settings to high-income, low TB burden countries.TB control in high-income countries has historically focused on the early identification and treatment of active TB with accompanying contact-tracing. In the face of the TB case-load in migrant populations, however, there is ongoing discussion about how best to identify TB in migrant populations. In general, countries have generally focused on two methods: identification of active TB (either at/post-arrival or increasingly pre-arrival in countries of origin) and secondly, conditionally supported by WHO guidance, through identifying LTBI in migrants from high TB burden countries. Although health-economic analyses have shown that TB control in high income settings would benefit from providing targeted LTBI screening and treatment to certain migrants from high TB burden countries, implementation issues and barriers such as sub-optimal treatment completion will need to be addressed to ensure program efficacy.

High Discordance Between Pre-US and Post-US Entry Tuberculosis Test Results Among Immigrant Children: Is it Time to Adopt Interferon Gamma Release Assay for Preentry Tuberculosis Screening?

BACKGROUND

Since 2007, immigration applicants 2-14 years old with a tuberculin skin test (TST) ≥10 mm and an otherwise negative evaluation for tuberculosis (TB) are assigned a classification for TB infection and instructed to seek domestic evaluation upon arrival in the US in accordance with Centers for Disease Control and Prevention instructions. We examined the characteristics and outcome of domestic evaluation of immigrant children who arrived in California with a positive TST on preimmigration examination to inform the preimmigration TB screening process.

METHODS

Retrospective analysis of the characteristics and results of domestic evaluation of immigrants 2-14 years old who arrived in California with a classification for TB infection during October 1, 2008-September 30, 2013 was performed. TB disease was determined by matching preimmigration records with the California TB registry.

RESULTS

Among a total of 12,544 immigrant children included, 7786 (62%) were evaluated for TB postentry. Of these, 5243 (67%) were tested with TST or interferon gamma release assay (IGRA), and 2371 (45%) had a positive test. Of those tested with IGRA (n = 4035), 914 (23%) were positive. The proportion with positive IGRA increased significantly with age (years): 2-4 (11%), 5-9 (19%), 10-14 (28%), P < 0.0001; was lowest among arrivers from China (6%) and highest among arrivers from Mexico (48%). Nine children (0.07%) had TB disease within 5 years after arrival.

CONCLUSIONS

The majority of immigrant children with a positive preimmigration TST tested negative for TB infection on domestic evaluation using TST or IGRA. Inclusion of IGRA in preimmigration TB screening is likely to reduce subsequent testing, treatment and cost of evaluations among immigrant children to the US.

Methods Used in Economic Evaluations of Tuberculin Skin Tests and Interferon Gamma Release Assays for the Screening of Latent Tuberculosis Infection: A Systematic Review

BACKGROUND

Latent tuberculosis infection (LTBI) provides a constant pool of new active tuberculosis cases; a third of the earth's population is estimated to be infected with LTBI.

OBJECTIVE

The objective of this systematic review was to assess the quality and summarize the available evidence from published economic evaluations reporting on the cost-effectiveness of tuberculin skin tests (TSTs) compared with interferon gamma release assays (IGRAs) for the screening of LTBI.

METHODS

An extensive systematic review of the published literature was conducted. A two-step process was adopted to identify relevant articles: information was extracted into evidence tables and then analyzed. The quality of the publications was assessed using a 10-item checklist specific for economic evaluations.

RESULTS

Twenty-eight studies were identified for inclusion in this review. Most of the studies found IGRAs to be more cost-effective than TSTs; however, the conclusions from the studies varied significantly. Most studies scored highly on the checklist although only one fulfilled all the stipulated criteria. A wide variety of methodological approaches were documented; identified differences included the type of economic evaluation and model, time horizon, perspective, and outcomes measures.

CONCLUSIONS

The lack of consistent methods across studies makes it difficult to draw any firm conclusions about the most cost-effective option between TSTs and IGRAs. This problem can be solved by improving the quality of economic evaluation studies in the field of LTBI screening, through adherence to quality checklists.

Systematic review, meta-analysis and economic modelling of molecular diagnostic tests for antibiotic resistance in tuberculosis

BACKGROUND

Drug-resistant tuberculosis (TB), especially multidrug-resistant (MDR, resistance to rifampicin and isoniazid) disease, is associated with a worse patient outcome. Drug resistance diagnosed using microbiological culture takes days to weeks, as TB bacteria grow slowly. Rapid molecular tests for drug resistance detection (1 day) are commercially available and may promote faster initiation of appropriate treatment.

