Serum IgG levels and mortality in patients with severe sepsis and septic shock : The SBITS data

Abstract

Background: The role of intravenous immune globulin (Ig) therapy in patients with severe sepsis and septic shock is discussed controversially. Low initial IgG levels could help to identify those patients who might benefit from an adjunctive Ig treatment.

Objectives: To investigate the effect of initial serum IgG levels on 28-day mortality in patients with severe sepsis and septic shock.

Materials and methods: In this retrospective analysis of the SBITS trial data, 543 patients were allocated to four groups (quartiles) depending on their initial serum IgG levels (1: IgG ≤ 6.1 g/l; 2: IgG 6.2-8.4 g/l; 3: IgG 8.5-11.9 g/l; 4: IgG > 11.9 g/l). The third quartile was taken as the reference quartile. For the applied logistic regression model clinically relevant confounders were defined and integrated into further risk-adjusted calculations.

Results: Patients with the lowest IgG levels had a mortality rate similar to those patients with initial IgG levels in the second and third quartile, representing the physiological IgG range in healthy people. Surprisingly, patients with the highest IgG levels even showed a significantly higher mortality in a risk-adjusted calculation compared to the reference quartile (OR 1.69, CI 1.01-2.81, p = 0.05). Subgroup analyses revealed that initial IgG levels were of no prognostic value in patients presenting with vasopressor-dependent septic shock on admission as well as in patients with either gram-positive or gram-negative sepsis.

Conclusions: Initially low IgG levels do not discriminate between survival and nonsurvival in patients with severe sepsis and septic shock. Therefore, low IgG cannot help to identify those patients who might benefit from an adjunctive IgG sepsis therapy. Whether a high initial IgG serum level is an independent mortality risk factor needs to be investigated prospectively.

Keywords: Immunoglobulins; SBITS trial; Sepsis; Septic shock; Serum IgG level.