IP-10 is an additional marker for tuberculosis (TB) detection in HIV-infected persons in a low-TB endemic country.

OBJECTIVE

In Indian HIV-infected patients, IP-10 response to QuantiFERON-TB Gold In tube (QFT-IT) antigens has been associated to tuberculosis (TB). However, specificity for active TB was lower than that reported by QFT-IT, making accuracy for TB detection questionable. To investigate this uncertainty, likely due to India being highly endemic for TB, and to better identify TB correlates, we evaluated the IP-10-based assay in HIV-infected subjects in Italy, a low-TB endemic country.

METHODS

195 individuals were prospectively enrolled; 118 were HIV-infected (21 with active TB, 97 without active TB, and distinguished as high/low-TB-risk). QFT-IT was performed and IP-10 was evaluated by ELISA.

RESULTS

Among the HIV-infected individuals, sensitivity for active TB was 66.7% by IP-10-based test and 52.4% (p = 1) by QFT-IT. IP-10-based assay showed a lower dependence on mitogen-response and CD4 counts than QFT-IT. Among subjects without active TB, a higher proportion of IP-10 responders was shown in high-TB-risk subjects than low-TB-risk subjects (40.0% vs 12.9%), similar to QFT-IT (37.1% vs 4.8%). Low-TB risk subjects showed 87.1% specificity for active TB by IP-10-based test vs 95.2% by QFT-IT.

CONCLUSIONS

In a low-TB endemic country, besides IFN-γ, IP-10 response to QFT-IT is associated with active TB and TB risk factors in HIV-infected patients with lower dependence on mitogen-response and CD4 counts.