OBJECTIVES

To (1) conduct a systematic review of evidence regarding diagnostic accuracy of molecular genetic tests for drug resistance, (2) conduct a health-economic evaluation of screening and diagnostic strategies, including comparison of alternative models of service provision and assessment of the value of targeting rapid testing at high-risk subgroups, and (3) construct a transmission-dynamic mathematical model that translates the estimates of diagnostic accuracy into estimates of clinical impact.

REVIEW METHODS AND DATA SOURCES

A standardised search strategy identified relevant studies from EMBASE, PubMed, MEDLINE, Bioscience Information Service (BIOSIS), System for Information on Grey Literature in Europe Social Policy & Practice (SIGLE) and Web of Science, published between 1 January 2000 and 15 August 2013. Additional 'grey' sources were included. Quality was assessed using quality assessment of diagnostic accuracy studies version 2 (QUADAS-2). For each diagnostic strategy and population subgroup, a care pathway was constructed to specify which medical treatments and health services that individuals would receive from presentation to the point where they either did or did not complete TB treatment successfully. A total cost was estimated from a health service perspective for each care pathway, and the health impact was estimated in terms of the mean discounted quality-adjusted life-years (QALYs) lost as a result of disease and treatment. Costs and QALYs were both discounted at 3.5% per year. An integrated transmission-dynamic and economic model was used to evaluate the cost-effectiveness of introducing rapid molecular testing (in addition to culture and drug sensitivity testing). Probabilistic sensitivity analysis was performed to evaluate the impact on cost-effectiveness of diagnostic and treatment time delays, diagnosis and treatment costs, and associated QALYs.

RESULTS

A total of 8922 titles and abstracts were identified, with 557 papers being potentially eligible. Of these, 56 studies contained sufficient test information for analysis. All three commercial tests performed well when detecting drug resistance in clinical samples, although with evidence of heterogeneity between studies. Pooled sensitivity for GenoType® MTBDRplus (Hain Lifescience, Nehren, Germany) (isoniazid and rifampicin resistance), INNO-LiPA Rif.TB® (Fujirebio Europe, Ghent, Belgium) (rifampicin resistance) and Xpert® MTB/RIF (Cepheid Inc., Sunnyvale, CA, USA) (rifampicin resistance) was 83.4%, 94.6%, 95.4% and 96.8%, respectively; equivalent pooled specificity was 99.6%, 98.2%, 99.7% and 98.4%, respectively. Results of the transmission model suggest that all of the rapid assays considered here, if added to the current diagnostic pathway, would be cost-saving and achieve a reduction in expected QALY loss compared with current practice. GenoType MTBDRplus appeared to be the most cost-effective of the rapid tests in the South Asian population, although results were similar for GeneXpert. In all other scenarios GeneXpert appeared to be the most cost-effective strategy.

CONCLUSIONS

Rapid molecular tests for rifampicin and isoniazid resistance were sensitive and specific. They may also be cost-effective when added to culture drug susceptibility testing in the UK. There is global interest in point-of-care testing and further work is needed to review the performance of emerging tests and the wider health-economic impact of decentralised testing in clinics and primary care, as well as non-health-care settings, such as shelters and prisons.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42011001537.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Updates on the risk factors for latent tuberculosis reactivation and their managements

The preventive treatment of latent tuberculosis infection (LTBI) is of great importance for the elimination and control of tuberculosis (TB) worldwide, but existing screening methods for LTBI are still limited in predicting the onset of TB. Previous studies have found that some high-risk factors (including human immunodeficiency virus (HIV), organ transplantation, silicosis, tumor necrosis factor-alpha blockers, close contacts and kidney dialysis) contribute to a significantly increased TB reactivation rate. This article reviews each risk factor's association with TB and approaches to address those factors. Five regimens are currently recommended by the World Health Organization, and no regimen has shown superiority over others. In recent years, studies have gradually narrowed down to the preventive treatment of LTBI for high-risk target groups, such as silicosis patients, organ-transplantation recipients and HIV-infected patients. This review discusses regimens for each target group and compares the efficacy of different regimens. For HIV patients and transplant recipients, isoniazid monotherapy is effective in treating LTBI, but for others, little evidence is available at present.

A scoping review of cost-effectiveness of screening and treatment for latent tubercolosis infection in migrants from high-incidence countries

Background

In low-incidence countries, most tuberculosis (TB) cases occur among migrants and are caused by reactivation of latent tuberculosis infection (LTBI) acquired in the country of origin. Diagnosis and treatment of LTBI are rarely implemented to reduce the burden of TB in immigrants, partly because the cost-effectiveness profile of this intervention is uncertain.

