Clinical significance of serum immunoglobulin G subclass deficiency in patients with chronic lymphocytic leukemia.

BACKGROUND: Patients with chronic lymphocytic leukemia (CLL) and hypogammaglobulinemia who suffer from recurrent infections can be offered prophylactic intravenous immunoglobulin (Ig) substitution. Our aim was to assess the prevalence of pure IgG subclass deficiency (with normal Ig levels), its correlation to risk of infection, and the clinical value of routine measurement of serum IgG subclass levels in patients with CLL.
METHODS: Serum levels of Ig and IgG subclasses were determined in patients with CLL at Uppsala University Hospital. Clinical data were collected through patient records and questionnaires.
RESULTS: Hypogammaglobulinemia occurred in 52.3% out of 111 patients. These patients did not have a higher annual risk of infection than patients without hypogammaglobulinemia (79.5% vs 79.1%, p = 0.706 for all infections; 13.4% vs 11.2%, p = 0.394 for severe infection; and 1.7% vs 3.4%, p = 0.083 for sepsis). Pure subclass deficiency was uncommon and occurred in 6 patients (5.4%). The annual overall risk of infection, of severe infection, and of sepsis for these patients did not differ as compared to patients with no hypogammaglobulinemia and no subclass deficiency (70.8% vs 80.7%, p = 0.334; 11.8% vs 11.1%, p = 0.497; and 8.9% vs 2.3%, p = 0.067, respectively).
CONCLUSIONS: Pure IgG subclass deficiency is rare in patients with CLL. In this heterogeneous cohort of patients, neither hypogammaglobulinemia nor pure IgG subclass deficiency were significant risk factors for infectious complications. Measurement of serum levels of Ig may be justified in patients with recurrent severe infections, but routine analysis of IgG subclass levels in patients with CLL is probably not warranted.