Cambridge Institute of Therapeutic Immunology & Infectious Disease, Cambridge, United Kingdom.
Department of Medicine, University of Cambridge, Cambridge, United Kingdom.
Am J Trop Med Hyg. 2023 Aug 14;109(4):890-894. doi: 10.4269/ajtmh.23-0179. Print 2023 Oct 4.
Determination of previous SARS-COV-2 infection is hampered by the absence of a standardized test. The marker used to assess previous exposure is IgG antibody to the nucleocapsid (IgG anti-N), although it is known to wane quickly from peripheral blood. The accuracies of seven antibody tests (virus neutralization test, IgG anti-N, IgG anti-spike [anti-S], IgG anti-receptor binding domain [anti-RBD], IgG anti-N + anti-RBD, IgG anti-N + anti-S, and IgG anti-S + anti-RBD), either singly or in combination, were evaluated on 502 cryopreserved serum samples collected before the COVID-19 vaccination rollout in Kumasi, Ghana. The accuracy of each index test was measured using a composite reference standard based on a combination of neutralization test and IgG anti-N antibody tests. According to the composite reference, 262 participants were previously exposed; the most sensitive test was the virus neutralization test, with 95.4% sensitivity (95% CI: 93.6-97.3), followed by 79.0% for IgG anti-N + anti-S (95% CI: 76.3-83.3). The most specific tests were virus neutralization and IgG anti-N, both with 100% specificity. Viral neutralization and IgG anti-N + anti-S were the overall most accurate tests, with specificity/sensitivity of 100/95.2% and 79.0/92.1%, respectively. Our findings indicate that IgG anti-N alone is an inadequate marker of prior exposure to SARS COV-2 in this population. Virus neutralization assay appears to be the most accurate assay in discerning prior infection. A combination of IgG anti-N and IgG anti-S is also accurate and suited for assessment of SARS COV-2 exposure in low-resource settings.
确定以前是否感染过 SARS-CoV-2 受到缺乏标准化检测手段的限制。目前用于评估既往暴露的标志物是核衣壳（IgG 抗-N）抗体，但已知其在外周血中迅速衰减。在加纳库马西 COVID-19 疫苗接种前采集的 502 份冷冻血清样本中，评估了七种抗体检测方法（病毒中和试验、IgG 抗-N、IgG 抗刺突[抗-S]、IgG 抗受体结合域[抗-RBD]、IgG 抗-N + 抗-RBD、IgG 抗-N + 抗-S 和 IgG 抗-S + 抗-RBD）单独或联合使用的准确性。每种指标检测方法的准确性均使用基于中和试验和 IgG 抗-N 抗体检测方法组合的复合参考标准来衡量。根据复合参考标准，262 名参与者以前曾接触过 SARS-CoV-2；最敏感的检测方法是病毒中和试验，敏感性为 95.4%（95%CI：93.6-97.3），其次是 IgG 抗-N + 抗-S 的 79.0%（95%CI：76.3-83.3）。最特异的检测方法是病毒中和试验和 IgG 抗-N，特异性均为 100%。病毒中和试验和 IgG 抗-N + 抗-S 是总体上最准确的检测方法，特异性/敏感性分别为 100/95.2%和 79.0/92.1%。我们的研究结果表明，在该人群中，单独的 IgG 抗-N 是 SARS-CoV-2 既往暴露的不足够的标志物。病毒中和试验似乎是区分既往感染的最准确检测方法。IgG 抗-N 和 IgG 抗-S 的组合也很准确，适合在资源匮乏的环境中评估 SARS-CoV-2 的暴露情况。
