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Real-World Immunoglobulin Dose Adjustments and Impact on Utilization and Costs

Real-world dose adjustments occurred in patients with primary immunodeficiency who switched from intravenous immunoglobulin to subcutaneous immunoglobulin 20%, with resulting implications for payers, patients, and plasma collection and supply.
Published Online: Apr 18,2016
Xiaolan Ye, PhD; Michelle Luo, PhD; Yan Xiong, MS; and Josephine Li-McLeod, RPh, PhD

Objectives: To examine dose adjustments that occurred in the real world when patients with primary immunodeficiency (PI) disease switched from intravenous immunoglobulin (IGIV) to subcutaneous immunoglobulin (IGSC) 20%, and to evaluate the impact on immunoglobulin (Ig) utilization and costs.
Study Design: Retrospective data analysis.
Methods: Pharmacy claims were extracted from 5 specialty pharmacy dispensing databases. Administration routes, when not available, were identified by prescribed brand and dosing frequency. Patients with ≥2 claims for any IGIV who subsequently switched to IGSC 20% were included. The dose adjustment ratio was calculated as the ratio of grams per 30 days of IGSC 20% to IGIV. Wilcoxon signed rank test was used to test the hypothesis that the dose adjustment ratio differed from 1.0. The model was analyzed to estimate the impact of dose adjustment on IgG utilization and cost.
Results: A total of 247 eligible patients were included; the majority (75%) had a dose adjustment ratio >1.0. Mean dose adjustment was 1.42 and the median was 1.30 (P <.0001). Patients switching to IGSC 20% required an incremental 126 g Ig per patient per year (PPPY), an amount equivalent to treating an average patient with PI with IGIV for approximately 3.6 months. This increase in Ig utilization could result in an incremental cost of $19,026 PPPY.
Conclusions: Real-world dose adjustments may increase Ig utilization and costs when patients with PI switch from IGIV to IGSC 20%. These changes may potentially impact the payers’ budget for drug costs and burden the available plasma collection and supply.

Am J Pharm Benefits. 2016;8(2):61-66


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Primary immunodeficiency (PI) diseases are a group of congenital disorders of the adaptive or innate immune system. The resulting immune dysregulation predisposes affected individuals to an increased rate of infection and autoimmune disease.1,2 There are a total of 500,000 estimated cases of PI in the United States and about 50,000 new cases diagnosed annually.3-7 The incidence of PI is increasing, which may in part be due to increased awareness and diagnosis of the condition.8,9

Since the first PI disease was defined in 1952 (X-linked agammaglobulinemia), more than 150 immune disorders have been identified.2,10 Most PIs involve B-cell and/or T-cell defects that lead to some level of antibody loss. For instance, patients with agammaglobulinemia have very low serum immunoglobulin (Ig), whereas patients with severe combined immune deficiency or class switch recombination (formerly called hyper-IgM syndromes) have no functional serum IgG antibodies.

Other PIs are associated with more modest degrees of immunodeficiency, leading to hypogammaglobulinemia or IgG subclass defects with varying degrees of antibody production ability.11 The hallmark of PI disorders is recurrent or unusual infections.4,12 These devastating disorders of PI are often associated with decreased health-related quality of life (HRQoL), increased mortality, and high healthcare resource utilization and cost, particularly when left undiagnosed and untreated.6,13