Serial Serum Immunoglobulin G (IgG) Trough Levels in Patients with X-linked Agammaglobulinemia on Replacement Therapy with Intravenous Immunoglobulin: Its Correlation with Infections in Indian Children

Patients with primary antibody deficiency (PAD) are being increasingly diagnosed in the developing world. However, care of these children continues to remain suboptimal due to financial and social constraints. Immunoglobulin (Ig) trough level is an important predicting factor for infections in children on replacement immunoglobulin therapy. There are no data on this aspect from the developing world. Therefore, we studied serial immunoglobulin G (IgG) trough levels in 14 children with X-linked agammaglobulinemia (XLA) receiving replacement intravenous immunoglobulin (IVIG). Infections during the course of enrolment were documented prospectively. Mean age at the time of diagnosis was 5.1 years (range 2–11 years). Mean time from onset of symptoms and initiation of therapy was 3.3 years. Two children had established chronic lung disease prior to enrolment. Total numbers of major and minor infections were 7 and 40, respectively. At a mean dose of 414 mg/kg/month of IVIG, mean trough IgG level was 435 mg/dl. Median IgG trough levels during the episodes of major and minor infections were 244 and 335 mg/dl, respectively. An escalation in IVIG dose of 100 mg/kg produced an increase in serum IgG levels by 53.6 mg/dl. Median trough IgG level of 354 mg/dl was found to be protective with 64% sensitivity and 75% specificity. A median dose of 397 mg/kg was required to keep children free of infections. Despite financial constraints and several challenges in the context of a developing country, children with XLA have good outcome on replacement immunoglobulin therapy. Furthermore, mean biological trough IgG levels are much lower than reported in for Western patients; however, studies involving larger number of subjects are required in future to draw firm conclusions.