Interferon Gamma Release Assay versus Tuberculin Skin Testing among Healthcare Workers of Highly Diverse Origin in a Moderate Tuberculosis Burden Country

The risk of tuberculosis infection in Saudi patients receiving adalimumab, etanercept, and tocilizumab therapy

BACKGROUND

The risk of infection including tuberculosis (TB) infection or reactivation during biological therapy with the current various clinical application is a major concern. This risk may be higher in countries endemic to TB. Our aim of this study is to determine the risk of TB infection in patients receiving 3 biological treatments, Adalimumab, Etanercept and Tocilizumab.

METHODS

A retrospective cohort study extending over 2 years follow-up for all patients receiving Adalimumab, Etanercept and Tocilizumab for various clinical indications in a tertiary care center in Saudi Arabia.

RESULT

Over the period of 2015-2019, A total of 410 patients received Adalimumab, 271 received Etanercept and 58 patients received Tocilizumab. Rheumatoid arthritis was the most common indication for therapy in all groups and for Adalimumab the most common indication was inflammatory bowel disease, for Etanercept was psoriatic arthritis and for Tocilizumab was juvenile idiopathic arthritis. After a mean follow up period of 36 ± 8.9 months for patients receiving Adalimumab, 21.5 ± 8.4 months for patients receiving Etanercept and 21 ± 2.5 months for patients receiving Tocilizumab there were no reported cases of TB infection in all groups. Only one patient was diagnosed with latent TB 7 months later after starting Adalimumab and tow patients after starting Etanercept. The overall Interferon Gamma Release Assays (IGRA) positivity rate was 9.7%. There was significant association between IGRA positivity rate and patient age. The cutoff age in which IGRA positivity has significantly increased was 53.20 years.

CONCLUSION

In our study, patients receiving Etanercept, Adalimumab and Tocilizumab had no increased risk of TB infection. Only 0.3% of patients treated with Adalimumab and 0.9% of patients treated with Etanercept converted to a positive IGRA during therapy.

The Risk of Latent Tuberculosis Infection Among Healthcare Workers at a General Hospital in Bisha, the Kingdom of Saudi Arabia

Background and objective Tuberculosis (TB) is a global health issue, often preceded by a latent tuberculosis infection (LTBI) in individuals. Significant global and local efforts have recently been directed toward this infection, focusing on TB control and eradication. This study aimed to assess the magnitude of LTBI among healthcare workers (HCWs) in the Kingdom of Saudi Arabia, by evaluating its prevalence and associated risk factors. Methods An analytical cross-sectional study was conducted among HCWs at the King Abdullah Hospital (KAH), from January to August 2018, by using two surveys: the first one involved data related to HCW demographics and the tuberculin skin test (TST) readings, and the second involved a questionnaire that assessed LTBI risk factors. Results Out of the total 561 HCWs who participated in the study, 66 had an induration reading of more than 10 mm in TST. Many factors were associated with LTBI cases, but multivariate analysis showed that age, gender, and nationality were statistically significant risk factors. Conclusion Given the nature of their work, HCWs are at a greater risk of TB and LTBI. At the same time, HCWs are uniquely positioned to play a crucial role in halting the spread of TB. Gaps in preventive measures may result in the increased spread of TB. Our study assessed risk factors associated with the increased risk of LTBI and proposed possible ways of addressing them.

The Interferon-Gamma Release Assay versus the Tuberculin Skin Test in the Diagnosis of Mycobacterium tuberculosis Infection in BCG-Vaccinated Children and Adolescents Exposed or Not Exposed to Contagious TB

BACKGROUND

Children have an increased risk of developing active tuberculosis (TB) after exposure to Mycobacterium tuberculosis (M.tb), and they are more likely to develop the most severe forms of TB. Rapid diagnosis and treatment of latent M.tb infection (LTBI) is essential to lessen the devastating consequences of TB in children.

