Guo L, Ren L, Yang S, et al. - Researchers sought to delineate the time kinetics of various antibodies produced against the 2019 novel coronavirus (SARS-CoV-2). In addition, they evaluated the potential of antibody testing to diagnose COVID-19. Using an ELISA based assay on the recombinant viral nucleocapsid protein, they examined the host humoral response against SARS-CoV-2 including IgA, IgM and IgG response. Eighty two confirmed and 58 probable cases (qPCR negative but had typical manifestation) provided total 208 plasma samples. Evaluation of the diagnostic value of IgM was done. The median duration of IgM and IgA antibody detection were 5 days (IQR 3-6), while IgG was identified on 14 days (IQR 10-18) after symptom onset; these three had a positive rate of 85.4%, 92.7% and 77.9% respectively. Significant increase in positive detection rate was observed (98.6%) when combined IgM ELISA assay with PCR for each patient compare with a single qPCR test (51.9%). Outcomes support humoral response to SARS-CoV-2 as possibly valuable for diagnosing COVID-19, including subclinical cases.