Whitworth William C, Goodwin Donald J, Racster Laura, West Kevin B, Chuke Stella O, Daniels Laura J, Campbell Brandon H, Bohanon Jamaria, Jaffar Atheer T, Drane Wanzer, Sjoberg Paul A, Mazurek Gerald H
Division of Tuberculosis Elimination, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America.
Epidemiology Services Branch, United States Air Force School of Aerospace Medicine, Brooks City-Base, Texas, United States of America.
PLoS One. 2014 Jan 23;9(1):e86721. doi: 10.1371/journal.pone.0086721. eCollection 2014.
The QuantiFERON®-TB Gold In-Tube test (QFT-GIT) detects Mycobacterium tuberculosis (Mtb) infection by measuring release of interferon gamma (IFN-γ) when T-cells (in heparinized whole blood) are stimulated with specific Mtb antigens. The amount of IFN-γ is determined by enzyme-linked immunosorbent assay (ELISA). Automation of the ELISA method may reduce variability. To assess the impact of ELISA automation, we compared QFT-GIT results and variability when ELISAs were performed manually and with automation.
Blood was collected into two sets of QFT-GIT tubes and processed at the same time. For each set, IFN-γ was measured in automated and manual ELISAs. Variability in interpretations and IFN-γ measurements was assessed between automated (A1 vs. A2) and manual (M1 vs. M2) ELISAs. Variability in IFN-γ measurements was also assessed on separate groups stratified by the mean of the four ELISAs.
Subjects (N = 146) had two automated and two manual ELISAs completed. Overall, interpretations were discordant for 16 (11%) subjects. Excluding one subject with indeterminate results, 7 (4.8%) subjects had discordant automated interpretations and 10 (6.9%) subjects had discordant manual interpretations (p = 0.17). Quantitative variability was not uniform; within-subject variability was greater with higher IFN-γ measurements and with manual ELISAs. For subjects with mean TB Responses ±0.25 IU/mL of the 0.35 IU/mL cutoff, the within-subject standard deviation for two manual tests was 0.27 (CI95 = 0.22-0.37) IU/mL vs. 0.09 (CI95 = 0.07-0.12) IU/mL for two automated tests.
QFT-GIT ELISA automation may reduce variability near the test cutoff. Methodological differences should be considered when interpreting and using IFN-γ release assays (IGRAs).
结核感染T细胞检测（QFT-GIT）通过检测（肝素化全血中的）T细胞受到特定结核分枝杆菌（Mtb）抗原刺激时释放的干扰素γ（IFN-γ）来检测结核分枝杆菌（Mtb）感染。IFN-γ的量通过酶联免疫吸附测定（ELISA）来确定。ELISA方法的自动化可能会减少变异性。为了评估ELISA自动化的影响，我们比较了手动和自动化进行ELISA时的QFT-GIT结果及变异性。
将血液采集到两组QFT-GIT管中并同时进行处理。对于每组，在自动化和手动ELISA中测量IFN-γ。评估自动化（A1与A2）和手动（M1与M2）ELISA之间解释和IFN-γ测量的变异性。还根据四次ELISA的平均值对不同组进行分层，评估IFN-γ测量的变异性。
146名受试者完成了两次自动化和两次手动ELISA。总体而言，16名（11%）受试者的结果不一致。排除一名结果不确定的受试者后，7名（4.8%）受试者的自动化解释不一致，10名（6.9%）受试者的手动解释不一致（p = 0.17）。定量变异性并不一致；IFN-γ测量值越高且采用手动ELISA时，受试者内部变异性越大。对于结核菌素平均反应在0.35 IU/mL临界值±0.25 IU/mL范围内的受试者，两次手动检测的受试者内部标准差为0.27（95%CI = 0.22 - 0.37）IU/mL，而两次自动化检测为0.09（95%CI = 0.07 - 0.12）IU/mL。
QFT-GIT ELISA自动化可能会减少检测临界值附近的变异性。在解释和使用IFN-γ释放检测（IGRAs）时应考虑方法学差异。