OBJECTIVE

The aim of the study was to evaluate TST (tuberculin skin test) and IGRA (interferon-gamma release assay) utility in identifying LTBI in a cohort of Bacille Calmette-Guérin (BCG)-vaccinated Polish children and adolescents exposed or not exposed to contagious TB. In addition, we asked whether quantitative assessment of IGRA results could be valuable in predicting active TB disease.

RESULTS

Of the 235 recruited volunteers, 89 (38%) were TST-positive (TST+), 74 (32%) were IGRA-positive (IGRA+), and 62 (26%) were both TST+ and IGRA+. The frequency of TST positivity was significantly higher in the group with (59%) than without TB contact (18%). The percentage of TST+ subjects increased with age from 36% in the youngest children (<2 years) to 47% in the oldest group (>10 years). All positive IGRA results were found solely in the group of children with TB contact. There was a significant increase in the rate of positive IGRA results with age, from 9% in the youngest to 48% in the oldest group. The 10 mm TST cutoff showed good sensitivity and specificity in both TB exposed and nonexposed children and was associated with excellent negative predictive value, especially among nonexposed volunteers. Mean IFN-γ concentrations in IGRA cultures were significantly higher in the group of LTBI compared to the children with active TB disease, both TST+ and TST-.

CONCLUSIONS

Both TST and IGRA can be used as screening tests for BCG-vaccinated children and adolescents exposed to contagious TB.

Tuberculosis infection status and risk factors among health workers: an updated systematic review

Tuberculosis (TB) infection is a common occupational risk for health workers (HWs) and poses a threat to the patients under their care and to other HWs. Hence, the development of a prevention strategy is crucial. We conducted a study to understand the status and risk factors of TB infection among HWs. The existing literature was searched for all published reports from 1 August 2010 to 31 December 2018, related to TB among HWs according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The inclusion criteria were: (1) study participants working in a health care facility; (2) TB cases diagnosed by medical professionals; (3) original research articles; and (4) English reports in a peer-reviewed journal. We finally included 61 studies from 642 articles searched initially. The TB infection rate in HWs was higher than that of the general population. Based on 39 studies, the prevalence of TB in HWs (tuberculin skin test positive) was 29.94%. In contrast, the global burden of latent TB infection was 23.0% (95% uncertainty interval: 20.4%–26.4%) in 2014. The risk factors of TB among HWs were aging, long duration of employment, nursing professionals, lack of Bacillus Calmette-Guerin vaccination, and low body mass index. HWs have an increased risk for TB infection, which can cause secondary infections in patients or other HWs. An effective prevention strategy must be developed to enable early diagnosis and prompt treatment.

The risk of tuberculosis infection in 410 Saudipatients receiving adalimumab therapy

BACKGROUND

Adalimumab is a fully humanized monoclonal antibody inhibitor of tumor necrosis factor-a used to treat various autoimmune disorders. Adalimumab poses a risk for tuberculosis (TB) infection, especially in countries where TB is endemic.

OBJECTIVE

Determine the rate of TB infection after adalimumab therapy in Saudi Arabia.

DESIGN

Medical record review.

SETTINGS

Tertiary care center in Riyadh.

PATIENTS AND METHODS

Demographic and clinical data were retrieved from the electronic healthcare records of all patients who received adalimumab treatment from 2015 to 2019.

MAIN OUTCOME MEASURES

Occurrence of TB after adalimumab therapy.

SAMPLE SIZE

410 patients (median ([QR] age, 37 [28], range 4-81 years), 40% males RESULTS: Rheumatoid arthritis was the most frequent indication (n=153, 37%). The patients were followed for a mean of 36 (8.9) months. No case of TB infection or reactivation was observed. An inter-feron-gamma release assay (IGRA) was requested in 353/391 (90.3%) patients, prior to initiating therapy. The IGRA was positive in 26 cases (6.6%). The IGRA-positive patients received isoniazid prophylactically. Bacterial infectious complications of adalimumab therapy occurred in 12 (2.9%) patients. Urinary tract infection was the most frequent complication (culture requested in 48 patients, positive in 8).

