Background Giant cell arteritis (GCA), a chronic vasculitis commonly presenting with headache due to involvement of the temporal arteries, affects approximately 230,000 individuals in the United States (US). However, limited data exist on the health care resource utilization and costs that are attributable to GCA.

Objectives The objective of this study was to estimate the cost of illness in patients with GCA in the US.

Methods A retrospective cohort of patients with incident GCA and five matched controls was identified from a large US claims database between January 1st 2008 and December 31st 2011. GCA patient status was defined by a diagnosis of GCA (ICD-9 446.5), no GCA diagnosis in the 12-months prior, and age greater or equal to 50 years at the time of diagnosis. To create the control group of matched patients without GCA, patients without GCA were randomly assigned an index event month within a calendar year. GCA patients and controls were matched on age, gender, U.S. region, index year of diagnosis, and index month of diagnosis. Only individuals continuously enrolled for 12 months before and 12 months after the index GCA diagnosis (for GCA patients) or the randomly-assigned index date (for controls) were included. One-year costs of healthcare (pharmacy, outpatient, inpatient, and total) among GCA patients and controls were compared, adjusting for age, gender, Charlson Comorbidity Index (CCI), Chronic Condition Count (CCC), U.S. region, and health plan type (HMO vs. other) using generalized linear models. A log link and gamma family was used to model costs, and recycled prediction to calculate cost differences.

Results A cohort of 11,245 GCA patients and 56,230 controls was identified. The mean age of the cohort was 70 years and 71% were females. Mean CCI was 1.6 for GCA patients and 0.8 for controls. Mean CCC was 11.0 for GCA patients and 4.9 for controls. When compared to control patients, GCA patients had higher mean one-year unadjusted pharmacy costs ($3,200, SD $5,700 vs. $2,860, SD $5,300), outpatient costs ($15,000; SD 28,600 vs. $5,860, SD 20,900), inpatient costs ($8,100, SD $29,800 vs. $2,830, SD $14,800), and total costs ($26,400, SD $48,500 vs. $11,500, SD $29,200). After multivariate adjustment, mean one-year cost for GCA patients were lower for pharmacy costs ($-815, 95% CI: $-990–$-640) but higher for outpatient costs ($3,780; 95% CI: $3,350–$4,200) and inpatient costs ($1,500; 95% CI: $1,150–$4,200). Mean adjusted one-year total costs were also higher for GCA patients compared to controls ($4,800; 95% CI: $4,090–$5,520).

Conclusions Patients with GCA experience increased healthcare costs compared to patients without GCA after adjusting for covariates related to health care utilization and costs. Our results are the first to inform researchers, clinicians, and policymakers on the cost burden of GCA, estimated to be approximately $1 billion annually in the US. The results may provide guidance for future research and resource allocation decisions.

References

1. Lawrence, R.C., et al., Estimates of the prevalence of arthritis and other rheumatic conditions in the United States. Part II. Arthritis Rheum, 2008. 58(1): p. 26-35.

Acknowledgements The study was funded through an unrestricted research grant to the University of Washington from Genentech Inc.

Disclosure of Interest J. Babigumira Grant/research support from: Genentech Inc, M. Li Grant/research support from: Genentech Inc, D. Boudreau Grant/research support from: Genentech Inc, J. Best Employee of: Genentech Inc, L. Garrison Grant/research support from: Genentech Inc