Emergence of coronavirus disease 2019 (COVID-19) is a major healthcare threat. Current method of detection involves qPCR-based technique, which identifies the viral nucleic acids when present in sufficient quantity. False negative results can be achieved and failure to quarantine the infected patient would be a major setback in containing the viral transmission. We here aim to describe the time kinetics of various antibodies produced against the 2019 novel coronavirus (SARS-CoV-2) and evaluate the potential of antibody testing to diagnose COVID-19.
The host humoral response against SARS-CoV-2 including IgA, IgM and IgG response were examined by using an ELISA based assay on the recombinant viral nucleocapsid protein. Total 208 plasma samples were collected from 82 confirmed and 58 probable cases (qPCR negative but had typical manifestation). The diagnostic value of IgM was evaluated in this cohort.
The median duration of IgM and IgA antibody detection were 5 days (IQR 3-6), while IgG was detected on 14 days (IQR 10-18) after symptom onset, with a positive rate of 85.4%, 92.7% and 77.9% respectively. In confirmed and probable cases, the positive rates of IgM antibodies were 75.6% and 93.1%, respectively. The detection efficiency by IgM ELISA is higher than that of qPCR method after 5.5 days of symptom onset. The positive detection rate is significantly increased (98.6%) when combined IgM ELISA assay with PCR for each patient compare with a single qPCR test (51.9%).
Humoral response to SARS-CoV-2 can aid to the diagnosis of COVID-19, including subclinical cases.