CONCLUSION

Adalimumab treatment was not associated with a risk of TB disease or TB reactivation in our cohort over the follow-up observation period. No TB reactivation occurred with adalimumab therapy when TB prophylaxis was used. The positive IGRA rate in patients on adalimumab treatment was low (7%).

LIMITATIONS

Single center and one geographical area in Saudi Arabia.

CONFLICT OF INTEREST

None.

Tuberculin Skin Testing versus Interferon-Gamma Release Assay among Users of a Public Health Unit in Northeast Portugal

The screening of groups with a high risk for developing tuberculosis (TB) is a priority in order to control this disease. Since there is no gold standard for the diagnosis of latent TB infection (LTBI), both the tuberculin skin test (TST) and the interferon-gamma release assays (IGRA) have been used for this purpose. The aim of this study was to determine the proportion of LTBI by using the TST and the IGRA tests, and to assess the risk factors related with discordant results between tests across several risk groups advised for screening in Northeast Portugal. Data were collected from the database of patients with suspected LTBI and advised for the screening in a public health unit (January 2014 to December 2015). The proportion of LTBI was computed using both tests. Logistic regression models assessed risk factors for a positive test and for discordant results between tests. The adjusted odds ratio (OR) and respective 95% confidence interval (95% CI) were obtained. Out of 367 patients included in the analysis, 79.8% had a positive TST and 46.0% of them had a positive IGRA. In comparison with contacts of active TB cases, healthcare workers and inmates presented higher odds of TST positivity (OR 4.38, 95% CI 1.59–12.09 and OR 4.74, 95% CI 1.45–15.49, respectively), but immunocompromised people presented lower odds of TST positivity (OR 0.14; 95% CI 0.06–0.31). Instead, healthcare workers (OR 0.44, 95% CI 0.24–0.80) and immunocompromised people (OR 0.24, 95% CI 0.10–0.56) presented lower odds of a positive IGRA. There were 42.0% concordant positive results, 16.1% concordant negative results, and 41.9% discordant results, with healthcare workers presenting higher odds of discordant results (OR 3.34, 95% CI 1.84–6.05). The proportion of LTBI estimated by TST and IGRA among people advised for screening in our setting is high, highlighting the need of preventive strategies. Among healthcare workers, TST results should be read with caution as the higher proportion of discordant results with a positive TST suggests the impact of the booster reaction in this group.

Latent tuberculosis infection among health-care workers using Quantiferon-TB Gold-Plus in a country with a low burden for tuberculosis: prevalence and risk factors

BACKGROUND

Health-care workers (HCW) are susceptible to latent tuberculosis infection (LTBI). The prevalence of LTBI in HCW in Saudi Arabia has not been reported using the fourth-generation interferon gamma release assay QuantiFERON-TB Gold Plus (QFT-Plus).

OBJECTIVE

Determine the prevalence of LTBI in a large heterogeneous HCW population and assess risk factors for LTBI.

DESIGN

Cross-sectional and case-control study.

SETTING

Tertiary academic hospital, Riyadh, Saudi Arabia.

PATIENTS AND METHODS

Medical records of HCWs who had QFT-Plus performed between January to December 2018 were reviewed and included in the cross-sectional study. In a subset analysis, randomly selected positive QFT-Plus cases were compared with controls selected from the same areas of work. Univariate and binary logistic regression analyses were performed to assess the significance of other factors to QFT-PLus positivity.

MAIN OUTCOME MEASURES

Prevalence of LTBI in HCWs and potential risk factors for LTBI.

