Hueston Linda, Kok Jen, Guibone Ayla, McDonald Damien, Hone George, Goodwin James, Carter Ian, Basile Kerri, Sandaradura Indy, Maddocks Susan, Sintchenko Vitali, Gilroy Nicole, Chen Sharon, Dwyer Dominic E, O'Sullivan Matthew V N
New South Wales Health Pathology, Institute of Clinical Pathology and Medical Research, Westmead, Australia.
Department of Infectious Diseases, Westmead Hospital, Westmead, Australia.
Open Forum Infect Dis. 2020 Aug 27;7(9):ofaa387. doi: 10.1093/ofid/ofaa387. eCollection 2020 Sep.
Testing for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific antibodies has become an important tool, complementing nucleic acid tests (NATs) for diagnosis and for determining the prevalence of coronavirus disease 2019 (COVID-19) in population serosurveys. The magnitude and persistence of antibody responses are critical for assessing the duration of immunity.
A SARS-CoV-2-specific immunofluorescent antibody (IFA) assay for immunoglobulin G (IgG), immunoglobulin A (IgA), and immunoglobulin M (IgM) was developed and prospectively evaluated by comparison to the reference standard of NAT on respiratory tract samples from individuals with suspected COVID-19. Neutralizing antibody responses were measured in a subset of samples using a standard microneutralization assay.
A total of 2753 individuals were eligible for the study (126 NAT-positive; prevalence, 4.6%). The median "window period" from illness onset to appearance of antibodies (range) was 10.2 (5.8-14.4) days. The sensitivity and specificity of either SARS-CoV-2 IgG, IgA, or IgM when collected ≥14 days after symptom onset were 91.3% (95% CI, 84.9%-95.6%) and 98.9% (95% CI, 98.4%-99.3%), respectively. The negative predictive value was 99.6% (95% CI, 99.3%-99.8%). The positive predictive value of detecting any antibody class was 79.9% (95% CI, 73.3%-85.1%); this increased to 96.8% (95% CI, 90.7%-99.0%) for the combination of IgG and IgA.
Measurement of SARS-CoV-2-specific antibody by IFA is an accurate method to diagnose COVID-19. Serological testing should be incorporated into diagnostic algorithms for SARS-CoV-2 infection to identify additional cases where NAT was not performed and resolve cases where false-negative and false-positive NATs are suspected. The majority of individuals develop robust antibody responses following infection, but the duration of these responses and implications for immunity remain to be established.
严重急性呼吸综合征冠状病毒2（SARS-CoV-2）特异性抗体检测已成为一项重要工具，可作为核酸检测（NAT）的补充，用于诊断以及在人群血清学调查中确定2019冠状病毒病（COVID-19）的流行情况。抗体反应的强度和持久性对于评估免疫持续时间至关重要。
开发了一种针对免疫球蛋白G（IgG）、免疫球蛋白A（IgA）和免疫球蛋白M（IgM）的SARS-CoV-2特异性免疫荧光抗体（IFA）检测方法，并通过与疑似COVID-19个体呼吸道样本的NAT参考标准进行比较，进行前瞻性评估。使用标准微量中和试验在一部分样本中测量中和抗体反应。
共有2753人符合研究条件（126人NAT阳性；患病率为4.6%）。从发病到出现抗体的中位“窗口期”（范围）为10.2（5.8 - 14.4）天。症状出现后≥14天采集的SARS-CoV-2 IgG、IgA或IgM的敏感性和特异性分别为91.3%（95%CI，84.9% - 95.6%）和98.9%（95%CI，98.4% - 99.3%）。阴性预测值为99.6%（95%CI，99.3% - 99.8%）。检测任何抗体类别的阳性预测值为79.9%（95%CI，73.3% - 85.1%）；IgG和IgA联合检测时，该值增至96.8%（95%CI，90.7% - 99.0%）。
通过IFA检测SARS-CoV-2特异性抗体是诊断COVID-19的准确方法。血清学检测应纳入SARS-CoV-2感染的诊断算法中，以识别未进行NAT的其他病例，并解决疑似NAT假阴性和假阳性的病例。大多数个体在感染后会产生强烈的抗体反应，但这些反应的持续时间及其对免疫的影响仍有待确定。
