Abstract: Objective To investigate the clinical value of blood cell count, C-reactive protein and novel coronavirus (SARS-CoV-2) specific IgM antibody in the diagnosis of COVID-19. Methods The peripheral blood leukocyte, lymphocyte counts and C-reactive protein in 59 patients diagnosed with COVID-19 were detected and analyzed,and the level of SARS-CoV-2 specific IgM antibody in serum of patients with different course of disease were detected by colloidal gold immunochromatography. Results ①Among the 59 patients, 57 (96.61%) had normal or decreased leukocyte count,20 (33.9%) had decreased lymphocyte count and 41 (69.49%) had increased C-reactive protein.Compared with the healthy people, there were significant differences in the counts of leukocytes, lymphocytes and C-reactive protein in the patients with COVID-19（P< 0.05）. ②Ofthe 59 confirmed patients, 52 (88.14%) had positive SARS-CoV-2 specific IgM antibody in their serum, while the healthy subjects had negative IgM antibody. In patients with COVID-19, the positive rates of serum SARS-CoV-2 specific IgM antibodies were 25%, 81.82%, 90%, and 100% during the course of 0-6 d, 7-10 d, 11-15 d, 16-20 d, respectively. ③There was no significant difference in the levels of peripheral blood leukocytes, lymphocytes and C-reactive protein between the IgM positive group and the IgM negative group (P>0.05). Conclusion ①After infection with SARS-CoV-2,the leukocyte count in peripheral blood was generally normal or decreased,and some patients presented lymphocytopenia, often accompanied by elevated C-reactive protein.Dynamic observation of the changes of leukocytes, lymphocytes and C-reactive protein is of great significance for the clinical diagnosis and disease observation of COVID-19.②The detection of SARS-CoV-2 specific IgM antibodies in the serum of patients by colloidal gold immunochromatography can be used for auxiliary diagnosis of patients with SARS-CoV-2 infection.

Key words: SARS-CoV-2, COVID-19, Bloodcount, C-reactive protein, IgM antibody