SAMPLE SIZE

3024 HCWs in the cross-sectional analysis; 294 cases and 294 controls in the case-control analysis.

RESULTS

Twenty-four percent (n=733) of the HCWs had a positive QFT-Plus. The median (interquartile range) age was 34.0 (31.0-37.1) years, 71% were female, and only 24.8% were of Saudi nationals. Nursing represented 57.7% of HCWs, and 24.7% were working in a non-clinical area. Only 20.3% worked in TB-related departments. A higher risk of LTBI was present in HCWs who were older than 50 years (OR=1.95), from either Philippines (OR=4.7) or the Indian subcontinent (OR=4.1), working as a nurse (OR=2.7), allied health profession (OR=2.1), radiology technician (OR=3.1), or in the emergency room (OR=2.4) or intensive care unit (OR=2.1). In the binary logistic regression, independent predictors for positive QFT-Plus were age group older than 50 years (aOR=2.96), known TB exposure (aOR=1.97), and not receiving BCG at birth (aOR=3.08).

LIMITATION

Single-center, retrospective, possible recall bias for BCG vaccination.

CONCLUSION

The high prevalence of LTBI among HCW emphasizes the need to continue pre-employment screening, especially for employed personnel from high endemic areas, with targeted annual screening for the same group and other identified high-risk groups. These findings can aid in the development of national screening guidelines for LTBI in HCW.

CONFLICT OF INTEREST

None.

Isolation measures and protection awareness are significant for latent tuberculosis infection: a cross-sectional study based on T-SPOT.TB among health care workers in China

This study aimed to reveal the associated risk factors for latent tuberculosis infection (LTBI) detected by T-SPOT.TB assay among health care workers (HCWs) at different working locations or job categories in China. This cross-sectional study included 934 HCWs who underwent the T-SPOT.TB assay. Demographic and social characteristics of the participants, including age, sex, job categories, department/ward and duration of healthcare service, were recorded. Among 934 HCWs, 267 (28.5867%) were diagnosed as having LTBI with positive T-SPOT.TB assay. HCWs working in inpatient tuberculosis (TB) (odds ratio (OR) 2.917; 95% confidence interval (CI) 1.852–4.596; P < 0.001) and respiratory wards (OR 1.840; 95% CI 1.124–3.011; P = 0.015), and with longer duration of healthcare service (OR 1.048; 95% CI 1.016–1.080; P = 0.003) were risk factors for positive T-SPOT.TB result. Furthermore, longer working duration increased the positive rate of T-SPOT.TB results for physicians and nurses, and physicians had higher risks than nurses for the same working duration. Inpatient TB and respiratory wards were high-risk working locations for HCWs with LTBI, and longer duration of healthcare service also increased the risk of LTBI among HCWs. A complete strategy for TB infection control and protection awareness among HCWs should be enhanced.

Undiagnosed diabetes mellitus and tuberculosis infection: A population-based, observational study from eastern China

BACKGROUND

China has the largest dual diabetes and tuberculosis epidemic globally. No studies from mainland China have assessed the relationship between tuberculosis infection and diabetes. We conducted a population-based, observational study in eastern China to further explore this relationship.

METHODS

A blood glucose, Quantiferon, and tuberculin skin test were administered at baseline. We compared tuberculosis infection in nondiabetics and diabetics. The cohort was additionally screened for tuberculosis progression over 5 years.

RESULTS

Among 5405 participants, diabetics had elevated levels of Quantiferon and tuberculin positivity, largely driven by undiagnosed diabetics (compared with nondiabetics, adjusted odds ratios of 1.53; 95% confidence interval [CI], 1.05-2.23 and 1.58; 95% CI, 1.07-2.35 for tuberculin and Quantiferon positivity). During follow-up, the annual tuberculosis incidence was three times higher for diabetics compared with the entire cohort.

CONCLUSIONS

These results suggest improving diabetic control through rapidly identifying undiagnosed diabetes may have indirect benefits to tuberculosis control. Targeting of preventive therapy to newly diagnosed diabetics at high-risk for progressive tuberculosis in China should be considered.