The objective of this research is to perform a review of the literature to assess the cost-effectiveness of LTBI diagnosis and treatment strategies in migrants.

Methods

Scoping review of economic evaluations on LTBI screening strategies for migrants was carried out in Medline.

Results

Nine studies met the inclusion criteria. LTBI screening was cost-effective according to seven studies. Findings of four studies support interferon gamma release assay as the most cost-effective test for LTBI screening in migrants. Two studies found that LTBI screening is cost-effective only if carried out in immigrants who are contacts of active TB cases.

Discussion and Conclusions

Our findings support the cost-effectiveness of LTBI diagnostic and treatment strategies in migrants especially if they are focused on young subjects from high incidence countries. These strategies could represent and adjunctive and synergistic tool to achieve the ambitious aim of TB elimination.

Electronic supplementary material

The online version of this article (doi:10.1186/s12913-015-1045-3) contains supplementary material, which is available to authorized users.

Treating latent TB in primary care: a survey of enablers and barriers among UK General Practitioners

Background

Treating latent tuberculosis infection (LTBI) is an important public health intervention. In the UK, LTBI treatment is delivered in secondary care. Treating LTBI in the community would move care closer to home and could increase uptake and treatment completion rates. However, healthcare providers’ views about the feasibility of this in the UK are unknown. This is the first study to investigate perceived barriers and enablers to primary care-based LTBI treatment among UK general practitioners (GPs).

Methods

A national survey amongst 140 randomly sampled UK GPs practising in areas of high TB incidence was performed. GPs’ experience and perceived confidence, barriers and enablers of primary care-based LTBI treatment were explored and multivariable logistic regression was used to determine whether these were associated with a GP’s willingness to deliver LTBI treatment.

Results

One hundred and twelve (80 %) GPs responded. Ninety-three (83 %; 95 % CI 75 %–89 %) GPs said they would be willing to deliver LTBI treatment in primary care, if key perceived barriers were addressed during service development. The major perceived barriers to delivering primary care-based LTBI treatment were insufficient experience among GPs of screening and treating LTBI, lack of timely specialist support and lack of allied healthcare staff. In addition, GPs felt that appropriate resourcing was key to the successful and sustainable delivery of the service. GPs who reported previous experience of screening or treatment of patients with active or latent TB were almost ten times more likely to be willing to deliver LTBI treatment in primary care compared to GPs with no experience (OR: 9.98; 95 % CI 1.22–81.51).

Conclusions

UK GPs support primary care-based LTBI treatment, provided they are given appropriate training, specialist support, staffing and financing.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-015-1091-9) contains supplementary material, which is available to authorized users.

Gamma Interferon Assays Used in the Diagnosis of Tuberculosis

Tuberculosis (TB) is an ancient disease that has infected humans for thousands of years. However, despite diagnostic tests that detect the disease and effective therapy, there are still millions of people worldwide who are infected with TB. The first TB test used to detect infected patients was a skin test that identifies individuals actively infected with TB. This test used a mix of proteins from culture filtrates of the bacteria Mycobacterium tuberculosis. Recently, two new diagnostic tests have been introduced; these two new tests can detect TB infection in patients by challenging peripheral blood cells with specific TB proteins. These assays measure the cellular immune response to these proteins. This minireview evaluates the new assays and compares them to the use of the TB skin test. The use of these new assays may have some advantages in detecting individuals with active tuberculosis. However, there is still a role for the use of the skin test, especially in young patients.

Optimizing the detection of recent tuberculosis infection in children in a high tuberculosis-HIV burden setting

RATIONALE

Children who are young, malnourished, and infected with HIV have significant risk of tuberculosis (TB) morbidity and mortality following TB infection. Treatment of TB infection is hindered by poor detection and limited pediatric data.

OBJECTIVES

Identify improved testing to detect pediatric TB infection.

METHODS

This was a prospective community-based study assessing use of the tuberculin skin test and IFN-γ release assays among children (n = 1,343; 6 mo to <15 yr) in TB-HIV high-burden settings; associations with child characteristics were measured.

