Serum Immunoglobulin Levels as Potential Biomarkers of COVID-19 Pneumonia

Severe Acute Respiratory Coronavirus-2 (SARS-CoV-2) has been known to cause immune dysregulation. However, the association between specific immunoglobulins and clinical characteristics in COVID-19 remains poorly understood. This study investigated the relationship between immunoglobulins and clinical outcomes in adults hospitalized with COVID-19 pneumonia.

A retrospective chart analysis was performed (N=569, December 2020-April 2021). Information on demographics, clinical factors, and total serum immunoglobulin (IgG, IgA, IgM, and IgE) levels were collected (N=60). Clinical outcomes of interest included: symptom duration, comorbidities (Charlson 10-year-estimated-survival (C10YES) and comorbidity index (CCI), vital derangements upon presentation (NEWS-2-score), length of stay (LOS), and mortality. Spearman correlation, chi-square tests and linear regression were conducted.

Serum IgM levels were positive predictors of C10YES (β=0.104, p=0.023) and negative predictors of CCI (β=-0.007, p=0.047). There was an association between higher serum IgG levels and longer LoS (β=7.455, p=0.047). We found no significant associations between immunoglobulins and preadmission symptom duration, medication use, or mortality.

Total IgM was associated with increased survival and decreased comorbidity, and total IgG was associated with length of hospitalization. IgM may predict the body's initial ability to produce humoral immune responses, and IgG may function as a possible signature of chronic antigenic responses and inflammation, associated with comorbidities that increase COVID-19 hospitalization. Evaluating total IgM and IgG as prognostic biomarkers in COVID-19 pneumonia patients may contribute to improved management and clinical outcomes.