Risk of Occupational Latent Tuberculosis Infection among Health Personnel Measured by Interferon-Gamma Release Assays in Low Incidence Countries-A Systematic Review and Meta-Analysis

Healthcare workers (HCWs) have increased risk for latent tuberculosis infection (LTBI) and tuberculosis (TB) disease due to their occupational exposure. For some years now, interferon-γ release assays (IGRAs) have replaced the tuberculin skin test for the diagnosis of LTBI in many countries. This review examined the occupational risk of LTBI in HCWs with IGRA testing in low incidence countries. A systematic review and meta-analysis of studies from 2005 onwards provide data regarding the prevalence of LTBI in HCWs. In addition, the pooled effect estimates were calculated for individual regions and occupational groups. 57 studies with 31,431 HCWs from four regions and a total of 25 countries were analysed. The prevalence of LTBI varied from 0.9 to 85.5%. The pooled estimation found the lowest prevalence of LTBI for North American and West Pacific countries (<5%), and the highest prevalence for Eastern Mediterranean countries (19.4%). An increased risk for LTBI was found only for administrative employees. Studies on the occupational risk of LTBI continue to show increased prevalence of HCWs, even in low-incidence countries. Good quality studies will continue to be needed to describe occupational exposure.

Prevalence of latent tuberculosis infection in healthcare workers in tertiary care hospitals of Pakistan

Objective

To determine the prevalence of latent tuberculosis infection (LTBI) in healthcare workers in tertiary care hospitals of Rawalpindi, using interferon gamma release assay.

Methods

It was a cross-sectional study. The samples were collected from pulmonology and microbiology departments of three hospitals; i) Military Hospital, Rawalpindi, ii) Fauji Foundation Hospital, Rawalpindi and iii) Pakistan Institute of Medical Sciences, Islamabad. The study was completed in one year from January 2017 to January 2018. Fifty-five asymptomatic healthcare workers of both genders between the ages of 18-50 years with a working tenure of at least one year in concerned departments were included and those with active tuberculosis were excluded from the study. Whole blood from subjects was collected and plasma was checked for interferon gamma value by IGRA (Interferon gamma release assay).

Results

In this study of total 55 healthcare workers a high prevalence 22 (40.0%) of latent tuberculosis was found. When LTBI distribution was analyzed within occupational categories, the most frequently affected were sanitary workers 3 (100.0%), nurses 5 (50.0%), doctors 6 (43%) and nursing assistants 2 (40%).

Conclusion

The prevalence of LTBI in healthcare workers is alarmingly high in our local healthcare settings.

Expression of USP18 and IL2RA Is Increased in Individuals Receiving Latent Tuberculosis Treatment with Isoniazid

BACKGROUND

The treatment of latent tuberculosis infection (LTBI) in individuals at risk of reactivation is essential for tuberculosis control. However, blood biomarkers associated with LTBI treatment have not been identified.

METHODS

Blood samples from tuberculin skin test (TST) reactive individuals were collected before and after one and six months of isoniazid (INH) therapy. Peripheral mononuclear cells (PBMC) were isolated, and an in-house interferon-γ release assay (IGRA) was performed. Expression of chemokine ligand 4 (CCL4), chemokine ligand 10 (CXCL10), chemokine ligand 11 (CXCL11), interferon alpha (IFNA), radical S-adenosyl methionine domain-containing 2 (RSAD2), ubiquitin-specific peptidase 18 (USP18), interferon-induced protein 44 (IFI44), interferon-induced protein 44 like (IFI44L), interferon-induced protein tetratricopeptide repeats 1(IFIT1), and interleukin 2 receptor subunit alpha (IL2RA) mRNA levels were assessed by qPCR before, during, and after INH treatment.

RESULTS

We observed significantly lower relative abundances of USP18, IFI44L, IFNA, and IL2RA transcripts in PBMC from IGRA-positive individuals compared to levels in IGRA-negative individuals before INH therapy. Also, relative abundance of CXCL11 was significantly lower in IGRA-positive than in IGRA-negative individuals before and after one month of INH therapy. However, the relative abundance of CCL4, CXCL10, and CXCL11 mRNA was significantly decreased and that of IL2RA and USP18 significantly increased after INH therapy, regardless of the IGRA result. Our results show that USP18, IFI44L, IFIT1, and IL2RA relative abundances increased significantly, meanwhile the relative abundance of CCL4, CXCL11, and IFNA decreased significantly after six months of INH therapy in TST-positive individuals.

