A new and rapid approach for detecting COVID‐19 based on S1 protein fragments

The pandemic of novel coronavirus disease 2019 (COVID‐19) seriously threatened the public health all over the world. A colloidal gold immunochromatography assay for IgM/IgG antibodies against the receptor‐binding domain of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) S1 protein was established to assess its rapid diagnostic value. We first designed and manufactured all contents of the test cassette of SARS‐CoV‐2 rapid test kit: the colloidal gold‐labeled mouse‐antihuman lgM/lgG antibody, the recombinant SARS‐CoV‐2 antigen, the nitrocellulose membrane control line, and specimen diluents. Furthermore, reverse transcription‐polymerase chain reaction (RT‐PCR) assay, colloidal gold immunochromatography assay, serological validation of cross reaction with other common viruses, and clinical validation were performed. The kit was finally evaluated by 75 serum/plasma samples of SARS‐CoV‐2 infection cases and 139 healthy samples as control, with the result of that the sensitivity, specificity, and accuracy for IgM were 90.67%, 97.84%, and 95.33%, whereas for IgG were 69.33%, 99.28%, and 88.79%, respectively; the combination of IgM and IgG could improve the value: 92.00%, 97.12%, and 95.33%, respectively. Therefore, the rapid detection kit has high sensitivity and specificity, especially for IgM&IgG, showing a critical value in clinical application and epidemic control of COVID‐19.