Background:  Guidelines for tuberculosis (TB) detection are not being implemented in Thailand. Treatment of latent TB infection can prevent active TB and reduce mortality and morbidity of TB/HIV-co-infected patients.

Methods:  Anonymous clinic conducted this prospective cohort by screening and treating of latent TB infections since January 2005. TST with induration ≤5 mm was considered positive. Active TB was excluded by clinical and chest X-ray.Clients with a positive TST (TST+ve), normal chest X-ray and asymptomatic for TB were considered as latent TB infections and received 9 months of isoniazid (INH) chemoprophylaxis. Relationships between a TST+ve, client demographic, ART use, and CD4 count was done using c², multiple logistic regression models and odd ratio.

Results:  From January to Aug 2005, TST was done in 1078 HIV-infected clients without history of active TB:  79% were asymptomatic with mean age of 33 years; 38% were women and 22% were currently on ART. CD4 were available in 88%. TST was positive in 259 (24%). The rate of TST+ve was lowest among clients with CD4≤200 cells/mm³. Multivariate analysis showed significant correlation between a TST+ve and CD4 >200 cells/mm³, male sex, and ART use (p <0.05). Of the 259 clients with TST+ve, 237(92%) clients received INH chemoprophylaxis. Active TB was diagnosed in 14 (1.3%) clients, all were ART-naïve at the time of TST: 10 of whom were diagnosed during the process of excluding active TB, 3developed active TB during INH chemoprophylaxis (2 after 3 months and 1 after 1 month of INH treatment and all had TB in lymph nodes), and 1 with TST-negative had pulmonary TB 3 months later. Of the 14, 11 (79%) had CD4 ≤200 cells/mm³ (including 1 TST-negative and 10 TST+ve). Clients with CD4 ≤200 cells/mm³ and TST+ve had an 82 times higher risk of having active TB (OR = 82; 95%CI 10 to 667) compared with those who were TST-negative and CD4 ≤200 cells/mm³.

Conclusions:  TST can identify HIV-infected persons who should receive a full investigation to exclude active TB. In this case is the HIV-infected persons with CD4 ≤200 cells/mm³ and TST+ve. In our study, HIV-infected persons with the highest chance of having a TST+ve were men currently taking ART with CD4 >200cells/mm³.