CONCLUSIONS

Changes in the profiles of USP18, IL2RA, IFNA, CCL4, and CXCL11 expressions during INH treatment in TST-positive individuals, regardless of IGRA status, are potential tools for monitoring latent tuberculosis treatment.

Infection free "resisters" among household contacts of adult pulmonary tuberculosis

Despite substantial exposure to infectious pulmonary tuberculosis (TB) cases, some household contacts (HHC) never acquire latent TB infection (LTBI). Characterizing these “resisters” can inform who to study immunologically for the development of TB vaccines. We enrolled HHCs of culture-confirmed adult pulmonary TB in India who underwent LTBI testing using tuberculin skin test (TST) and QuantiFERON TB Gold Test-in-tube (QFT-GIT) at baseline and, if negative by both (<5mm TST and <0.35IU/mL QFT-GIT), underwent follow-up testing at 4–6 and/or 12 months. We defined persons with persistently negative LTBI tests at both baseline and followup as pLTBI- and resisters as those who had a high exposure to TB using a published score and remained pLTBI-. We calculated the proportion of resisters overall and resisters with complete absence of response to LTBI tests (0mm TST and/or QFT-GIT <0.01 IU/ml). Using random effects Poisson regression, we assessed factors associated with pLTBI-. Of 799 HHCs in 355 households, 67 (8%) were pLTBI- at 12 months; 52 (6.5%) pLTBI- in 39 households were resisters. Complete absence of response to LTBI tests was found in 27 (53%) resisters. No epidemiological characteristics were associated with the pLTBI- phenotype. LTBI free resisters among HHC exist but are uncommon and are without distinguishing epidemiologic characteristics. Assessing the genetic and immunologic features of such resister individuals is likely to elucidate mechanisms of protective immunity to TB.

Screening of healthcare workers for latent tuberculosis infection in the low tuberculosis burden country: QuantiFERON-TB gold in tube test or tuberculin skin test?

Healthcare workers (HCWs) are an important group at increased risk for exposure to various infectious agents including Mycobacterium tuberculosis. Unfortunately, there is very limited data on the prevalence of latent tuberculosis infection (LTBI) among HCWs in Iran. The aim of this study was to analyze the prevalence of LTBI among HCW's of Children Medical Center (CMC), an Iranian referral hospital, and to compare the feasibility of using tuberculin skin test (TST) and QuantiFERON-TB gold in tube test (QFT-GIT) to screen the LTBI among this population. Informed consent was obtained before the study questionnaire was completed. Participants were then evaluated for LTBI using QFT-GIT test followed immediately by TST. The prevalence of latent TB infection in the 101 HCWs, based on QFT-GIT positivity, was 47% (n = 47), while based on TST test a higher prevalence was observed (n = 57, 57%). Forty-five (45%) subjects were positive for both tests, whereas 14 (14%) were positive by either test. Among the TST positive cases, 21% (n = 12) were negative for QFT-GIT. The overall agreement of TST and QFT-GIT was 86% ([45 + 42]/101] and a moderate correlation between these two tests was observed (Kappa value 0.72). The use of QFT-GIT test as a second step in TST-positive cases offers an appropriate tool for LTBI detection in our country where all HCWs are BCG-vaccinated. To enable the effective control and prevention of TB in healthcare settings in Iran, specific and detailed guidelines for dealing with LTBI are highly required. All newly hired HCWs should receive baseline testing for LTBI before commencing employment. In addition, HCWs who work in high-risk departments should receive regular follow-up screening for LTBI.

