Immunoglobulin treatment and clinical outcomes: data from the Ontario Immunoglobulin Treatment program multicenter case registry.

Background: The therapeutic use of immunoglobulin (IG) is increasing and accounts for the largest expenditure in the Canadian Blood Services budget. However, more granular data on IG utilization is limited. Objective: To describe IG treatment indications, dosing characteristics, and clinical outcomes in patients enrolled in the Ontario IG Treatment (ONIT) program, a government-funded pilot clinical program with a case registry. Methods: A longitudinal descriptive study was conducted on ONIT registry participants from June 1, 2020 to March 31, 2024. Results: Six hundred ninety-three consenting participants were included; 429 (61.9%) were female; median [Q1, Q3] age was 62 [47, 71] years; 47 (6.8%) passed away during the study period. Of 693, 658 (94.9%) were receiving IG treatment: 544 (82.7%) on SCIG and 114 (17.3%) on IVIG. Treatment indications were primary immune deficiency (PID) (299, 43.1%), secondary immune deficiency (SID) (348, 50.2%), and immune-mediated disease (IMD) (46, 6.7%). The median dose was 0.48 [0.42, 0.57] and 0.52 [0.44, 0.64] g/kg/4 weeks, for SCIG and IVIG, respectively. Seventy-three patients transitioned from IVIG to SCIG, with the dose adjusted to clinical response. The IVIG:SCIG conversion ratios were 1:1, 1:0.9, and 1:1.2 for PID, SID, and IMD, respectively. Only 33 (5.0%) stopped IG during the study. There was a 78.4% reduction in infections and over 90% reduction in emergency room visits and hospitalizations in PID and SID. Most patients (89.4%) reported improved health after starting IG therapy. Conclusion: The study provides insights into the current landscape of IG utilization, which may inform health system research and support healthcare delivery planning.