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

Systematic review of the economic impact of novel Mycobacterium tuberculosis specific antigen-based skin tests for detection of TB infection compared with tuberculin skin test and interferon-gamma release assays

The Purified Protein Derivative tuberculin skin tests (TST) and blood-based Mycobacterium tuberculosis (M.tb) specific interferon-gamma release assays (IGRA) are the currently used tests for identifying individuals with TB infection for preventive treatment. However, challenges around access and implementation have limited their use. Novel M.tb specific skin tests (TBST) such as Diaskintest, ESAT6-CFP10 (C-TST), C-Tb (also known as Cy-Tb), and DPPD may provide accurate and scalable options but evidence synthesis on their economic impact is lacking. We conducted two separate systematic reviews to compare the costs and cost-effectiveness of (1) the novel skin tests TBST (primary), and (2) TST and IGRA tests (secondary), to support WHO guideline development. We searched for articles presenting economic evaluations of the diagnostic tests using a health provider perspective and related to TB infection in humans. We considered papers written in English, Chinese or Russian. In the primary review, eight studies for novel TBST were found. One study in Brazil assessed cost-effectiveness of C-TST and Diaskintest and seven in Russia assessed the Diaskintest, while none evaluated C-Tb or DPPD. The review showed on average, Diaskintest kit costs (in 2021 USD) $1.60 (1.50 - 1.70), while full unit costs were estimated at $5.07. C-TST unit cost was $9.96. The second review found 32 articles on IGRA and/or the TST. These presented an average TST full unit cost of $37.88, and $87.81 for IGRA. Studies' quality for TBST was limited while high-quality studies were found for TST and IGRA tests. In conclusion, there is limited evidence regarding the costs and cost-effectiveness of novel TBST. Conversely, there is substantial evidence for TST and IGRA tests, but most studies were performed in high-income and low-TB burden settings and their cost-effectiveness varied between and within risk groups without clear economic consensus.

Screening for latent tuberculosis in migrants-status quo and future challenges

OBJECTIVES

To review the evidence that migrants from tuberculosis (TB) high-incidence countries migrating to TB low-incidence countries significantly contribute to active TB cases in the counties of destination, primarily through reactivation of latent TB.

METHODS

This is a narrative review. The different screening programs in the countries of destination are reviewed either based on screening and preventive treatment of latent TB pre or more commonly - post arrival.

RESULTS

Screening can be performed using interferon-gamma release assays (IGRA) or tuberculin skin tests (TST). Preventive treatment of latent TB is using either monotherapy with isoniazid, or in combination with rifampicin or rifapentine. We discuss the ethical issues of preventive treatment in asymptomatic individuals and how these are addressed in different screening programs.

CONCLUSION

Screening migrants from TB high endemic countries to TB low endemic countries is beneficial. There is a lack of standardization and agreement on screening protocols, follow up and treatment.

Implementation of tuberculosis preventive therapy with INH-Rifapentine (3HP) for latent tuberculosis infection management in household tuberculosis contacts in India: A prospective study

OBJECTIVE

The primary objective of this study was to ascertain the acceptance, initiation, implementation and treatment completion rates of tuberculosis (TB) preventive therapy (TPT) using 3HP (INH-Rifapentine) among household contacts of microbiologically confirmed drug sensitive TB cases on anti-tubercular treatment under programmatic real-world settings. The secondary objectives were to estimate the prevalence and predictors of latent TB infection (LTBI) in household contacts of the index TB cases. We also ascertained the safety profile of the 3HP TPT regimen in the household contacts.

METHODS

This prospective observational study was conducted at 10 TB chest clinics in Delhi, India during 2022-2023. Household contacts aged 14 and older who tested positive for TB infection on a Tuberculin Skin test were initiated on the 3HP regimen. Logistic regression was performed by including statistically significant independent variables in multiple prediction models. p < 0.05 was considered statistically significant. STATA, version 15.1, was used to compute all analyses.

RESULTS

A total of 1067 (84.68%) eligible contacts of microbiologically confirmed, drug sensitive TB cases underwent screening with tuberculin skin test (TST), 614 (95.6%) LTBI positive contacts accepted the initiation of TPT, and 564 (91.8%) of those initiated on TPT completed the treatment. The major reason for refusal of screening was the lack of perception of risk of TB disease due to asymptomatic status. The prevalence of LTBI positivity through TST was 61.5% (95% CI, 58.5%, 64.4%). Adverse events were reported by 195 (31.8%) contacts initiated on 3HP of which 20 participants discontinued TPT. None of the sociodemographic factors showed a significant association with LTBI positivity (except age) or TPT completion rates.

CONCLUSION

LTBI management with 3HP is feasible among adolescent and adult household contacts in India with high rates of adherence from initiation until treatment completion. The maximum attrition of participants occurred at the time of screening for LTBI using TST.

Cost effectiveness analysis of single and sequential testing strategies for tuberculosis infection in adults living with HIV in the United States

Tuberculosis infection (TBI) frequently progresses to tuberculosis (TB) disease in people co-infected with human immunodeficiency virus (HIV). We examined the cost-effectiveness of single, sequential and no testing (total 12) strategies of TBI in HIV-infected people from the perspective of US healthcare provider. A decision-analytic model (20-year timeframe) was constructed to simulate TB-related outcomes: Direct medical cost and quality-adjusted life-years (QALYs). In the base-case analysis, the "confirm negative TST followed by QFT-Plus" strategy gained 0.1170 QALY at a total cost of USD3377. In the probabilistic sensitivity analysis of 10,000 Monte Carlo simulations, the probability of "confirm negative TST followed by QFT-Plus" to be accepted as cost-effective was the highest of all 12 strategies when the willingness-to-pay threshold exceeded 2340 USD/QALY. In conclusion, the strategy of "confirm negative TST followed by QFT-Plus" appears to be the preferred cost-effective option for TBI testing in HIV-infected people from the US healthcare provider's perspective.

Diagnostic Value of Interferon-Gamma Release Assays for Tuberculosis in the Immunocompromised Population

Interferon-gamma release assays (IGRAs) are widely used in the diagnosis of Mycobacterium tuberculosis (M. tuberculosis) infection by detecting interferon-γ released by previously sensitized T-cells in-vitro. Currently, there are two assays based on either enzyme-linked immunosorbent assay (ELISA) or enzyme-linked immunospot (ELISPOT) technology, with several generations of products available. The diagnostic value of IGRAs in the immunocompromised population is significantly different from that in the immunocompetent population because their results are strongly affected by the host immune function. Both physiological and pathological factors can lead to an immunocompromised situation. We summarized the diagnostic value and clinical recommendations of IGRAs for different immunocompromised populations, including peoplewith physiological factors (pregnant and puerperal women, children, and older people), as well as people with pathological factors (solid organ transplantation recipients, combination with human immunodeficiency virus infection, diabetes mellitus, end-stage renal disease, end-stage liver disease, and chronic immune-mediated inflammatory diseases). Though the performance of IGRAs is not perfect and often requires a combination with other diagnostic strategies, it still has some value in the immunocompromised population. Hopefully, the newly developed IGRAs could better target this population.