Immunoglobulin Dosage and Switch from Intravenous to Subcutaneous Immunoglobulin Replacement Therapy in Patients with Primary Hypogammaglobulinemia: Decreasing Dosage Does Not Alter Serum IgG Levels

The impact of reducing immunoglobulin dosage while switching from intravenous to subcutaneous replacement therapy was evaluated. Sixty-five patients with primary hypogammaglobulinemia on stable intravenous replacement therapy were included in a monocentric longitudinal trial. IgG trough levels were measured at baseline and during 1 year following the switch to the subcutaneous route. Mean IgG trough level after 12 months of subcutaneous therapy was increased by 5.4% (8.37-8.82 g/l, p = 0.3), while immunoglobulin dosage had been reduced by 28.3% (151-108 mg/kg/week, p < 0.0001). For the patients with the lowest serum IgG level upon intravenous infusions, serum IgG level rose by 37% (5.33-7.33 g/l, p = 0.003), while mean immunoglobulin dosage was reduced by 36% (170-109 mg/kg/week, p = 0.04). The present study shows that sustained serum IgG levels can be achieved after switching towards subcutaneous replacement despite using reduced immunoglobulin doses.