Abstract
BACKGROUND: The unsatisfactory accuracy and capacity of real time RT-PCR depends on several unavoidable reasons, which cannot meet the demands for COVID-19 diagnosis. METHODS: 206 serum samples were collected from patients who were treated in the General Hospital of the Central Theater Command of the PLA between January 18 and April 4, 2020. 270 serum samples from healthy blood donors were used as control. IgM and total antibodies (Ab) against SARS-CoV-2 were detected by Chemiluminescence Microparticle Immunoassay (CMIA). RESULTS: Among the 206 patients, the positive rate of IgM and Ab were 149/206 (72.3 %) and 187/206 (90.8 %), respectively. And the specificity of IgM and Ab detection were 99.3 % and 98.9 %, respectively. The sensitivity of CMIA for Ab detection was significantly higher than that of IgM. An increase of the positive rate and S/CO value for detecting IgM and Ab accompanied with the increasing of days post-disease onset (d.p.o.) were observed. The positive rate of Ab detected by CMIA increased rapidly after 7 d.p.o., while that of IgM was obviously increased after 14 d.p.o.. In addition, the age and gender of these patients did not affect the seroconversion and titer of antibodies during the whole course. The disease-severity of patients had no effect on the seroconversion of antibodies. However, the critical patients possessed a much higher antibody titers than the no-critical cases after 14 d.p.o.. CONCLUSIONS: The CMIA can provide important complementation to nucleic acid assay and help to enhance the accuracy and capacity of diagnosis of SARS-CoV-2 infection.