Background Little is known about the association of healthcare costs with damage accrual in SLE. We describe the costs associated with damage progression 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 2017 Canadian prices. Annual costs associated with SDI states were obtained from multiple regressions adjusting for age, sex, 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 model and longitudinal SDI data from the SLICC Inception Cohort (Bruce IN et al. Ann Rheum Dis 2015;74: 1706– 13). Future costs were discounted at a yearly rate of 3%.
Results 1676 patients participated, 88.7% female, 49.2% Caucasian, mean age at diagnosis 34.6 years (SD 13.4), mean disease duration at enrollment 0.5 years (range 0–1.3 years), and mean follow up 7.8 years (range 0.6–16.9 years). Health resource utilization and annual costs (after adjustment using regression) were markedly higher in those with higher SDIs (SDI=0, annual costs $1847, 95% CI $1120 to $2574; SDI≥5, annual costs $26 772, 95% CI $19 631 to $33 813). At SDI≤2, hospitalizations and medications accounted for 97.1% of direct costs, whereas at SDI≥3, dialysis was responsible for 55.0%.
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. Five and 10 year costs were greater in those with the highest SDIs at baseline (table 1).
Conclusions Patients with the highest baseline SDIs incur annual costs and 10 year cumulative costs that are at least 10-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.
Acknowledgements The Systemic Lupus International Collaborating Clinics (SLICC) research network received partial funding for this study from UCB Pharmaceuticals.
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