High tuberculosis burden among HIV-infected populations in Thailand due to a low-sensitivity tuberculin skin test.

The current Thai guideline recommends that among people living with HIV, isoniazid preventive therapy (IPT) should be given to those with a positive tuberculin skin test (TST). We conducted a case-control study, nested within a cohort study, in Chiang Rai Province in Thailand to determine the role of TST in predicting the development of active tuberculosis (TB) within the following 2 years. Comparison between participants with CD4+ counts <50cells/mm3 to those with CD4+ ≥200cells/mm3 revealed that TST results were less sensitive (7.7% vs 50.0%) and had a lower negative predictive value (73.1% vs 97.3%) in those with a CD4+ count <50cells/mm3. In people with HIV, using a positive TST result as a criterion for initiating IPT inadvertently decreases the benefits of IPT, especially among those with low CD4+ counts.