Screening of latent tuberculosis infection among health care workers working in Hajj pilgrimage area in Saudi Arabia, using interferon gamma release assay and tuberculin skin test

BACKGROUND

Interferon gamma release assays (IGRA) is highly specific for Mycobacterium tuberculosis and is the preferred test in BCG-vaccinated individuals. The few studies that have screened health care workers (HCWs) in Saudi Arabia for latent tuberculosis infection (LTBI) using IGRA have varied in agreement with the traditional tuberculin skin test (TST).

OBJECTIVE

Assess the prevalence of LTBI among HCWs working in the Hajj pilgrimage using IGRA and TST and measuring their agreement.

DESIGN

Cross-sectional prospective.

SETTING

Multiple non-tertiary care hospitals.

PATIENTS AND METHODS

HCWs who worked during the Hajj pilgrimage in Saudi Arabia in December 2015. Data was collected by standarized questionnaire. Samples were drawn and analyzed by standard methods.

MAIN OUTCOME MEASURES

The prevalence of LTBI among HCW and the agreement by kappa statistic between QFT-GIT and TST.

SAMPLE SIZE

520 subjects.

RESULTS

Nurses accounted for 30.7% of the sample and physicians, 19.2%. The majority were BCG vaccinated (98.5%). There were a total of 56 positive by QFT-GIT and the LTBI rate was 10.8%. In 50 QFT positive/476 TST negative the LTBI rate was 10.5% in discordant tests, and in 6 QFT positive/44 TST positive it was 13.6% in concordant tests. The overall agreement between both tests was poor-83% and kappa was 0.02. LTBI prevalence was associated with longer employment (13.1 [9.2] years). The QFT-GIT positive test was significantly higher in physicians (P=.02) and in HCWs working in chest hospitals 16/76 (21.05%) (P=.001).

CONCLUSION

Agreement between the tests was poor. QFT-GIT detected LTBI when TST was negative in HCWs who had a history of close contact with TB patients.

LIMITATIONS

A second step TST was not feasible within 2-3 weeks.

CONFLICT OF INTEREST

None.

Interferon-gamma release assay for the diagnosis of latent tuberculosis infection: A latent-class analysis

BACKGROUND

Accurate diagnosis and subsequent treatment of latent tuberculosis infection (LTBI) is essential for TB elimination. However, the absence of a gold standard test for diagnosing LTBI makes assessment of the true prevalence of LTBI and the accuracy of diagnostic tests challenging. Bayesian latent class models can be used to make inferences about disease prevalence and the sensitivity and specificity of diagnostic tests using data on the concordance between tests. We performed the largest meta-analysis to date aiming to evaluate the performance of tuberculin skin test (TST) and interferon-gamma release assays (IGRAs) for LTBI diagnosis in various patient populations using Bayesian latent class modelling.

METHODS

Systematic search of PubMeb, Embase and African Index Medicus was conducted without date and language restrictions on September 11, 2017 to identify studies that compared the performance of TST and IGRAs for LTBI diagnosis. Two IGRA methods were considered: QuantiFERON-TB Gold In Tube (QFT-GIT) and T-SPOT.TB. Studies were included if they reported 2x2 agreement data between TST and QFT-GIT or T-SPOT.TB. A Bayesian latent class model was developed to estimate the sensitivity and specificity of TST and IGRAs in various populations, including immune-competent adults, immune-compromised adults and children. A TST cut-off value of 10 mm was used for immune-competent subjects and 5 mm for immune-compromised individuals.

FINDINGS

A total of 157 studies were included in the analysis. In immune-competent adults, the sensitivity of TST and QFT-GIT were estimated to be 84% (95% credible interval [CrI] 82-85%) and 52% (50-53%), respectively. The specificity of QFT-GIT was 97% (96-97%) in non-BCG-vaccinated and 93% (92-94%) in BCG-vaccinated immune-competent adults. The estimated figures for TST were 100% (99-100%) and 79% (76-82%), respectively. T-SPOT.TB has comparable specificity (97% for both tests) and better sensitivity (68% versus 52%) than QFT-GIT in immune-competent adults. In immune-compromised adults, both TST and QFT-GIT display low sensitivity but high specificity. QFT-GIT and TST are equally specific (98% for both tests) in non-BCG-vaccinated children; however, QFT-GIT is more specific than TST (98% versus 82%) in BCG-vaccinated group. TST is more sensitive than QFT-GIT (82% versus 73%) in children.

