Tuberculin test is a cheap and easily available test. In which of the following situations there is high failure in the interpretation of the test?
(A) High percentage of immunized people (B) HIV cases are less (C) High prevalence of disease (D) Environmental mycobacterium infections are less
(A) Ans: A. High percentage of immunized people(Ref Park 24/e p195-196, 23/e p186)High failure of tuberculin test:High percentage of immunized people - Due to higher BCG coverage producing tuberculin hypersensitivity.Exaggerated responses:In presence of atypical mycobacteria infection & 'boosting effect' of second tuberculin dose producing larger reaction than 1st.Tuberculin test lost its sensitivity as an indicator of true prevalence of infection.