Abstract
BackgroundIndia has generally used 1 TU purified protein derivative (PPD) as opposed to 2 TU PPD globally, limiting comparisons. It is important to assess latent TB infection in adolescents given that they may be a target group for new post-exposure TB vaccines.The aim of this study is to describe the pattern and associations of tuberculin skin test (TST) responses (0.1 ml 2 TU) in adolescents in South India.Methods6643 school-going adolescents (11 to <18 years) underwent TST. Trained tuberculin reader made the reading visit between 48 and 96 hours after the skin testResultsOf 6608 available TST results, 9% had 0 mm, and 12% ≥10 mm responses. The proportion of TST positive (≥10 mm) was higher among older children, boys, those with a history of TB contact and reported BCG immunization Those with no TST response (0 mm) included younger participants (<14 years), those whose mothers were illiterate and those with a recent history of weight loss. Those of a higher socio-economic status (houses with brick walls, LPG gas as cooking fuel) and those with a visible BCG scar were less likely to be non-responders.ConclusionProportion of non-responders was lower than elsewhere in the world. Proportion of TST positivity was higher in those already exposed to TB and in children who had been BCG immunized, with a zero response more likely in younger adolescents and those with recent weight loss.Electronic supplementary materialThe online version of this article (doi:10.1186/s12879-014-0571-7) contains supplementary material, which is available to authorized users.
Highlights
India has generally used 1 Tuberculin units (TU) purified protein derivative (PPD) as opposed to 2 TU PPD globally, limiting comparisons
The population of this study were mixed with a large proportion of Bacillus calmette guerin (BCG) vaccinated adolescents including those with BCG scars
A total of 6643 adolescents were enrolled in the study, among them TST was administered to 6608 participants at baseline, 35 participants did not have a TST done; males and those who had illiterate mothers were more likely not to have had a TST done
Summary
India has generally used 1 TU purified protein derivative (PPD) as opposed to 2 TU PPD globally, limiting comparisons. In India, large epidemiological studies have used the tuberculin skin test (TST) to detect tuberculosis (TB) infection, calculate the annual risk of tuberculous infection (ARTI) as a measure of the TB transmission in a community) for different zones of the country, [1] as a means of evaluating the new case detection rate, and for monitoring TB case detection efforts of the Revised National Tuberculosis Control Programme (RNTCP) in TST data from India has conventionally used a dose of 1TU as opposed to the 2TU dose more universally used [5,6]. The intent was to obtain data that could be compared across countries (most of which use 2TU)
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