Low immunoglobulin G level is associated with poor outcomes in patients with sepsis and septic shock.

Background: Despite studies on low immunoglobulin G (IgG) levels in critically ill patients, their association with clinical outcomes in sepsis patients remains disputed. Herein, we determined the association between low IgG levels and clinical outcomes and investigated the 28-day mortality in patients with low IgG levels.

Methods: We retrospectively identified 238 patients whose serum IgG levels were measured upon intensive care unit admission using medical record data collected between January 2013 and August 2018. We extracted data on patient characteristics, severity scores (APACHE II, SOFA score), neutrophil-lymphocyte ratio (NLR), procalcitonin levels, and serum IgG levels and calculated the cut-off value for the IgG level according to the evaluated clinical outcomes. The primary outcome was 28-day mortality.

Results: There were no significant differences in NLR and procalcitonin levels between survivors and non-survivors; serum IgG levels were significantly higher in survivors than in non-survivors (P = 0.004). A serum IgG cut-off value of 670 mg/dL was calculated from receiver operating characteristic curve analysis, and serum IgG levels significantly predicted survival with an area under the curve of 0.63 (95% CI, 0.54-0.72) (P = 0.004). Patients with low IgG levels (<670 mg/dL) had significantly higher mortality rates than those with normal IgG levels (≥670 mg/dL) (P < 0.001).

Conclusion: Our results reveal that low IgG levels (<670 mg/dL) in critically ill patients are associated with poor clinical outcomes related to 28-day mortality. In patients with sepsis, low IgG levels could be a predictor of poor outcome.