Effectiveness of low-dose intravenous immunoglobulin therapy in minor primary antibody deficiencies: a two-year real-life experience

Primary Antibody Deficiencies (PAD) are the most prevalent group of Primary Immunodeficiencies (PID) in adults and Immunoglobulin Replacement Therapy (IRT) is the mainstay therapy to improve clinical outcomes. IRT is, however, expensive and, in minor PAD, clear recommendations about IRT are lacking. We conducted a retrospective real-life study to assess the effectiveness of low-dose IRT in minor PAD on 143 patients fulfilling European Society for Immunodeficiencies (ESID) diagnostic criteria for IgG subclass deficiency (IgGSD) or Unclassified Antibody Deficiency (UAD). All patients were treated with intravenous low-dose IRT (0.14±0.06 g/kg/month). Immunoglobulin (Ig) classes and IgG subclasses were measured at baseline and after one year of IRT. The annual rate of total infections, upper respiratory tract infections (URTI), lower respiratory tract infections (LRTI) and hospitalizations was measured at baseline, after one and after two years of IRT. After one year of IRT significant improvement was demonstrated in: a) serum IgG (787.9±229.3 vs 929.1±206.7 mg/dl; p<0.0001); b) Serum IgG subclasses (IgG1 351.4±109.9 vs 464.3±124.1, p<0.0001; IgG2 259.1±140 vs 330.6±124.9, p<0.0001; IgG3 50.2±26.7 vs 55.6±28.9 mg/dl, p<0.002); c) annual rate of total infections (5.75±3.87 vs 2.13±1.74, p<0.0001), URTI (1.48±3.15 vs 0.69±1.27; p<0.005), LRTI (3.89±3.52 vs 1.29±1.37; p<0.0001) and hospitalizations (0.37±0.77 vs 0.15±0.5; p<0.0002). The improvement persisted after two years of IRT. No significant improvement in URTI annual rate was noted in UAD and in patients with bronchiectasis. In conclusion, low-dose IRT can improve clinical outcomes in UAD and IgGSD patients, providing a potential economical advantage over the standard IRT dose.