QuantiFERON-TB Gold Plus (QFT-Plus) is the most widely used interferon gamma release assay (IGRA) for the diagnosis of latent tuberculosis infection (LTBI). The aim of this study was to compare QFT-Plus results by enzyme-linked immunosorbent assay (ELISA) on the SkyLab system with those obtained with chemiluminescence immunoassay (CLIA) on the Liaison XL analyzer. Agreement between the two assays was evaluated on 419 QFT-Plus blood samples and was found to be substantial (75.4%); higher agreement was found for positive (95.4%) and negative (80.4%) results, while most discordances were due to ELISA-indeterminate/CLIA-determinate results. According to Italian Clinical Microbiologist Association recommendations, in samples (n = 79) with a borderline result in ELISA (0.20 to 0.70 IU/ml), CLIA median values statistically increased (from 0.29 to 0.59 IU/ml for TB1 and from 0.32 to 0.60 IU/ml for TB2) but remained in the borderline range. Linear regression analysis indicated a substantial correlation between ELISA and CLIA for antigen tubes TB1 (Pearson’s r = 0.8666) and TB2 (Pearson’s r = 0.8728), but CLIA produced higher values than ELISA. Receiver operating characteristic (ROC) analysis showed that the optimal cutoff value in CLIA was 0.45 IU/ml for TB1 and 0.46 IU/ml for TB2. In conclusion, automated QFT-Plus with CLIA is comparable to QFT-Plus performed by ELISA. Within the linearity range of the test, CLIA detects higher quantitative values than ELISA, resulting in a higher number of determinate results and the conversion of samples that were close to the cutoff into positive borderline results. A higher cutoff for QFT-CLIA needs to be defined based on clinical diagnostic criteria.

中文翻译：

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具有化学发光免疫测定的QuantiFERON-TB Gold Plus：我们需要更高的临界值吗？

QuantiFERON-TB Gold Plus（QFT-Plus）是用于诊断潜伏性结核感染（LTBI）的最广泛使用的干扰素伽马释放测定（IGRA）。这项研究的目的是比较在SkyLab系统上通过酶联免疫吸附测定（ELISA）进行的QFT-Plus结果与在Liaison XL分析仪上进行化学发光免疫测定（CLIA）获得的结果。在419个QFT-Plus血样上评估了这两种测定之间的一致性，发现一致性很高（75.4％）；发现阳性（95.4％）和阴性（80.4％）结果的一致性更高，而大多数不一致之处是由于ELISA不确定/ CLIA确定的结果。根据意大利临床微生物学家协会的建议，在样品中（n= 79）并在ELISA中产生临界结果（0.20至0.70 IU / ml），CLIA中位数在统计学上有所提高（TB1从0.29增至0.59 IU / ml，TB2从0.32增至0.60 IU / ml），但仍处于临界范围内。线性回归分析表明抗原管TB1（Pearson's r = 0.8666）和TB2（Pearson's r）的ELISA和CLIA之间存在显着相关性= 0.8728），但是CLIA产生的值比ELISA高。接收器工作特性（ROC）分析显示，对于CLIA，CLIA的最佳临界值为0.45 IU / ml，对于TB2为0.46 IU / ml。总之，带有CLIA的自动QFT-Plus与ELISA进行的QFT-Plus相当。在测试的线性范围内，CLIA比ELISA检测到更高的定量值，从而导致更多的确定结果，并将接近临界值的样品转化为阳性临界结果。需要根据临床诊断标准定义更高的QFT-CLIA临界值。