Abstract

The use of high-quality antigen-specific immunoassays for detecting anti-neutrophil cytoplasmic antibodies (ANCA) and anti-glomerular basement membrane (GBM) autoantibodies is recommended in patients with suspected ANCA vasculitis and/or anti-GBM disease. We analysed the diagnostic performance of a semi-quantitative and rapid immunoblot (EUROIMMUN AG, Lübeck, Germany) in two settings. Patient sera from different cohorts (ANCA vasculitis n = 187, anti-GBM disease n = 19, and disease controls n = 51) were used. The diagnostic performance of the immunoblot was assessed when used as a confirmatory test for the presence of ANCA in suspected ANCA vasculitis and when evaluating the presence of ANCA and/or anti-GBM antibodies in AAV and/or anti-GBM disease patients with a rapidly progressive glomerulonephritis (RPGN). In a confirmatory test setting, the immunoblot had an optimal sensitivity and specificity of 97.4 and 98.1% for PR3-ANCA and 98.5 and 96.4% for MPO-ANCA, respectively. With increasing test result ranges, a higher interval likelihood ratio (LR) was found for both ANCA entities. When evaluating for ANCA in patients with RPGN, the highest diagnostic accuracy (sensitivity 92.9% and specificity 100%) was obtained by using different cut-off values of positivity for PR3- (>5) and MPO-ANCA (>10). Also, the diagnostic performance for detecting anti-GBM was good (sensitivity 100% and specificity 100%). There are advantages over other assays in terms of time, costs, and interpretation of results. The immunoblot is a useful addition to current guidelines, particularly when a rapid diagnosis is necessary.

摘要

对于疑似 ANCA 血管炎和/或抗 GBM 疾病的患者，建议使用高质量的抗原特异性免疫分析检测抗中性粒细胞胞浆抗体 (ANCA) 和抗肾小球基底膜 (GBM) 自身抗体。我们在两种情况下分析了半定量和快速免疫印迹（EUROIMMUN AG，Lübeck，Germany）的诊断性能。来自不同队列的患者血清（ANCA 血管炎n  = 187，抗 GBM 疾病n  = 19，疾病对照n = 51) 被使用。当用作疑似 ANCA 血管炎中 ANCA 存在的确认试验，以及评估 AAV 和/或抗 GBM 疾病患者中 ANCA 和/或抗 GBM 抗体的存在时，免疫印迹的诊断性能是评估的。进行性肾小球肾炎（RPGN）。在验证性测试环境中，免疫印迹对 PR3-ANCA 的最佳灵敏度和特异性分别为 97.4% 和 98.1%，对 MPO-ANCA 的最佳灵敏度和特异性分别为 98.5% 和 96.4%。随着测试结果范围的增加，发现两个 ANCA 实体的区间似然比 (LR) 更高。在评估 RPGN 患者的 ANCA 时，通过使用不同的 PR3- (>5) 和 MPO-ANCA (>10) 阳性截止值获得最高的诊断准确性（敏感性 92.9% 和特异性 100%）。还，检测抗GBM的诊断性能良好（敏感性100%，特异性100%）。在时间、成本和结果解释方面，与其他分析相比具有优势。免疫印迹是对当前指南的有用补充，尤其是在需要快速诊断时。