Background The clinical utility of serial screening for tuberculosis (TB) by interferon-gamma release assays has not been established in HIV-1-infected individuals.
Methods In this prospective study HIV-1-infected subjects underwent repeated QuantiFERON-TB Gold In-Tube assay (QFT-GIT) testing at baseline and after 24 months to determine the rate of conversions and reversions in a low TB-incidence country. Data on demographics, history of tuberculosis and HIV-1 parameters were obtained and risk factors associated with conversion or reversion of QFT-GIT results were assessed in a multivariate regression model.
Results Of 846 HIV-1-infected subjects, 9% (76/846) were QFT-GIT positive, 85% (718/846) were QFT-GIT negative and 6% (52/846) QFT-GIT indeterminate at baseline, respectively. Concordant baseline and follow-up results were observed in 86% (686/794) of subjects. The observed inter-test agreement was 0.887 (95% CI: 0.847–0.899) while the inter-test agreement of serial QFT-GIT testing was moderate (Cohan κ-coefficient = 0.448). QFT-GIT conversions occurred in 9% (63/718) of individuals while QFT-GIT reversions were seen in 33% (25/76). Independent predictors for QFT-GIT conversion were origin from high TB incidence country (OR, 1.93; P = 0.024) and intravenous drug abuse (OR, 2.43; P = 0.016). Of the 10 active TB cases during follow-up 5 had concordant positive QFT-GIT results and 2 were QFT-GIT converters.
Conclusions TB screening in HIV-1 patients by serial QFT-GIT assays may be of clinical value due to its excellent reproducibility. However, QFT-GIT conversions and reversions should be interpreted carefully as their clinical significance remains to be established.
- interferon-γ release assay
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