Risk-benefit analysis of tuberculosis infection testing for household contact management in high-burden countries: a mathematical modelling study

Tuberculosis Immunoreactivity Surveillance in Malawi (Timasamala)-A protocol for a cross-sectional Mycobacterium tuberculosis immunoreactivity survey in Blantyre, Malawi

Tuberculosis (TB) transmission and prevalence are dynamic over time, and heterogeneous within populations. Public health programmes therefore require up-to-date, accurate epidemiological data to appropriately allocate resources, target interventions, and track progress towards End TB goals. Current methods of TB surveillance often rely on case notifications, which are biased by access to healthcare, and TB disease prevalence surveys, which are highly resource-intensive, requiring many tens of thousands of people to be tested to identify high-risk groups or capture trends. Surveys of "latent TB infection", or immunoreactivity to Mycobacterium tuberculosis (Mtb), using tests such as interferon-gamma release assays (IGRAs) could provide a way to identify TB transmission hotspots, supplementing information from disease notifications, and with greater spatial and temporal resolution than is possible to achieve in disease prevalence surveys. This cross-sectional survey will investigate the prevalence of Mtb immunoreactivity amongst young children, adolescents and adults in Blantyre, Malawi, a high HIV-prevalence city in southern Africa. Through this study we will estimate the annual risk of TB infection (ARTI) in Blantyre and explore individual- and area-level risk factors for infection, as well as investigating geospatial heterogeneity of Mtb infection (and its determinants), and comparing these to the distribution of TB disease case-notifications. We will also evaluate novel diagnostics for Mtb infection (QIAreach QFT) and sampling methodologies (convenience sampling in healthcare settings and community sampling based on satellite imagery), which may increase the feasibility of measuring Mtb infection at large scale. The overall aim is to provide high-resolution epidemiological data and provide new insights into methodologies which may be used by TB programmes globally.

Effectiveness of preventive treatment among different age groups and Mycobacterium tuberculosis infection status: a systematic review and individual-participant data meta-analysis of contact tracing studies

BACKGROUND

Tuberculosis is a preventable disease. However, there is debate regarding which individuals would benefit most from tuberculosis preventive treatment and whether these benefits vary in settings with a high burden and low burden of tuberculosis. We aimed to compare the effectiveness of tuberculosis preventive treatment in exposed individuals of differing ages and Mycobacterium tuberculosis infection status while considering tuberculosis burden of the settings.

METHODS

In this systematic review and individual-participant meta-analysis, we investigated the development of incident tuberculosis in people closely exposed to individuals with tuberculosis. We searched for studies published between Jan 1, 1998, and April 6, 2018, in MEDLINE, Web of Science, BIOSIS, and Embase. We restricted our search to cohort studies; case-control studies and outbreak reports were excluded. Two reviewers evaluated titles, abstracts, and full text articles for eligibility. At each stage, two reviewers discussed discrepancies and re-evaluated articles until a consensus was reached. Individual-participant data and a pre-specified list of variables, including characteristics of the exposed contact, the index patient, and environmental characteristics, were requested from authors of all eligible studies; contacts exposed to a drug-resistant tuberculosis index patient were excluded. The primary study outcome was incident tuberculosis. We estimated adjusted hazard ratios (aHRs) for incident tuberculosis with mixed-effects Cox regression models with a study-level random effect. We estimated the number-needed-to-treat (NNT) to prevent one person developing tuberculosis. Propensity score matching procedures were used in all analyses. This study is registered with PROSPERO (CRD42018087022).

FINDINGS

After screening 25 358 records for eligibility, 439 644 participants from 32 cohort studies were included in the individual-participant data meta-analysis. Participants were followed for 1 396 413 person-years (median of 2·7 years [IQR 1·3-4.4]), during which 2496 people were diagnosed with incident tuberculosis. Overall, effectiveness of preventive treatment was 49% (aHR 0·51 [95% CI 0·44-0·60]). Participants with a positive tuberculin-skin-test (TST) or IFNγ release assay (IGRA) result at baseline benefitted from greater protection, regardless of age (0·09 [0·05-0·17] in children younger than 5 years, 0·20 [0·15-0·28] in individuals aged 5-17 years, and 0·17 [0·13-0·22] in adults aged 18 years and older). The effectiveness of preventive treatment was greater in high-burden (0·31 [0·23-0·40]) versus low-burden (0·58 [0·47-0·72]) settings. The NNT ranged from 9 to 34 depending on age among participants with a positive TST or IGRA in both high-burden and low-burden settings; among all contacts (regardless of TST or IGRA test result), the NNT ranged from 29 to 43 in high-burden settings and 213 to 455 in low-burden settings.

