1.2 methods
The SARS-CoV-2 nucleic acid extraction reagent (Magnetic bead method, Jiangsu Master Biotechnology Co., LTD. of China, item No: SDK60104) was used to extract viral nucleic acid with the aid of the automatic nucleic acid extraction instrument (Jiangsu Master Biotechnology Co., Ltd. of China, item No: SSNP-3000A). Open reading frame 1ab (ORF1ab) and nucleocapsid (N) gene of dual nucleic acid detection kit was used for SARS-CoV-2 nucleic acid reverse transcription and amplification reagents (Shanghai Huirui Biotechnology Co., LTD. of China, product no.: vr-ii-120). Interpretation criteria: The value of cycle threshold (Ct) ≥ 39.2 means the genes to be tested were negative; The Ct value < 35 means the gene to be tested was positive; While the Ct value between 35 and 39.2, the results are in the grey area and the test should be repeated. Once repeated, if the Ct value ≥ 39.2, the result was negative; however, if the Ct value < 39.2 the result was positive. SARS-CoV-2 antibody detection kit (colloidal gold method, Guangzhou Wanfu Biotechnology Co., LTD. of China) and SARS-CoV-2 of IgM and IgG detection kit (chemiluminescence method, Shenzhen Ya Huilong Biotechnology Co., LTD. of China) were used for serum antibody assays and analyzed with a IFlash3000 automatic chemiluminescent immune analyzer (Shenzhen Ya Huilong biological technology Co., LTD. of China). Interpretation criteria: samples with IgM and IgG concentrations < 10.0 AU/ml are non-reactive (negative), while the concentrations ≥10.0 AU/ml are reactive (positive). All tests were conducted under manufacturing instructions for all of these kits.