Dasari Harika, Bourassa Claude, Renaud Christian, Tremblay Cécile, Ducharme Francine M
Clinical Research and Knowledge Transfer Unit on Childhood Asthma, Centre Hospitalier Universitaire Sainte-Justine, Montreal, Québec, Canada.
Departments of Biomedical Sciences, Faculty of Medicine, Universite de Montreal, Montreal, Québec, Canada.
Microbiol Spectr. 2025 Jul;13(7):e0335024. doi: 10.1128/spectrum.03350-24. Epub 2025 Jun 2.
The NADAL COVID-19 IgG/IgM (NADAL) assay, approved for rapid testing on serum or plasma, had not been approved nor tested as a point-of-care test on capillary blood. The study aim was to evaluate the performance of NADAL compared to that of the DiaSorin Liaison SARS-CoV-2 S1/S2 IgG (DiaSorin) assay (gold standard). We conducted two cross-sectional studies in participants aged ≥2 years, in whom different blood substrates (whole blood vs serum) and sources (venous vs capillary) were sampled. The co-primary endpoints were agreement in IgG detection between NADAL on venous serum and whole capillary blood vs DiaSorin on venous serum. Among 128 participants, 23.2% had a positive DiaSorin IgG assay. The NADAL IgG on venous serum exhibited near-perfect agreement (κ = 0.91) and high accuracy (0.94, 95% CI: 0.87-1.00), with a sensitivity of 0.88 and perfect specificity compared to DiaSorin; NADAL IgG on whole capillary blood exhibited moderate agreement (κ = 0.77) and accuracy (0.84, 95% CI: 0.73-0.95), with a sensitivity of 0.68 and perfect specificity. As for secondary outcomes, when the two assays were compared within the same source (venous or capillary) but with different substrates (NADAL on whole blood vs DiaSorin on serum), strong agreement and high accuracy were observed. Within-test DiaSorin IgG assay on capillary vs venous serum showed near-perfect agreement and high accuracy. Within-test NADAL IgG assays on whole capillary blood vs capillary or venous serum demonstrated high accuracy. In conclusion, NADAL on venous serum exhibited near-perfect agreement and high accuracy with DiaSorin on venous serum but lower between-test performance on different blood substrates.
Accurate serological assays are essential for assessing population immunity levels and identifying vulnerable subgroups with lower immunity on which to focus vaccination efforts. Although rapid tests may offer the possibility of easy point-of-care testing on whole capillary blood for these purposes, they may not be as robust as other assays when used on different blood substrates or sources than those in which they were approved. The observed variability in test performance across different substrates and blood sources highlights the importance of pretesting assays under the specific conditions in which they would be used to ensure optimal interpretation of the immune status in the community.
NADAL新冠病毒IgG/IgM（NADAL）检测法已获批用于血清或血浆的快速检测，但尚未获批用于毛细血管血的即时检验，也未进行相关测试。本研究旨在评估NADAL检测法与DiaSorin Liaison SARS-CoV-2 S1/S2 IgG（DiaSorin）检测法（金标准）相比的性能。我们对年龄≥2岁的参与者进行了两项横断面研究，采集了不同的血液样本（全血与血清）和来源（静脉血与毛细血管血）。共同主要终点是NADAL检测静脉血清和全毛细血管血中的IgG与DiaSorin检测静脉血清中的IgG之间的一致性。在128名参与者中，23.2%的DiaSorin IgG检测呈阳性。NADAL检测静脉血清中的IgG与DiaSorin相比显示出近乎完美的一致性（κ = 0.91）和高准确性（0.94，95%CI：0.87 - 1.00），灵敏度为0.88，特异性完美；NADAL检测全毛细血管血中的IgG显示出中等一致性（κ = 0.77）和准确性（0.84，95%CI：0.73 - 0.95），灵敏度为0.68，特异性完美。至于次要结果，当在相同来源（静脉血或毛细血管血）但不同样本（NADAL检测全血与DiaSorin检测血清）中比较这两种检测法时，观察到高度一致性和高准确性。DiaSorin IgG检测法在毛细血管血清与静脉血清之间显示出近乎完美的一致性和高准确性。NADAL IgG检测法在全毛细血管血与毛细血管或静脉血清之间显示出高准确性。总之，NADAL检测静脉血清中的IgG与DiaSorin检测静脉血清中的IgG显示出近乎完美的一致性和高准确性，但在不同血液样本中的检测性能较低。
准确的血清学检测对于评估人群免疫水平和识别免疫力较低的脆弱亚组以集中开展疫苗接种工作至关重要。尽管快速检测可能为基于这些目的对全毛细血管血进行简易即时检验提供了可能性，但当用于不同于其获批的血液样本或来源时，它们可能不如其他检测法可靠。在不同样本和血液来源中观察到的检测性能差异凸显了在其将被使用的特定条件下对检测法进行预测试的重要性，以确保对社区免疫状态的最佳解读。
