Performance of urea-mediated dissociation in reducing false-positive of 2019-nCoV IgM test / 中华检验医学杂志

ABSTRACT

Objective:To investigate the interference factors causing false-positive result of novel coronavirus IgM antibody detected by gold immunochromatography assay (GICA) and enzyme-linked immunosorbent assay (ELISA).Methods:A total of 71 serum from different pathogen infections and related chronic diseases patients were collected from the Affiliated Hospital of North Sichuan Medical College from January 22, 2020 to February 15, 2020. GICA and ELISA were used to detect 2019-nCoV IgM in 71 serum, including 5 influenza A virus (Flu A) IgM positive serum, 5 influenza B virus (Flu B) IgM positive serum, 5 Mycoplasma pneumonia (MP) IgM positive serum, 5 Legionella pneumophila (LP) IgM positive serum, 29 rheumatoid factor (RF) IgM positive serum, 5 hypertension patients serum, 5 diabetes mellitus patients serum, 6 human immunodeficiency virus (HIV) infection patients serum and 6 COVID-19 patients serum. The interference factors causing false positive results of the two methods were analyzed, and urea dissociation test was employed to dissociate the 2019-nCoV IgM positive serum using the best dissociation concentration. Statistical analyses were performed by SPSS, version 19.0.Results:2019-nCoV IgM was positive in 18 cases of middle-high level RF-IgM positive serum and 6 cases of 2019-nCoV-infected serum detected by two methods, and the other 47 serum were negative. When the dissociation concentration of urea was 6 mol/L, 2019-nCoV IgM was negative in 17 cases of middle-high level RF-IgM positive serum and positive in 6 cases of 2019-nCoV-infected serum detected by GICA. When the urea dissociation concentration was 4 mol/L, dissociation time was 10 min and the avidity index<0.46 was set as negative, 2019-nCoV IgM was negative in 15 cases of middle-high level RF-IgM positive serum and positive in 6 cases of 2019-nCoV-infected serum detected by ELISA.Conclusion:The middle-high level of RF-IgM could cause false positive results of 2019-nCoV IgM detected by GICA and ELISA, and the urea dissociation test would be helpful for reducing the probability of false-positive results of 2019-nCoV IgM test.