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.