INTERPRETATION

Our findings suggest that a risk-targeted strategy prioritising contacts with evidence of M tuberculosis infection might be indicated in low-burden settings, and a broad approach including all contacts should be considered in high-burden settings. Preventive treatment was similarly effective among contacts of all ages.

FUNDING

None.

Impact and cost-effectiveness of short-course tuberculosis preventive treatment for household contacts and people with HIV in 29 high-incidence countries: a modelling analysis

BACKGROUND

Guidelines and implementation of tuberculosis preventive treatment (TPT) vary by age and HIV status. Specifically, TPT is strongly recommended for people living with HIV/AIDS (PLWHA) and household contacts younger than 5 years but only conditionally recommended for older contacts. Cost remains a major barrier to implementation. The aim of this study was to evaluate the cost-effectiveness of TPT for household contacts and PLWHA.

METHODS

We developed a state-transition model to simulate short-course TPT for household contacts and PLWHA in 29 high-incidence countries based on data from previous studies and public databases. Our primary outcome was the incremental cost-effectiveness ratio, expressed as incremental discounted costs (2020 US$, including contact investigation costs) per incremental discounted disability-adjusted life year (DALY) averted, compared with a scenario without any TPT or contact investigation. We propagated uncertainty in all model parameters using probabilistic sensitivity analysis and also evaluated the sensitivity of results to the screening algorithm used to rule out active disease, the choice of TPT regimen, the modelling time horizon, assumptions about TPT coverage, antiretroviral therapy discontinuation, and secondary transmission.

FINDINGS

Between 2023 and 2035, scaling up TPT prevented 0·9 (95% uncertainty interval 0·4-1·6) people from developing tuberculosis and 0·13 (0·05-0·27) tuberculosis deaths per 100 PLWHA, at an incremental cost of $15 (9-21) per PLWHA. For household contacts, TPT (with contact investigation) averted 1·1 (0·5-2·0) cases and 0·7 (0·4-1·0) deaths per 100 contacts, at a cost of $21 (17-25) per contact. Cost-effectiveness was most favourable for household contacts younger than 5 years ($22 per DALY averted) and contacts aged 5-14 years ($104 per DALY averted) but also fell within conservative cost-effectiveness thresholds in many countries for PLWHA ($722 per DALY averted) and adult contacts ($309 per DALY averted). Costs per DALY averted tended to be lower when compared with a scenario with contact investigation but no TPT. The cost-effectiveness of TPT was not substantially altered in sensitivity analyses, except that TPT was more favourable in analysis that considered a longer time horizon or included secondary transmission benefits.

INTERPRETATION

In many high-incidence countries, short-course TPT is likely to be cost-effective for PLWHA and household contacts of all ages, regardless of whether contact investigation is already in place. Failing to implement tuberculosis contact investigation and TPT will incur a large burden of avertable illness and mortality in the next decade.

FUNDING

Unitaid.

Community-based tuberculosis contact management: Caregiver experience and factors promoting adherence to preventive therapy

Delivery of tuberculosis preventive therapy (TPT) for children with household exposure to tuberculosis is a globally supported intervention to reduce the impact of tuberculosis disease (TB) in vulnerable children; however, it is sub-optimally implemented in most high-burden settings. As part of a community-based household contact management program, we evaluated predictors of adherence to community based TPT in children and performed qualitative assessments of caregiver experiences. The Vikela Ekhaya (Protect the Home) project was a community-based household contact management program implemented between 2019 and 2020 in the Hhohho Region of Eswatini. At home visits, contact management teams screened children for TB, initiated TPT when indicated and performed follow-up assessments reviewing TPT adherence. TPT non-adherence was defined as either two self-reported missed doses or a pill count indicating at least two missed doses, and risk factors were evaluated using multivariate clustered Cox regression models. Semi-structured interviews were performed with caregivers to assess acceptability of home visits for TPT administration. In total, 278 children under 15 years initiated TPT and 96% completed TPT through the Vikela Ekhaya project. Risk factors for TPT non-adherence among children initiating 3HR included low family income (adjusted hazard ratio (aHR) 2.3, 95%CI 1.2-4.4), female gender of the child (aHR 2.5, 95% CI 1.4-5.0) and an urban living environment (aHR 3.1, 95%CI 1.6-6.0). Children with non-adherence at the first follow-up visit were 9.1 fold more likely not to complete therapy. Caregivers indicated an appreciation for community services, citing increased comfort, reduced cost, and support from community members. Our results are supportive of recent World Health Organization (WHO) recommendations for decentralization of TB preventive services. Here, we identify populations that may benefit from additional support to promote TPT adherence, but overall demonstrate a clear preference for and excellent outcomes with community based TPT delivery.

