Real-world Clinical and Economic Burden of Immunoglobulin-G4-related Disease in the United States: A Retrospective Claims-Based Analysis

Immunoglobulin-G4-related disease (IgG4-RD) is a rare recurring fibroinflammatory autoimmune condition that can affect multiple organs. Although it is gaining recognition, few studies have assessed the clinical and economic burden of this disease. This study aimed to characterize patients with IgG4-RD in the United States and describe healthcare resource utilization (HRU) and costs before and after diagnosis. This retrospective cohort study used a validated algorithm to identify commercially insured adult patients with IgG4-RD from health plan claims data obtained from the IQVIA PharMetrics Plus database (January 1, 2011, to June 30, 2022). The index date was defined as the date of the first observed IgG4-RD-related diagnosis. The baseline and study periods were defined as the 12 months before and after diagnosis, respectively. Demographic characteristics were reported on the index date. Clinical characteristics, IgG4-RD-related treatments, and all-cause HRU and healthcare costs (2022 US dollars, payer’s perspective) were reported during the baseline and study periods. A total of 295 patients with IgG4-RD were included in the study. Comorbid burden was substantial, with hypertension (31.5%), hyperlipidemia (22.4%), and type 2 diabetes (17.3%) being the most common comorbidities after diagnosis. Most patients received IgG4-RD-related treatment before (60.3%) and after (87.8%) diagnosis, with prednisone being the most common (71.5% after diagnosis). Pancreatic and biliary involvement each occurred in nearly a third of patients. Annual HRU was high before (mean of 30.4 outpatient [OP] visits; 22.7% with ≥1 inpatient [IP] admission, lasting a mean of 9.0 days) and after diagnosis (mean of 40.7 OP visits; 35.3% with ≥1 IP admission, lasting a mean of 10.6 days). Mean annual healthcare costs were 1.5 times higher after diagnosis ($69,753) than before diagnosis ($45,844), predominantly driven by increased OP and IP costs. Patients with IgG4-RD had a substantial clinical and economic burden, including high rates of glucocorticoid use, HRU, and healthcare costs both before and after diagnosis. This may suggest a need for earlier detection and improved management of this complex condition. This study provides important insights into the high clinical and economic burden observed in IgG4-RD. Future studies are warranted to gain a deeper understanding of the possible impact of management strategies on patient outcomes.