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:
Three hundred sixty-two patients with CAP were enrolled − 172 ward-treated and 190 intensive care unit-treated. Intensive care unit–treated patients had significantly lower values of IgG1, IgG2, IgG3 subclasses, and IgA than ward-treated patients. Thirty-eight 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.