2051: Clinical Burden of Illness Among Patients with Immunoglobulin-G4-Related Disease in the United States

Background/Purpose: Immunoglobulin G4-related disease (IgG4-RD) is a multi-organ, immune-mediated condition. Timely treatment is critical, as disease flares often result in increased inflammation and organ damage. Glucocorticoids (GCs) are used as standard first-line treatment, followed by GC-sparing therapies including conventional synthetic disease-modifying antirheumatic drugs (DMARDs, such as azathioprine, mycophenolate mofetil etc.), or biologic DMARD (rituximab). This study describes patient characteristics, treatment patterns, and incidence of flares in patients with IgG4-RD using administrative claims databases in the United States.

Methods: A retrospective cohort study was conducted using 100% Medicare Fee-for-Service (FFS) and Inovalon MORE² Registry^® claims databases. Adults with IgG4-RD were identified using a previously validated algorithm (Wallace et al. ACR Open Rheumatol. 2022) from January 1, 2018 through December 31, 2021 (FFS) and June 30, 2023 (MORE²). Index date was set as the first claim for an algorithm-defined ICD-10 diagnosis code associated with IgG4-RD. Demographics at the index date and comorbidities and medication use in the 12-month pre-index period were assessed. Medication use and claims-based proxy for IgG4-RD flare were evaluated in the ≥12-month post-index follow-up period. Claims-based proxy for flare was defined as: (1) ≥1 claim for an IgG4-RD-associated diagnosis code followed by initiation of IgG4-RD medication, addition of GCs to existing DMARD therapy, or ≥5mg increase in GC prednisone-equivalent daily dose (PEDD); (2) ≥1 claim for ureteral stent; or (3) ≥1 claim for endoscopy and biliary stent (Figure 1).

Results: Overall, 965 patients with IgG4-RD were identified: mean (SD) age 65.7 (14.2) years, 59.2% male, 61.5% white (Table 1). Most patients had health insurance coverage through Medicare FFS program (64.8%). In the pre-index period, hypertension (62.2%), infections (55.9%), and hyperlipidemia (55.1%) were commonly observed. Moreover, 65.4%, 11.7%, and 8.5% received oral or IV GCs, synthetic DMARDs, and rituximab, respectively, during baseline. The mean (SD) duration of the post-index follow-up period was 45.3 (19.5) months. During follow-up, 97.6%, 33.6%, and 35.2% patients received oral or IV GCs, synthetic DMARDs, and rituximab, respectively (Table 2). Among patients with oral GCs (N = 835, 86.5%), the mean (SD) PEDD was 20.8 (12.1) mg. Claims-based proxy for flare was observed in 90.5% of patients during follow-up.

Conclusion: Results showed a significant clinical burden among patients with IgG4-RD during follow-up, characterized by elevated GC use which might potentially increase the risk for GC-related toxicity events, as well as a high risk of disease flares. Study findings highlight the need for therapies that better control disease activity and minimize GC exposure in these patients in the long-term.