Background: New blood test (QuantiFERON-TB-2G: QFT-2G), based on detection of IFN-gamma released by T cells in response to M. tuberculosis specific antigens, has the high sensitivity and specificity for diagnosis of tuberculosis. However, it is essential to evaluate this T cell-based approach in individuals with HIV-associated impairment in T cell immunity.
Methods: We assessed the usefulness of QFT-2G on diagnosis of tuberculosis in 13 HIV-infected patients with tuberculosis and the performance of 25 HIV infected persons under highly active antiretroviral treatment (HAART). QFT-2G, CD4 counts, and tuberculosis skin test and so on were examined.
Results: The sensitivity of QFT-2G in HIV-infected patients with tuberculosis was 76.9%, which was significantly higher compared with tuberculin skin test, 15.4%. There was one indeterminate case of which CD4 count was 16/microl, the lowest count among the all patients. CD4 counts of 25 HIV infected persons under HAART were between 100 and 1157/microl. There were 3 QFT-2G positive cases among them, who had past history of tuberculosis.
Conclusion: Although the very low CD4 counts in HIV-infected patients might adversely affect QFT-2G performance, the sensitivity of QFT-2G in the most of HIV-infected patients with tuberculosis was high, and it was thought that it was useful enough to diagnose tuberculosis infection. Careful observation is required in whether the recurrence of tuberculosis takes place among QFT-2G positive persons who have past history of tuberculosis.