Upon enrolment,case report forms documenting the participant's previous medical history, IVIG treatments and adverse reactions, and concurrent medication use will be collected. Laboratory testing for hemolysis will be performed at baseline, immediately following the completed high-dose cycle (usually administered over 1-2 days), and then again at 5-10 days post-infusion. IVIG associated. Hemolysis will be defined and graded as per the criteria of the Canadian IVIG Pharmacovigilance Group. The pathophysiology of IVIG-associated hemolysis will be characterized by tracking changes in serum complement levels, performing extended cytokine profiling, and conducting mononuclear phagocyte activity assays using patient monocytes. Secretor gene status, ABO zygosity and FcR polymorphisms will also be determined. A predictive model incorporating both patient factors (eg., blood group, total dose prescribed, presence of pre-infusion inflammation) and product factors (eg., specific lot number) will then be developed.