Economic Evaluation of Damage Accrual in an International SLE Inception Cohort

초록

Background/Purpose: Little is known about the association of healthcare costs with damage accrual in SLE. We describe the costs associated with damage states across the disease course using multi-state modeling. Methods: Patients fulfilling the revised ACR classification criteria for SLE from 32 centres in 11 countries were enrolled in the Systemic Lupus International Collaborating Clinics (SLICC) inception cohort within 15 months of diagnosis. Annual data on demographics, SLE disease activity (SLEDAI-2K), damage (SLICC/ACR Damage Index [SDI] if ≥ 6 months from diagnosis), hospitalizations, medications, dialysis, and utilization of selected medical/surgical procedures were collected. Annual health resource utilization was costed using 2015 Canadian prices. Annual costs associated with SDI states were obtained from multiple regressions adjusting for age, race/ethnicity, and disease duration. As there were relatively few transitions to SDI states 5 – 11, these were merged into a single SDI state. Five and 10-year cumulative costs were estimated by multiplying annual costs associated with each SDI state by the expected duration in each state, which was forecasted using a multi-state Markov model (Bruce IN et al. Ann Rheum Dis 2015;74:1706-13). Results: 1641 patients participated, 89.2% female, 48.9% Caucasian, mean age at diagnosis 35.2 years (SD 13.4), mean disease duration at enrollment 0.5 years (SD 0.3), and mean follow up 6.1 years (range 0.1 – 13.7 years). Health resource utilization and annual costs (after adjustment using regression) were markedly higher in those with higher SDIs (Table 1). Five and 10-year cumulative costs stratified by baseline SDI were calculated by multiplying the annual costs associated with each SDI by the expected duration in that state (5-year example in Table 2). Five and 10-year costs were greater in those with the highest SDIs at baseline (Table 3). Conclusion: Patients with the highest baseline SDIs incur annual costs and 10-year cumulative costs that are approximately 20-fold higher than those with the lowest baseline SDI. By estimating the expected duration in each SDI state and incorporating annual costs, disease severity at presentation can be used to predict future healthcare costs, critical knowledge for cost-effectiveness evaluations of novel therapies.