Coronavirus Disease 2019 (COVID-19) convalescent plasma (CCP) was approved by the FDA for use in severe cases of COVID-19 under an emergency Investigational New Drug (IND) protocol. Eligibility criteria for CCP donors includes documentation of evidence of COVID-19 either by viral RNA detection at the time of illness or positive SARS-CoV-2 IgG after recovery if diagnostic testing for COVID-19 was not performed at the time of illness. In addition to analysis of CCP, analysis of SARS-CoV-2 IgG provides information for possible past exposure and may support diagnosis when SARS-CoV-2 PCR is negative and clinical suspicion for COVID-19 is high. Furthermore, assays with high sensitivity and specificity for SARS-CoV-2 IgG are critical for understanding community exposure rates to SARS-CoV-2. Currently, there are several assays that test for antibodies to SARS-CoV-2 using a variety of methods, including point-of-care lateral flow-based devices, high throughput immunoassay analyzers, and manual methods such as ELISA. These assays target a number of SARS-CoV-2 antigens, including the nucleocapsid protein (N), full length spike protein (S), S1 subunit, or receptor binding domain (RBD) of the S protein. Given the heterogeneity among methods for, and antigenic targets used in SARS-CoV-2 antibody assays, it is necessary for careful evaluation of these assays prior to implementation for clinical use. We compared two assays that had received the CE mark of regulatory approval and that used either the N antigen or S1-RBD antigen as the target for analysis of a large set of CCP samples. Our data indicates that sensitivity and specificity vary between these assays and that more than one antigenic target may be required to improve the sensitivity and specificity of IgG detection to SARS-CoV-2.

FDA批准了2019年冠状病毒病（COVID-19）的恢复期血浆（CCP）在严重的COVID-19病例中用于紧急研究新药（IND）协议。CCP捐献者的资格标准包括在患病时通过病毒RNA检测或康复后（如果在患病时未对COVID-19进行诊断性检测）通过病毒RNA检测或恢复后呈阳性SARS-CoV-2 IgG的证据证明。除了分析CCP之外，SARS-CoV-2 IgG的分析还提供了可能的过去暴露信息，当SARS-CoV-2 PCR阴性且临床对COVID-19的怀疑很高时，可以支持诊断。此外，对SARS-CoV-2 IgG具有高灵敏度和特异性的测定对于了解社区对SARS-CoV-2的暴露率至关重要。目前，有多种使用多种方法测试SARS-CoV-2抗体的检测方法，包括基于即时点侧向流动的设备，高通量免疫分析仪和手动方法（如ELISA）。这些测定法靶向许多SARS-CoV-2抗原，包括核衣壳蛋白（N），全长刺突蛋白（S），S1亚基或S蛋白的受体结合域（RBD）。鉴于SARS-CoV-2抗体检测方法之间的异质性以及所使用的抗原靶标，在进行临床应用之前有必要仔细评估这些检测方法。我们比较了两种已获得监管机构批准的CE标志且使用N抗原或S1-RBD抗原作为分析大量CCP样品的靶标的测定法。