Department of Laboratory Medicine, Yale University, New Haven, CT.
J Appl Lab Med. 2021 Jul 7;6(4):1005-1011. doi: 10.1093/jalm/jfab030.
SARS-CoV-2 serologic assays are becoming increasingly available and may serve as a diagnostic aid in a multitude of settings relating to past infection status. However, there is limited literature detailing the longitudinal performance of EUA-cleared serologic assays in US populations, particularly in cohorts with a remote history of PCR-confirmed SARS-CoV-2 infection (e.g., >2 months).
We evaluated the diagnostic sensitivities and specificities of the Elecsys® Anti-SARS-CoV-2 (anti-N) and Elecsys Anti-SARS-CoV-2 S (anti-S1-RBD) assays, using 174 residual clinical samples up to 267 days post-PCR diagnosis of SARS-CoV-2 infection (n = 154) and a subset of samples obtained prior to the COVID-19 pandemic as negative controls (n = 20).
The calculated diagnostic sensitivities for the anti-N and anti-S1-RBD assays were 89% and 93%, respectively. Of the 154 samples in the SARS-CoV-2-positive cohort, there were 6 discrepant results between the anti-N and anti-S1-RBD assays, 5 of which were specimens collected ≥200 days post-PCR positivity and only had detectable levels of anti-S1-RBD antibodies. When only considering specimens collected ≥100 days post-PCR positivity (n = 41), the sensitivities for the anti-N and anti-S1-RBD assays were 85% and 98%, respectively.
The anti-S1-RBD assay demonstrated superior sensitivity at time points more remote to the PCR detection date, with 6 more specimens from the SARS-CoV-2-positive cohort detected, 5 of which were collected more than 200 days post-PCR positivity. While analytical differences and reagent lot-to-lot variability are possible, this may indicate that, in some instances, anti-S1-RBD antibodies may persist longer in vivo and may be a better target for detecting remote SARS-CoV-2 infection.
SARS-CoV-2 血清学检测试剂的应用越来越广泛，可能在与过去感染状态相关的多种情况下作为诊断辅助手段。然而，关于美国人群中 EUA 批准的血清学检测试剂的纵向性能，尤其是在具有 PCR 确诊 SARS-CoV-2 感染的遥远病史的队列中（例如，>2 个月），文献资料有限。
我们评估了 Elecsys® Anti-SARS-CoV-2（抗 N）和 Elecsys Anti-SARS-CoV-2 S（抗 S1-RBD）检测试剂的诊断灵敏度和特异性，使用了 174 份残留临床样本，这些样本的 PCR 诊断 SARS-CoV-2 感染后时间长达 267 天（n=154），并选择了一部分在 COVID-19 大流行之前采集的样本作为阴性对照（n=20）。
抗 N 和抗 S1-RBD 检测试剂的计算诊断灵敏度分别为 89%和 93%。在 SARS-CoV-2 阳性队列的 154 份样本中，抗 N 和抗 S1-RBD 检测试剂之间有 6 份结果不一致，其中 5 份样本采集于 PCR 阳性后≥200 天，仅检测到抗 S1-RBD 抗体的可检测水平。当仅考虑采集于 PCR 阳性后≥100 天的样本（n=41）时，抗 N 和抗 S1-RBD 检测试剂的灵敏度分别为 85%和 98%。
抗 S1-RBD 检测试剂在距离 PCR 检测日期更远的时间点显示出更高的灵敏度，在 SARS-CoV-2 阳性队列中多检测到 6 份样本，其中 5 份样本采集于 PCR 阳性后超过 200 天。虽然可能存在分析差异和试剂批间变异性，但这可能表明，在某些情况下，抗 S1-RBD 抗体在体内可能持续存在更长时间，并且可能是检测遥远 SARS-CoV-2 感染的更好靶标。
