Frequency of positive tuberculin skin test in BCG-vaccinated asymptomatic adults in Pakistan

ABSTRACT

To determine the frequency of positive tuberculin skin test [TST] in BCG-vaccinated asymptomatic healthy Pakistani adults. Cross sectional study. The study was carried out in Military Hospital, Rawalpindi in 2008 over six months. One hundred and thirty six individuals fulfilling inclusion and exclusion criteria of study were recruited after consent. They were subjected to TST [Mantoux test] and results were interpreted after 72 hours of injection. Test was recorded as positive if the indurated area was >/= 10 mm, and strongly positive if >/= 15 mm. All participants were male with the mean age of 26.35 +/- 6.164 years. The overall frequency of positive TST was 41.2%. Out of these, 9.6% were strongly positive. In healthy, BCG-vaccinated adult Pakistani population, TST is found to be positive in high frequency, and even induration of more than 15 mm was seen in significant number. In view of low specificity, TST should not be relied upon for the diagnosis of active tuberculosis [TB]