A Method To Prevent SARS-CoV-2 IgM False Positives in Gold Immunochromatography and Enzyme-Linked Immunosorbent Assays

• Published in: Journal of clinical microbiology 2020-05, Vol.58 (6)
• Main Authors: Wang, Qiang, Du, Qin, Guo, Bin, Mu, Daiyong, Lu, Xiaolan, Ma, Qiang, Guo, Yangliu, Fang, Li, Zhang, Bing, Zhang, Guoyuan, Guo, Xiaolan
• Format: Article
• Language: English
• Subjects: Betacoronavirus - immunology; Chromatography, Affinity - methods; Clinical Laboratory Techniques - methods; Coronavirus Infections - diagnosis; COVID-19; COVID-19 Testing; Enzyme-Linked Immunosorbent Assay - methods; False Positive Reactions; Humans; Immunoassays; Immunoglobulin M - blood; Pandemics; Pneumonia, Viral - diagnosis; SARS-CoV-2
• ISSN: 0095-1137; 1098-660X
• DOI: 10.1128/jcm.00375-20

We set out to investigate the interference factors that led to false-positive novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) IgM detection results using gold immunochromatography assay (GICA) and enzyme-linked immunosorbent assay (ELISA) and the corresponding solutions. GICA and ELISA were used to detect SARS-CoV-2 IgM in 86 serum samples, including 5 influenza A virus (Flu A) IgM-positive sera, 5 influenza B virus (Flu B) IgM-positive sera, 5 IgM-positive sera, 5 IgM-positive sera, 6 sera of HIV infection patients, 36 rheumatoid factor IgM (RF-IgM)-positive sera, 5 sera from hypertensive patients, 5 sera from diabetes mellitus patients, and 14 sera from novel coronavirus infection disease 19 (COVID-19) patients. The interference factors causing false-positive reactivity with the two methods were analyzed, and the urea dissociation test was employed to dissociate the SARS-CoV-2 IgM-positive serum using the best dissociation concentration. The two methods detected positive SARS-CoV-2 IgM in 22 mid-to-high-level-RF-IgM-positive sera and 14 sera from COVID-19 patients; the other 50 sera were negative. At a urea dissociation concentration of 6 mol/liter, SARS-CoV-2 IgM results were positive in 1 mid-to-high-level-RF-IgM-positive serum and in 14 COVID-19 patient sera detected using GICA. At a urea dissociation concentration of 4 mol/liter and with affinity index (AI) levels lower than 0.371 set to negative, SARS-CoV-2 IgM results were positive in 3 mid-to-high-level-RF-IgM-positive sera and in 14 COVID-19 patient sera detected using ELISA. The presence of RF-IgM at mid-to-high levels could lead to false-positive reactivity of SARS-CoV-2 IgM detected using GICA and ELISA, and urea dissociation tests would be helpful in reducing SARS-CoV-2 IgM false-positive results.