Elevated serum IgM levels indicate poor outcome in patients with coronavirus disease 2019 pneumonia: A retrospective case-control study

BackgroundThe coronavirus disease 2019 (COVID-19) pneumonia outbreak began in Wuhan and pandemics tend to occur. Although SARS-CoV-2-specific immunoglobulins have been detected in serum of COVID-19 patients, their dynamics and association with outcomes have not been characterized. MethodsA total of 116 hospitalized patients with confirmed COVID-19 pneumonia and SARS-CoV-2-specific immunoglobulins tested in Tongji hospital were retrospectively investigated. Clinical, laboratory, radiological characteristics and outcomes data were compared between mild-moderate group and died group. Further, a paired case-control study was conducted where each deceased case was matched to three mild-moderate patients of similar age. FindingsAmong 116 subjects included, 101 mild-moderate patients survived and 15 cases died. SARS-CoV-2-specific IgM levels peaked in forth week after onset of COVID-19 pneumonia, while serum IgG levels increased over 8 weeks. Serum IgM levels were higher in deceased patients than mild-moderate patients (P = 0.024), but not IgG. Serum IgM levels were negatively correlated with clinical outcome, eosinophil count and albumin levels (r = -0.269, P = 0.003; r = -0.188, P = 0.043; and r = -0.198, P = 0.033, resp.). The area under the ROC curve (AUC) for IgM antibody was 0.681 (95% CI: 0.517-0.845, P = 0.024). In case-control study paired by age, serum IgM was higher in deceased patients than mild-moderate patients (P = 0.019), positively correlated with leucocyte count (r = 0.260, P = 0.045), while negatively correlated with clinical outcome and albumin levels (r = -0.337, P = 0.008; r = -0.265, P = 0.041). AUC for IgM levels was 0.704 (95% CI: 0.534-0.873, P = 0.019). InterpretationThese results indicate that dynamics of SARS-CoV-2 specific IgM and IgG antibodies was similar with that of SARS-CoV, while elevated serum IgM levels indicate poor outcome in patients with COVID-19 pneumonia.