By the end of year 2019, the new virus SARS-CoV-2 appeared, causing the Coronavirus Disease 2019 (COVID-19), and spread very fast globally. A continuing need for diagnostic tools is a must to contain its spread. Till now, the gold standard method, the reverse transcription polymerase chain reaction (RT-PCR), is the precise procedure to detect the virus. However, SARS-CoV-2 may escape RT-PCR detection for several reasons. The development of well-designed, specific and sensitive serological test like enzyme immunoassay (EIA) is needed. This EIA can stand alone or work side by side with RT-PCR.

In this study, we developed several EIAs including plates that are coated with either specially designed SARS-CoV-2 nucleocapsid or surface recombinant proteins. Each protein type can separately detect anti-SARS-CoV-2 IgM or IgG antibodies. For each EIAs, the cut-off value, specificity and sensitivity were determined utilizing RT-PCR confirmed Covid-19 and pre-pandemic healthy and other viruses-infected sera. Also, the receiver operator characteristic (ROC) analysis was performed to define the specificities and sensitivities of the optimized assay. The in-house EIAs were validated by comparing against commercial EIA kits. All in-house EIAs showed high specificity (98–99%) and sensitivity (97.8–98.9%) for the detection of IgG/IgM against RBD and N proteins of SARS-CoV-2.

From these results, the developed Anti-RBD and anti-N IgG and IgM antibodies EIAs can be used as a specific and sensitive tool to detect SARS-CoV-2 infection, calculate the burden of disease and case fatality rates.

到 2019 年底，新型病毒 SARS-CoV-2 出现，引发了 2019 年冠状病毒病 (COVID-19)，并在全球范围内迅速传播。对诊断工具的持续需求是遏制其传播的必要条件。到目前为止，金标准方法逆转录聚合酶链反应 (RT-PCR) 是检测病毒的精确方法。然而，由于多种原因，SARS-CoV-2 可能逃过 RT-PCR 检测。需要开发设计良好、特异性和灵敏的血清学测试，如酶免疫测定 (EIA)。该 EIA 可以单独使用，也可以与 RT-PCR 一起使用。

在这项研究中，我们开发了几种 EIA，包括涂有专门设计的 SARS-CoV-2 核衣壳或表面重组蛋白的板。每种蛋白质类型都可以单独检测抗 SARS-CoV-2 IgM 或 IgG 抗体。对于每个 EIA，使用 RT-PCR 确认的 Covid-19 和大流行前健康和其他病毒感染的血清来确定临界值、特异性和敏感性。此外，还进行了接受者操作特征 (ROC) 分析，以确定优化检测的特异性和敏感性。内部环境影响评估通过与商业环境影响评估套件进行比较得到验证。所有内部 EIA 在检测针对 SARS-CoV-2 的 RBD 和 N 蛋白的 IgG/IgM 时均显示出高特异性 (98–99%) 和敏感性 (97.8–98.9%)。

从这些结果来看，开发的抗 RBD 和抗 N IgG 和 IgM 抗体 EIA 可以用作检测 SARS-CoV-2 感染、计算疾病负担和病死率的特异性和灵敏工具。