Diagnosis of latent tuberculosis infection among HIV-infected clients in Far North Queensland: use of an interferon-gamma release assay.

Latent Mycobacterium tuberculosis infection is a significant risk for those infected with HIV. We examined the use of an interferon-gamma release assay for the diagnosis of latent tuberculosis among HIV-infected clients attending two sexual health services in Far North Queensland. Of 240 clients tested, 19 returned a positive result (7.9%, 95% confidence interval (CI): 4.5-11.3%) and three were indeterminate (1.3%, 95% CI: -0.2%-2.7%). Low CD4 count was found to be significantly associated with an indeterminate test result (P = 0.004). However, we found no significant association between test results and client demographics, self-reported prior tuberculosis infection, Bacille Calmette-Guerin vaccine status or selected tuberculosis risk factors (P-values = 0.2-0.9).