Abstract
BackgroundRussia is one of 22 high burden tuberculosis (TB) countries. Identifying individuals, particularly health care workers (HCWs) with latent tuberculosis infection (LTBI), and determining the rate of infection, can assist TB control through chemoprophylaxis and improving institutional cross-infection strategies. The objective of the study was to estimate the prevalence and determine the relative risks and risk factors for infection, within a vertically organised TB service in a country with universal bacille Calmette-Guérin (BCG) vaccination.Methods and FindingsWe conducted a cross-sectional study to assess the prevalence of and risk factors for LTBI among unexposed students, minimally exposed medical students, primary care health providers, and TB hospital health providers in Samara, Russian Federation. We used a novel in vitro assay (for gamma-interferon [IFN-γ]) release to establish LTBI and a questionnaire to address risk factors. LTBI was seen in 40.8% (107/262) of staff and was significantly higher in doctors and nurses (39.1% [90/230]) than in students (8.7% [32/368]) (relative risk [RR] 4.5; 95% confidence interval [CI] 3.1–6.5) and in TB service versus primary health doctors and nurses: respectively 46.9% (45/96) versus 29.3% (34/116) (RR 1.6; 95% CI 1.1–2.3). There was a gradient of LTBI, proportional to exposure, in medical students, primary health care providers, and TB doctors: respectively, 10.1% (24/238), 25.5% (14/55), and 55% (22/40). LTBI was also high in TB laboratory workers: 11/18 (61.1%).ConclusionsIFN-γ assays have a useful role in screening HCWs with a high risk of LTBI and who are BCG vaccinated. TB HCWs were at significantly higher risk of having LTBI. Larger cohort studies are needed to evaluate the individual risks of active TB development in positive individuals and the effectiveness of preventive therapy based on IFN-γ test results.
Highlights
Identifying individuals with latent tuberculosis infection (LTBI) and their subsequent chemoprophylaxis is an important measure in preventing the development of active tuberculosis (TB), which can help to reduce the overall incidence and spread of TB.Russia is one of the 22 World Health Organization-defined high-incidence TB countries; high rates of drug resistance, including multi-drug resistance have been reported from several regions [2,3,4].Bacille Calmette-Guerin (BCG) vaccination is national policy in Russia and is administered to newborn babies and repeated at 7 and 14–15 years of age [5]
IFN-c assays have a useful role in screening health care workers (HCW) with a high risk of LTBI and who are bacille Calmette-Guerin (BCG) vaccinated
TB HCWs were at significantly higher risk of having LTBI
Summary
Identifying individuals with latent tuberculosis infection (LTBI) (considered to be persistence and multiplication of viable Mycobacterium tuberculosis bacilli within macrophages but without clinical manifestation of disease [1]) and their subsequent chemoprophylaxis is an important measure in preventing the development of active tuberculosis (TB), which can help to reduce the overall incidence and spread of TB.Russia is one of the 22 World Health Organization-defined high-incidence TB countries; high rates of drug resistance, including multi-drug resistance have been reported from several regions [2,3,4].Bacille Calmette-Guerin (BCG) vaccination is national policy in Russia and is administered to newborn babies and repeated at 7 and 14–15 years of age [5]. Identifying individuals, health care workers (HCWs) with latent tuberculosis infection (LTBI), and determining the rate of infection, can assist TB control through chemoprophylaxis and improving institutional cross-infection strategies. The researchers here had been studying the spread of tuberculosis in Samara City in southeastern Russia, where the rate of TB disease among health care workers was very high; in 2004 the number of TB cases among health care workers on TB wards was over ten times that in the general population. The researchers wanted to work out what proportion of health care workers in Samara City had latent TB infection, and to compare groups whom they thought would be at different levels of risk (students, clinicians outside of TB wards, clinicians on TB wards, etc.). In this study a new test was used, based on measuring the immune response to two proteins produced by M. tuberculosis, which are not present in the BCG vaccine strain
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