Cost-Minimization Analysis of Anti-D Immune Globulin Versus Intravenous Immune Globulin for the Initial Treatment of Immune Thrombocytopenic Purpura.

Abstract

Immune Thrombocytopenic Purpura (ITP) is an autoimmune disorder in which opsonized platelets are prematurely destroyed within the spleen. At this time both anti-D immune globulin (anti-D) and intravenous immune globulin (IVIG) are established treatment options for the management of ITP in children and adults. Due to the tremendous increase in demand for IVIG products in the past decade and the subsequent lack of sufficient production a national shortage has emerged. As a consequence, the direct cost and resulting burden on the healthcare payer has risen dramatically for this treatment option. We performed a cost-minimization analysis (CMA) to compare the cost of using anti-D versus IVIG for the initial treatment of non emergent ITP in appropriate patients. A CMA was employed for this economic evaluation because clinical evidence supports the supposition that the efficacies of the treatment options in question are similar. The perspective used for this study was that of the healthcare payer. The study population includes children and adults with non emergent forms of ITP who are both Rh positive and nonsplenectomized. This CMA did not include the cost to the healthcare payer for treatment administration or the incidence and cost of subsequent treatments for each product. The incidence of severe adverse events when using IVIG or anti-D are rare and therefore were not included in this CMA. In this analysis the cost for the non emergent initial treatment of ITP using [Immune Globulin Intravenous (Human)] 10% (Gammagard Liquid 10%) 1gm/kg × 2 days was compared to anti-D (WinRho® SDF Liquid) 50μg/kg × 1 day respectively. We performed a CMA using the same initial dose and duration of IVIG and anti-D dosed at 75μg/kg. And finally we performed a CMA using one day of treatment for both IVIG and anti-D dosed at 75μg/kg. An average patient weight of 75kg was used for initial dose calculations for each product. The average wholesale price (AWP) for each product was used for cost calculations. Gammagard Liquid 10% was selected as the product for IVIG therapy because this product currently holds a large portion of market share for IVIG products in the US. An example CMA calculation was; Gammagard Liquid 10% 1g/kg × 75kg × 2 days × $101.25 – WinRho® SDF 50μg/kg × 75kg × $1.10/μg. The results of these three CMAs when using anti-D versus IVIG for the initial treatment of ITP yielded a cost savings of $11,063.00, $9,000.50 and $1,406.25 respectively. When the CMA calculations were adjusted to use the actual number of vials needed to dispense the final dose of IVIG and anti-D dosed at 75μg/kg, the savings realized was $1,213.75 per dose dispensed. These CMAs have demonstrated the cost benefit of using anti-D for the initial treatment of non emergent ITP in appropriate patients.