Economic Evaluation of Damage Accrual in the Systemic Lupus International Collaborating Clinics (SLICC) Inception Cohort

Abstract

Background/Purpose:

Little is known about the association of healthcare costs and damage accrual. We describe the costs associated with damage progression using multi-state modeling.

Methods:

Patients fulfilling the revised ACR Criteria for SLE from 32 centres in 11 countries were enrolled in the SLICC Inception Cohort within 15 months of diagnosis. To supplement the primary data collection, patients were sampled cross-sectionally at a single time between 4 and 17 years of disease duration on healthcare use and lost labour force/non-labour force productivity over the preceding year. Healthcare use was costed using 2017 Canadian prices (direct costs) and lost productivity using 2017 Statistics Canada age-sex specific wages (indirect costs). Annual costs associated with damage states (SLICC/ACR Damage Index [SDI]) were estimated from multiple regressions adjusting for age, sex, race/ethnicity, and disease duration. Five and 10-year cumulative costs were estimated by multiplying annual costs associated with each SDI state by the expected duration in each state, forecasted using a multi-state model and longitudinal SDI data from the SLICC Inception Cohort (Bruce IN. Ann Rheum Dis 2015;74:1706-13). Future costs were discounted at a yearly rate of 3%.

Results:

457 patients participated, 88.2% female, 44.6% Caucasian, mean age at diagnosis 33.6 years, mean disease duration at time of the economic data 10.0 years, mean SLE Disease Activity Index (SLEDAI-2K) 2.97, and mean SDI 1.07. Annual direct costs were higher in those with an SDI ≥5 (Table 1). At SDI ≥2, hospitalizations and medications accounted for 54.3% of direct costs, whereas at SDI ≥3, dialysis was responsible for 55.6%.

Conclusion:

Patients with the highest baseline SDIs incurred cumulative 5 and 10-year direct costs approximately 4-fold higher than those with the lowest SDIs. However, indirect costs were influenced by factors other than SDI (potentially disease activity, quality of life, fatigue, plateauing of expectations regarding productivity later in the disease) and patients incurred considerable indirect costs even with no or minimal damage. This work demonstrates the substantial increase in direct costs in patients with higher damage, highlighting the cost savings potentially achieved by earlier introduction of therapies more effective at attenuating damage progression.