Zhao J, Yuan Q, Wang H, et al. - In view of the emergence of novel coronavirus SARS-CoV-2, researchers sought to determine the antibody response in infected patient, and to ascertain the clinical values of antibody testing. They collected serial plasma samples (n = 535) from a total of 173 patients with SARS-CoV-2 infection during the hospitalization and testes these for total antibodies (Ab), IgM and IgG against SARS-CoV-2. The seroconversion rate for Ab, IgM and IgG was 93.1%, 82.7% and 64.7%, respectively. For Ab, IgM and then IgG, the median seroconversion time was day-11, day-12 and day-14, separately. Among patients, the presence of antibodies was < 40% within 1-week since onset; it increased rapidly increased to 100.0% (Ab), 94.3% (IgM) and 79.8% (IgG) since day-15 after onset. In contrast, there was a decrease in RNA detectability from 66.7% (58/87) in samples collected before day-7 to 45.5% (25/55) during day 15-39. Significant improvement in the sensitivity of pathogenic diagnosis for COVID-19 was observed when RNA and antibody detection are combined; this improvement was evident even in early phase of 1-week since onset. Moreover, there was an independent association of a higher titer of Ab with a worse clinical classification. These findings support that serological testing could be used in routine practice for the diagnosis and management of COVID-19 patients.