Abstract
BackgroundThe tuberculin skin test (TST) is the recommended method for screening for Mycobacterium tuberculosis infection in many countries. We used this technique to assess bacillus Calmette-Guérin (BCG) status and to estimate the current prevalence and annual rate of latent tuberculosis infection in schoolchildren in the Central African Republic.MethodsTwo tuberculin units of 0.1 ml purified protein derivative TR23 were injected intradermally into the left forearm of 2710 children attending school in Bangui and Ombella M’Poko. The induration size was interpreted at cut-off points of ≥5 mm, ≥10 mm and ≥15 mm. The annual infection rate was estimated as the average number of infections in the study sample each year between birth and the time of the survey.ResultsOverall, there was no reaction to the TST (no induration) in 71.7 % (95 CI, 68.3–75.3 %) of BCG-vaccinated children and 82.9 % (95 CI, 74.1–91.4 %) of non-vaccinated children. The proportions of children who gave a TST reaction above ≥10 mm and ≥15 mm cut-off was 18.4 % (95 % CI, 16.8–20.1 %) and 8.9 % (95 % CI, 7.8–10.0 %), respectively. The proportions of TST reaction above these cut-offs were 19.6 % (95 % CI, 17.4–21.9 %) and 8.1 % (95 % CI, 6.7–9.6 %), respectively. The annual infection rate was 0.8 % at the cut-off point of ≥15 mm.ConclusionThis study provides updated data on rates of tuberculosis infection in the Central African Republic. It is remarkable that most of the children had negative tuberculin reactivity. More studies are required to understand the factors that determine the low tuberculin reactivity in this population.
Highlights
The tuberculin skin test (TST) is the recommended method for screening for Mycobacterium tuberculosis infection in many countries
The extent of TB infection in the Central African Republic has never been surveyed with the TST since establishment of the national programme, and the only data available on tuberculin reactivity in the country were reported in a survey conducted in 1988 in Bangui [10], which showed a Minime-Lingoupou et al BMC Public Health (2015) 15:496 prevalence of TB infection of 7.9 % and an estimated annual risk of 1.1 %
Of the 3280 children recruited for the survey, we excluded 174 who were absent at the time of testing, 87 who were absent at the skin test reading and 309 of unknown bacillus Calmette-Guérin (BCG) status, leaving 2710 (82.6 %) children for the final analysis, comprising 1469 (54.2 %) in Bangui and 1241 (45.8 %) in Ombella M’Poko
Summary
The tuberculin skin test (TST) is the recommended method for screening for Mycobacterium tuberculosis infection in many countries. The extent of TB infection in the Central African Republic has never been surveyed with the TST since establishment of the national programme, and the only data available on tuberculin reactivity in the country were reported in a survey conducted in 1988 in Bangui [10], which showed a Minime-Lingoupou et al BMC Public Health (2015) 15:496 prevalence of TB infection of 7.9 % and an estimated annual risk of 1.1 %. These figures rank the country among those with a low prevalence. The study reported here provides recent data on TST outcomes in both Bangui, the capital, and in the neighbouring rural area of Ombella M’Poko
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