Endogenous IgG Hypogammaglobulinaemia in Critically Ill Adults with Sepsis: Systematic Review and Meta-analysis

Purpose: Plasma immunoglobulin concentrations are acutely altered in critically ill patients with sepsis. However, the association between immunoglobulin levels on the day of sepsis diagnosis and subsequent mortality is inconsistent.

Methods: Systematic review of studies that report immunoglobulin measurements and mortality among adults with sepsis managed in a critical care setting. Fixed and random effect meta-analyses were conducted using low IgG levels as primary exposure and acute mortality as the primary outcome. Both variables were used as defined in individual studies.

Results: The prevalence of a low immunoglobulin G (IgG) concentration on the day of sepsis diagnosis was variable [58.3% (IQR 38.4-65.5%)]. Three cut-off points (6.1, 6.5 and 8.7 g/L) were used to define the lower limit of IgG concentrations in the included studies. A subnormal IgG level on the day of sepsis diagnosis was not associated with an increased risk of death in adult patients with severe sepsis and/or septic shock by both fixed and random effect meta-analysis (OR [95% CI] 1.32 [0.93-1.87] and 1.48 [0.78-2.81], respectively).

Conclusions: This systematic review identifies studies of limited quality reporting heterogeneous sepsis cohorts with varying lower limits of normal for IgG. Although our data suggest that a subnormal IgG measurement on the day of sepsis diagnosis does not identify a subgroup of patients with a higher risk of death, further studies are needed to confirm or refute this finding, and whether optimal cut-offs and time windows can be defined for IgG measurement. This would determine whether patients receiving intravenous immunoglobulin therapy for sepsis could be stratified using IgG levels.