Objective: In a large group of patients with primary immunodeficiency (PID), immunoglobulin replacement therapy is critical for infection control. There are two main methods of immunoglobulin replacement intravenous (IVIG) and subcutaneous (SCIG). The aim of this study was to determine the efficacy of SCIG by comparing IgG levels and frequency of infections obtained during SCIG replacements in patients with PID with those obtained during IVIG administration.

Method: Immunoglobulin levels of 28 patients who were followed up in our clinic with a diagnosis of PID and who started IVIG replacement and switched to SCIG replacement after follow-up, were evaluated retrospectively. Serum IgG levels and frequency of infections before starting immunoglobulin treatment, the previous year of IVIG before starting SCIG replacement, and during the first six months, second six months, and second year of SCIG replacement were compared.

Results: The mean age of all the patients that received SCIG was 10.5 years (min 15 months, max 23 years) and eleven of the patients were female. The mean serum IgG level of the patients before starting immunoglobulin replacement was 701±383 mg/dl, and for the final year they received IVIG replacement before switching to SCIG replacement it was calculated to be 900±342 mg/dl. The mean value was found to be 1082±312 mg/dl in the first six months after the initiation of SCIG, 1102±287 mg/dl in the second six months, and 1145±311 mg/dl in the second year. Serum IgG levels of the patients were significantly higher during IVIG and SCIG replacement than before treatment (p<0.05). Serum IgG levels during the first six months, second six months, and second year of SCIG treatment were significantly higher than levels during IVIG treatment (p=0.000, p=0.003, and p=0.002, respectively).

Conclusion: Compared to IVIG replacement, significantly higher and more stable serum IgG levels can be obtained with SCIG replacement. This is expected to ensure improved outcomes in the management of infections in PID patients.

Keywords: IgG levels, intravenous immunoglobulin replacement, subcutaneous immunoglobulin replacement