Division of Tuberculosis Elimination, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America.
PLoS One. 2012;7(9):e43790. doi: 10.1371/journal.pone.0043790. Epub 2012 Sep 6.
The QuantiFERON®-TB Gold In-Tube test (QFT-GIT) is a viable alternative to the tuberculin skin test (TST) for detecting Mycobacterium tuberculosis infection. However, within-subject variability may limit test utility. To assess variability, we compared results from the same subjects when QFT-GIT enzyme-linked immunosorbent assays (ELISAs) were performed in different laboratories.
Subjects were recruited at two sites and blood was tested in three labs. Two labs used the same type of automated ELISA workstation, 8-point calibration curves, and electronic data transfer. The third lab used a different automated ELISA workstation, 4-point calibration curves, and manual data entry. Variability was assessed by interpretation agreement and comparison of interferon-γ (IFN-γ) measurements. Data for subjects with discordant interpretations or discrepancies in TB Response >0.05 IU/mL were verified or corrected, and variability was reassessed using a reconciled dataset.
Ninety-seven subjects had results from three labs. Eleven (11.3%) had discordant interpretations and 72 (74.2%) had discrepancies >0.05 IU/mL using unreconciled results. After correction of manual data entry errors for 9 subjects, and exclusion of 6 subjects due to methodological errors, 7 (7.7%) subjects were discordant. Of these, 6 (85.7%) had all TB Responses within 0.25 IU/mL of the manufacturer's recommended cutoff. Non-uniform error of measurement was observed, with greater variation in higher IFN-γ measurements. Within-subject standard deviation for TB Response was as high as 0.16 IU/mL, and limits of agreement ranged from -0.46 to 0.43 IU/mL for subjects with mean TB Response within 0.25 IU/mL of the cutoff.
Greater interlaboratory variability was associated with manual data entry and higher IFN-γ measurements. Manual data entry should be avoided. Because variability in measuring TB Response may affect interpretation, especially near the cutoff, consideration should be given to developing a range of values near the cutoff to be interpreted as "borderline," rather than negative or positive.
QuantiFERON®-TB Gold In-Tube 检测（QFT-GIT）是一种替代结核菌素皮肤试验（TST）检测结核分枝杆菌感染的可行方法。然而，个体内变异性可能会限制检测的实用性。为了评估变异性，我们比较了在不同实验室进行 QFT-GIT 酶联免疫吸附测定（ELISA）时同一受试者的结果。
在两个地点招募受试者，在三个实验室检测血液。两个实验室使用相同类型的自动化 ELISA 工作站、8 点校准曲线和电子数据传输。第三个实验室使用不同的自动化 ELISA 工作站、4 点校准曲线和手动数据输入。通过解释一致性和干扰素-γ（IFN-γ）测量值的比较来评估变异性。对解释不一致或 TB 反应 >0.05 IU/mL 有差异的受试者的数据进行验证或校正，并使用协调数据集重新评估变异性。
97 名受试者的结果来自三个实验室。11 名（11.3%）受试者的解释不一致，72 名（74.2%）受试者的 TB 反应 >0.05 IU/mL 存在差异。在纠正 9 名受试者的手动数据输入错误，以及排除 6 名因方法学错误的受试者后，7 名（7.7%）受试者的解释不一致。其中，6 名（85.7%）受试者的所有 TB 反应均在制造商推荐的截定点 0.25 IU/mL 以内。观察到非均匀测量误差，较高的 IFN-γ 测量值存在更大的变异性。TB 反应的个体内标准差高达 0.16 IU/mL，对于 TB 反应在截定点 0.25 IU/mL 以内的受试者，其一致性界限范围为 -0.46 至 0.43 IU/mL。
更大的实验室间变异性与手动数据输入和较高的 IFN-γ 测量值有关。应避免手动数据输入。由于测量 TB 反应的变异性可能会影响解释，特别是在截定点附近，因此应考虑在截定点附近开发一系列值作为“边界”来解释，而不是阴性或阳性。
