Demonstration of IgG subclass (IgG1 and IgG3) in patients with positive direct antiglobulin tests

Serologic characterization of autoantibodies helps in the management and monitoring of the course of autoimmune hemolytic anemia (AIHA). The purpose of this study was to evaluate gel centrifugation test (GCT) cards for immunoglobulin G (IgG) titer and determination of IgG subclasses IgG1 and IgG3 and their influence on hemolysis. Eighty direct antiglobulin test (DAT)-positive patients were examined with the help of GCT cards for IgG titer and IgG subclasses. The results were correlated with the presence and absence of hemolysis. A statistically significant (p < 0.005) association of hemolysis with increasing anti-IgG titer was observed. When IgG titer was 30 or less, 28 (50.91%) patients had no hemolysis, whereas 15 (93.75%) patients had features of hemolysis when titer was at least 300. Statistically significant (p < 0.005) association of subclass of IgG (IgG1, IgG3) coating the red blood cells with intravascular hemolysis was also seen. Twenty-nine (80.56%) patients had evidence of hemolysis when IgG1 or IgGl-IgG3 both were present. Gel technology is helpful to demonstrate red blood cell-bound autoantibodies and their characterization with regard to class, subclass, and titer. This information is useful to identify patients with AIHA who are at risk of severe hemolysis with adverse prognosis.