MEASUREMENTS AND MAIN RESULTS

Contact tracing detects TB in 8% of child contacts within 3 months of exposure. Among children with no documented contact, tuberculin skin test and QuantiFERON-TB Gold In-Tube positivity was greater than T-SPOT.TB. Nearly 8% of children had IFN-γ release assay positive and skin test negative discordance. In a model accounting for confounders, all tests correlate with TB contact, but IFN-γ release assays correlate better than the tuberculin skin test (P = 0.0011). Indeterminate IFN-γ release assay results were not associated with age. Indeterminate QuantiFERON-TB Gold In-Tube results were more frequent in children infected with HIV (4.7%) than uninfected with HIV (1.9%), whereas T-SPOT.TB indeterminates were rare (0.2%) and not affected by HIV status. Conversion and reversion were not associated with HIV status. Among children infected with HIV, tests correlated less with contact as malnutrition worsened.

CONCLUSIONS

Where resources allow, use of IFN-γ release assays should be considered in children who are young, recently exposed, and infected with HIV because they may offer advantages compared with the tuberculin skin test for identifying TB infection, and improve targeted, cost-effective delivery of preventive therapy. Affordable tests of infection could dramatically impact global TB control.

Risk factors for latent tuberculosis infection in close contacts of active tuberculosis patients in South Korea: a prospective cohort study

Background

The diagnosis and treatment of latent tuberculosis infection (LTBI) have become mandatory to reduce the burden of tuberculosis worldwide. Close contacts of active TB patients are at high risk of both active and LTBI. The aim of this study is to identify the predominant risk factors of contracting LTBI, persons in close contact with TB patients were recruited. This study also aimed to compare the efficacy of the tuberculin skin test (TST) and QuantiFERON^®-TB GOLD (QFT-G) to diagnose LTBI.

Methods

Close contacts of active pulmonary TB patients visiting a hospital in South Korea were diagnosed for LTBI using TST and/or QFT-G. The association of positive TST and/or QFT-G with the following factors was estimated: age, gender, history of Bacillius Calmette-Guerin (BCG) vaccination, history of pulmonary TB, cohabitation status, the acid-fast bacilli smear status, and presence of cough in source cases.

Results

Of 308 subjects, 38.0% (116/305) were TST positive and 28.6% (59/206) were QFT-G positive. TST positivity was significantly associated with male gender (OR: 1.734; 95% CI: 1.001-3.003, p =0.049), history of pulmonary TB (OR: 4.130; 95% CI: 1.441-11.835, p =0.008) and household contact (OR: 2.130; 95% CI: 1.198-3.786, p =0.01) after adjustment for confounding variables. The degree of concordance between TST and QFT-G was fair (70.4%, κ =0.392).

Conclusions

A prevalence of LTBI among close contacts of active pulmonary TB patients was high, and prior TB history and being a household contact were risk factors of LTBI in the study population.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-014-0566-4) contains supplementary material, which is available to authorized users.

Diagnosis of latent tuberculosis infection before initiation of anti-tumor necrosis factor therapy using both tuberculin skin test and QuantiFERON-TB Gold In Tube assay

BACKGROUND

Reactivation of latent tuberculosis infection (LTBI) is an important complication in patients treated with tumor necrosis factor-alpha (TNF-α) blocking agents. However, the best method for LTBI detection before initiation of anti-TNF therapy remains to be determined.

METHODS

From January 2010 to August 2013, anti-TNF therapy was initiated in 426 patients with immune-mediated inflammatory diseases (IMIDs). Tuberculin skin test (TST) and Quantiferon-TB Gold In Tube (QFT-GIT) assay were performed before starting anti-TNF treatment. LTBI was defined as a positive TST (induration ≥ 10 mm) or as a positive QFT-GIT result. Patients were followed up until December 2013.

RESULTS

The positive TST and QFT-GIT rates were 22.3% (95/426) and 16.0% (68/426), respectively, yielding a total of 27.0% (115/426) of positive LTBI results. LTBI treatment was initiated in 25.1% (107/426) and was completed in 100% (107/107) of patients. During a median 294 days of follow-up, active TB occurred in 1.4% (6/426) of the patients with negative TST and QFT-GIT results at baseline.

CONCLUSION

The either test positive strategy, using both TST and QFT-GIT assay, is acceptable for LTBI screening before commencing anti-TNF therapy in patients with IMIDs.

Pre-placement screening for tuberculosis in healthcare workers

BACKGROUND

Healthcare workers (HCWs) are at occupational risk of contracting and transmitting tuberculosis (TB). Despite national guidance, the optimal process for the pre-placement screening of new entrant HCWs for TB in the UK is not certain, nor the appropriateness of using a one-step interferon gamma release assay (IGRA) screening programme.

AIMS

To assess the potential for an IGRA-only TB screening programme for new entrant HCWs, and identify cost savings achieved through this process.

