IgG2 as an independent risk factor for mortality in patients with community-acquired pneumonia

Abstract Background Mortality in patients with community-acquired pneumonia (CAP) remains high despite improvements in treatment. Objective To determine immunoglobulin levels in patients with CAP and impact on disease severity and mortality. Methodology Observational study. Hospitalized patients with CAP were followed up for 30 -days. Levels of immunoglobulin G (IgG) and subclasses, immunoglobulin A (IgA) and immunoglobulin M (IgM) were measured in serum within 24 hours of CAP diagnosis. Results 362 patients with CAP were enrolled − 172 ward-treated and 190 ICU-treated. ICU-treated patients had significantly lower values of IgG1, IgG2, IgG3 subclasses and IgA than ward-treated patients. 38 patients died before 30 days. Levels of IgG2 were significantly lower in non-survivors than survivors (P = .004) and IgG2 < 301 mg/dL was associated with poorer survival according to both the bivariate (hazard ratio 4.47; P < .001) and multivariate (HR 3.48; P = .003) analyses. Conclusions Patients with CAP with IgG2 levels < 301 mg/dL had a poorer prognosis and a higher risk of death. Our study suggests the usefulness of IgG2 to predict CAP evolution and to provide support measures or additional treatment.