Effect of pregnancy versus postpartum maternal isoniazid preventive therapy on infant growth in HIV-exposed uninfected infants: a post-hoc analysis of the TB APPRISE trial

Background

Isoniazid preventive therapy (IPT) initiation during pregnancy was associated with increased incidence of adverse pregnancy outcomes in the TB APPRISE trial. Effects of in utero IPT exposure on infant growth are unknown.

Methods

This post-hoc analysis used data from the TB APPRISE trial, a multicentre, double-blind, placebo-controlled trial, which randomised women to 28-week IPT starting in pregnancy (pregnancy-IPT) or postpartum week 12 (postpartum-IPT) in eight countries with high tuberculosis prevalence. Participants were enrolled between August 2014 and April 2016. Based on modified intent-to-treat analyses, we analysed only live-born babies who had at least one follow-up after birth and compared time to infant growth faltering between arms to 12 weeks and 48 weeks postpartum in overall and sex-stratified multivariable Cox proportional hazards regression. Factors adjusted in the final models include sex of infant, mother's baseline BMI, age in years, ART regimen, viral load, CD4 count, education, and household food insecurity.

Results

Among 898 HIV-exposed uninfected (HEU) infants, 447 (49.8%) were females. Infants in pregnancy-IPT had a 1.47-fold higher risk of becoming underweight by 12 weeks (aHR 1.47 [95% CI: 1.06, 2.03]) than infants in the postpartum-IPT; increased risk persisted to 48 weeks postpartum (aHR 1.34 [95% CI: 1.01, 1.78]). Maternal IPT timing was not associated with stunting or wasting. In sex-stratified analyses, male infants in the pregnancy-IPT arm experienced an increased risk of low birth weight (LBW) (aRR 2.04 [95% CI: 1.16, 3.68), preterm birth (aRR 1.81 [95% CI: 1.04, 3.21]) and becoming underweight by 12 weeks (aHR 2.02 [95% CI: 1.29, 3.18]) and 48 weeks (aHR 1.82 [95% CI: 1.23, 2.69]). Maternal IPT timing did not influence growth in female infants.

Interpretation

Maternal IPT during pregnancy was associated with an increased risk of LBW, preterm birth, and becoming underweight among HEU infants, particularly male infants. These data add to prior TB APPRISE data, suggesting that IPT during pregnancy impacts infant growth, which could inform management, and warrants further examination of mechanisms.

Funding

The TB APPRISE study Supported by the National Institutes of Health (NIH) (award numbers, UM1AI068632 [IMPAACT LOC], UM1AI068616 [IMPAACT SDMC], and UM1AI106716 [IMPAACT LC]) through the National Institute of Allergy and Infectious Diseases, with cofunding from the Eunice Kennedy Shriver National Institute of Child Health and Human Development (contract number, HHSN275201800001I) and the National Institute of Mental Health.

Testing and Scaling Interventions to Improve the Tuberculosis Infection Care Cascade

Tuberculosis (TB) preventive therapy (TPT) is increasingly recognized as the key to eliminating tuberculosis globally and is particularly critical for children with TB infection or who are in close contact with individuals with infectious TB. But many barriers currently impede successful scale-up to provide TPT to those at high risk of TB disease. The cascade of care in TB infection (and the related contact management cascade) is a conceptual framework to evaluate and improve the care of persons who are potential candidates for TPT. This review summarizes recent literature on barriers and solutions in the TB infection care cascade, focusing on children in both high- and low-burden settings, and drawing from studies on children and adults. Identifying and closing gaps in the care cascade will require the implementation of tools that are new (e.g. computer-assisted radiography) and old (e.g. efficient contact tracing), and will be aided by innovative implementation study designs, quality improvement methods, and shared clinical practice with primary care providers.