CONCLUSIONS

This study is the first to assess the utility of TST and IGRAs for LTBI diagnosis in different population groups using all available data with Bayesian latent class modelling. Our results challenge the current beliefs about the performance of LTBI screening tests, and have important implications for LTBI screening policy and practice. We estimated that the performance of IGRAs is not as reliable as previously measured in the general population. However, IGRAs are not or minimally affected by BCG and should be the preferred tests in this setting. Adoption of IGRAs in settings where BCG is widely administered will allow for a more accurate identification and treatment of LTBI.

Evaluation of Tuberculin Skin Test Positivity and Early Tuberculin Conversion among Medical Intern Trainees in Tunisia

BACKGROUND

As healthcare workers (HCWs), medical trainees are at a high-risk for acquisition of tuberculosis (TB) infection and disease. To our knowledge, there are no published data about TB infection among medical trainees in Tunisia.To determine the tuberculin skin test (TST) positivity and tuberculin conversion among a group of medical trainees in different departments at our institution.

MATERIALS AND METHODS

We performed a prospective study using the TST. The study was conducted in two steps: 1) an initial TST survey and 2) an evaluation of the TST conversion rates.

RESULTS

Among 114 participants, the TST was positive (≥10 mm) in 26.3% and negative (<5 mm) in 57%. The conversion rate of TST was 4%, which was only observed among the trainees assigned to the pulmonary departments. The significant predictor variables of TST positivity were a history of nosocomial TB exposure and training in a high-risk area.

CONCLUSION

Despite the small number of participants, the high TB conversion rate among the trainees is alarming. This population represents an important target group for a latent tuberculosis infection screening program in countries with limited resources such as Tunisia.

Highly Multiplexed Proteomic Analysis of Quantiferon Supernatants To Identify Biomarkers of Latent Tuberculosis Infection

The tests for diagnosing latent tuberculosis infection (LTBI) are limited by a poor predictive value for identifying people at the highest risk for progressing to active tuberculosis (TB) and have various sensitivities and specificities in different populations. Identifying a more robust signature for LTBI is important for TB prevention and elimination. A pilot study was conducted with samples from immigrants to the United States that were screened for LTBI by the three commercially approved tests, namely, the tuberculin skin test (TST), the Quantiferon-TB Gold in-tube (QFT-GIT), and the T-SPOT.TB (T-SPOT). QFT-GIT supernatants from 13 people with concordant positive results and 26 people with concordant negative results were analyzed via the highly multiplexed SOMAscan proteomic assay. The proteins in the stimulated supernatants that distinguished LTBI from controls included interleukin-2 (IL-2), monocyte chemotactic protein 2 (MCP-2), interferon gamma inducible protein-10 (IP-10), interferon gamma (IFN-γ), tumor necrosis factor superfamily member 14 (TNFSF14, also known as LIGHT), monokine induced by gamma interferon (MIG), and granzyme B (P <0.00001). In addition, antigen stimulation increased the expression of heparin-binding EGF-like growth factor (HB-EGF) and activin AB in LTBI samples. In nil tubes, LIGHT was the most significant marker (P <0.0001) and was elevated in LTBI subjects. Other prominent markers in nonstimulated QFT-GIT supernatants were the complement-3 components C3b, iC3b, and C3d, which were upregulated in LTBI and markedly decreased upon stimulation. We found known and novel proteins that warrant further studies for developing improved tests for LTBI, for predicting progression to active disease, and for discriminating LTBI from active TB.