METHODS

We conducted a retrospective analysis of IGRA and tuberculin skin tests (TST) within our occupational health service over a 3-year period. HCWs with markedly discordant test results (IGRA negative, TST positive) were followed up to determine whether they developed active TB. We also estimated the yearly cost savings if the existing two-step process was replaced with an IGRA-only programme.

RESULTS

Totally, 96/1258 (8%) HCWs had positive IGRA results; 788 TSTs were performed for newly screened IGRA-negative HCWs without Bacille Calmette-Guérin scars, among which 597 (76%) tested negative (TST <6 mm). None of the 10 individuals with grossly discordant test results (TST >15 mm) developed active TB during the study period. We calculated savings of £20,453 if the two-step process was replaced with an IGRA-only programme.

CONCLUSIONS

The absence of disease progression in individuals with markedly discordant results in this study suggest that an IGRA-only screening programme for new HCWs in the UK is feasible, and may be safe although our follow-up period was insufficient. Our results also suggest that substantial cost savings can be made by using this programme.

Prospective head-to-head study comparing 2 commercial interferon gamma release assays for the diagnosis of tuberculous uveitis

PURPOSE

To perform a head-to-head comparison of 2 commercially available interferon-gamma release assays, QuantiFERON-TB Gold In-Tube (Cellestis, Chadstone, Victoria, Australia) and T-SPOT.TB (Oxford Immunotech, Abingdon, Oxfordshire, UK), in the diagnosis of tuberculous uveitis.

DESIGN

Prospective cohort to study diagnostic accuracy.

METHODS

We recruited consecutive new patients who presented with uveitis to a tertiary institution over a 2-year period. All patients underwent complete ocular examination and systemic evaluation, including T-SPOT.TB, QuantiFERON-TB Gold In-Tube, and tuberculin skin test. Patients were followed-up for a minimum of 1 year after completion of antituberculous therapy where indicated. The main outcome measures were the sensitivity, specificity and accuracy of each test, estimated using Bayesian latent class analysis (presented with 95% Bayesian credible intervals) (Crl). Prior information was obtained from published meta-analyses for diagnostic tests: QuantiFERON Gold In-Tube sensitivity (0.64, 0.59-0.69) and specificity (0.99, 0.99-1.00); T-SPOT. tuberculosis sensitivity (0.50, 0.33-0.67) and specificity (0.91, 0.88-0.93).

RESULTS

From our study in patients with uveitis, QuantiFERON-TB Gold In-Tube was more specific but slightly less sensitive (sensitivity: 0.64, 0.60-0.69; specificity: 0.995, 0.988-0.999) than T-SPOT.TB (sensitivity: 0.67, 0.60-0.74; specificity: 0.91, 0.88-0.93). However, QuantiFERON Gold In-Tube was significantly more accurate in identifying true-positive tuberculous uveitis cases than was T-SPOT.TB among discordant cases (QuantiFERON Gold In-Tube positive 98% vs T-SPOT.TB positive 76%; ratio 1.28, 95% Crl: 1.11-1.72, ie, 95% Crl >1.0, statistically significant).

CONCLUSION

Based on statistical decision theory, our head-to-head study suggests that QuantiFERON-TB Gold In-Tube is the first-line test that should be performed in preference to T-SPOT.TB (and the tuberculin skin test) for diagnosing tuberculous uveitis.

Tuberculosis in tropical areas and immigrants

About 95% of cases and 98% of deaths due to tuberculosis (TB) occur in tropical countries while, in temperate low incidence countries, a disproportionate portion of TB cases is diagnosed in immigrants. Urbanization, poverty, poor housing conditions and ventilation, poor nutritional status, low education level, the HIV co-epidemic, the growing impact of chronic conditions such as diabetes are the main determinants of the current TB epidemiology in tropical areas. TB care in these contests is complicated by several barriers such as geographical accessibility, educational, cultural, sociopsychological and gender issues. High quality microbiological and radiological facilities are not widely available, and erratic supply of anti-TB drugs may affect tropical areas from time to time. Nevertheless in recent years, TB control programs reached major achievements in tropical countries as demonstrated by several indicators. Migrants have a high risk of acquire TB before migration. Moreover, after migration, they are exposed to additional risk factors for acquiring or reactivating TB infection, such as poverty, stressful living conditions, social inequalities, overcrowded housing, malnutrition, substance abuse, and limited access to health care. TB mass screening programs for migrants have been implemented in low endemic countries but present several limitations. Screening programs should not represent a stand-alone intervention, but a component of a wider approach integrated with other healthcare activities to ensure the health of migrants.