IVIG (Intravenous Immunoglobulin) and SCIG (Subcutaneous Immunoglobulin) have been regarded as therapeutically equivalent treatments for primary immunodeficiency diseases (PIDDs). IgG trough level is used as a monitoring measure for infection prevention. A systematic review and meta-analysis was performed in patients with PIDD and relationship between IgG dosing, trough IgG levels with overall infection incidence were evaluated.
Medline, EMBASE, Cochrane, Central and Scopus were searched for studies published from Jan 2000- June 2018, fulfilling the inclusion criteria. DerSimonian and Laird random-effect method was used to pool difference of IgG trough levels. Random-effect meta-regression was used to evaluate infection incidence per 100 mg/dl IgG trough increase through IVIG and SCIG.
Out of 24 observational studies included (1,426 patients), 11 compared IgG trough levels among SCIG and IVIG (mean difference: 73.4 mg/dl, 95% CI: 31.67-119.19 mg/dl, I2= 45%, p=0.05), favoring SCIG. For every 100 mg/dl increase in trough, a linear trend of decreased incidence rates of infection was identified in SCIG patients (p=0.03), but no similar trend was identified in trough levels vs. infection rates for patients receiving IVIG (p=0.67).
SCIG is associated with a higher IgG trough level in comparison to IVIG. Higher SCIG troughs were associated with lower infection rates, while IVIG troughs demonstrated no relationship.