Interferon Gamma Release Assays for the Diagnosis of Latent TB Infection in HIV-Infected Individuals in a Low TB Burden Country

BackgroundInterferon gamma release assays (IGRAs) are used to diagnose latent tuberculosis infection. Two IGRAs are commercially available: the Quantiferon TB Gold In Tube (QFT-IT) and the T-SPOT.TB. There is debate as to which test to use in HIV+ individuals. Previous publications from high TB burden countries have raised concerns that the sensitivity of the QFT-IT assay, but not the T-SPOT.TB, may be impaired in HIV+ individuals with low CD4+ T-cell counts. We sought to compare the tests in a low TB burden setting. Methodology/Principal FindingsT-SPOT.TB, QFT-IT, and tuberculin skin tests (TST) were performed in HIV infected individuals. Results were related to patient characteristics. McNemar’s test, multivariate regression and correlation analysis were carried out using SPSS (SPSS Inc). 256 HIV infected patients were enrolled in the study. The median CD4+ T-cell count was 338 cells/µL (range 1–1328). 37 (14%) patients had a CD4+ T-cell count of Conclusions/SignificanceIn low TB prevalence settings, the QFT-IT yields more positive and fewer indeterminate results than T-SPOT.TB. Negative results on the QFT-IT and indeterminate/unavailable results on the T-SPOT.TB were more common in individuals with low CD4+ T-cell counts.研究背景：干扰素γ释放试验（Interferon gamma release assays, IGRAs）是潜伏性结核感染的常用诊断手段。目前已有两款商用IGRA试剂上市：Quantiferon TB Gold In Tube（QFT-IT）与T-SPOT.TB检测。针对HIV感染者应选用何种检测方法，学界尚存争议。此前来自结核高负担国家的研究指出，当CD4+T细胞计数较低时，QFT-IT的检测敏感性可能受损，但T-SPOT.TB的敏感性不受此类影响。本研究旨在结核低负担环境中对比两种检测方法的临床效能。 材料与方法/研究结果：本研究对HIV感染者同步开展T-SPOT.TB、QFT-IT及结核菌素皮肤试验（tuberculin skin tests, TST），并将检测结果与患者临床特征进行关联分析。采用SPSS公司软件完成麦克尼马尔检验、多元回归分析与相关性分析。本研究共纳入256名HIV感染者，其CD4+T细胞计数中位数为338个/µL（范围1~1328），其中37名（14%）患者的CD4+T细胞计数。 结论与意义：在结核低流行环境中，QFT-IT的阳性检出率高于T-SPOT.TB，且不确定结果的发生率更低。QFT-IT结果为阴性、以及T-SPOT.TB结果为不确定/无法获取的情况，在CD4+T细胞计数较低的感染者中更为常见。