Latent Tuberculosis Cascade of Care Among Healthcare Workers: A Nationwide Cohort Analysis in Korea Between 2017 and 2018

BACKGROUND

In 2017, Korea implemented nationwide latent tuberculosis infection (LTBI) project targeting healthcare workers (HCWs). We aimed to assess its performance using the cascade of care model.

METHODS

We included 45,503 employees of medical institutions with positive interferon-gamma release assay result who participated between March 2017 and December 2018. We described percentages of LTBI participants completing each step in the cascade of care. Poisson regression model was conducted to assess individual characteristics and factors associated with not-visiting clinics for further care, not-initiating LTBI treatment, and not-completing treatment.

RESULTS

Proportions of visiting clinics and initiating and completing treatment in HCWs were 54.9%, 38.5%, and 32.0%, respectively. Despite of less likelihood of visiting clinics and initiating LTBI treatment, older age ≥ 65 years were more likely to complete treatment (adjusted relative risk [aRR], 0.80; 95% confidence interval [CI], 0.64-0.99), compared to young age < 35 years. Compared to nurses, doctors were less likely to visit clinic; however, were more likely to initiate treatment (aRR, 0.88; 95% CI, 0.81-0.96). Those who visited public health centers were associated with not-initiating treatment (aRR, 1.34; 95% CI, 1.29-1.40). When treated at private hospitals, 9-month isoniazid monotherapy was less likely to complete treatment, compared to 3-month isoniazid and rifampicin combination therapy (aRR, 1.33; 95% CI, 1.16-1.53).

CONCLUSION

Among employees of medical institutions with LTBI, only one third completed treatment. Age, occupation, treatment center, and initial regimen were significantly related to LTBI treatment performance indicators. Rifampicin-based short treatment regimens were effective under standard of care.

Provision of Decentralized TB Care Services: A Detect-Treat-Prevent Strategy for Children and Adolescents Affected by TB

In this review, we discuss considerations and successful models for providing decentralized diagnosis, treatment, and prevention services for children and adolescents. Key approaches to building decentralized capacity for childhood TB diagnosis in primary care facilities include provider training and increased access to child-focused diagnostic tools and techniques. Treatment of TB disease should be managed close to where patients live; pediatric formulations of both first- and second-line drugs should be widely available; and any hospitalization should be for as brief a period as medically indicated. TB preventive treatment for child and adolescent contacts must be greatly expanded, which will require home visits to identify contacts, building capacity to rule out TB, and adoption of shorter preventive regimens. Decentralization of TB services should involve the private sector, with collaborations outside the TB program in order to reach children and adolescents where they first enter the health care system. The impact of decentralization will be maximized if programs are family-centered and designed around responding to the needs of children and adolescents affected by TB, as well as their families.

The paradigm shift in the approach to management of latent tuberculosis infection in high tuberculosis burden countries

Introduction: Addressing the reservoir of Latent Tuberculosis Infection (LTBI) is critical to TB elimination because if left untreated LTBI can progress to active TB disease. This additional burden can prevent achieving the global targets of TB elimination. Management of LTBI has been a low priority target for National TB Elimination Programs (NTEP) due to various challenges in the field settings.Areas covered: This article reviews the most recent advances in the field of LTBI management including newer diagnostics, treatments, vaccines, programmatic challenges, and gaps and suggests a way forward that can be adopted by NTEPs for LTBI. We searched the electronic databases of PubMed, Scopus, and Web of Science for studies published between 2010 to 2020 using MeSH terms: Latent TB Diagnosis, TB preventive therapy, Vaccines, LTBI, and HIV/ COVID.Expert opinion: NTEPs of developing countries should offer a better, point-of-care diagnostic, and effective treatment for LTBI to reduce the number of new TB cases arising from people infected with M.tb. Awareness about LTBI should be increased among the health system staff and the public. More funding is needed to advance research as well as implement the newer findings in the NTEP to achieve the End TB targets by 2035.