Background/Purpose:

We describe the costs associated with damage states in a Canadian-wide SLE cohort using multi-state modeling, which provides a dynamic representation of damage accrual in real time.

Methods:

Patients fulfilling the revised ACR or Systemic Lupus International Collaborating Clinics (SLICC) Classification Criteria for SLE from 6 Canadian centres were enrolled.  Participants completed validated health resource utilization (including hospitalizations, medications, physician visits, tests, and emergency room visits) and lost productivity questionnaires.  Direct costs were calculated by multiplying health resources by their 2017 Canadian prices.  Indirect costs included time loss and impaired productivity in labour force and non-labour force activities and were valued using age-sex specific wages from Statistics Canada.  Annual costs associated with damage states (SLICC/ACR Damage Index [SDI]) were obtained from multiple regressions adjusting for age, race/ethnicity, and disease duration.  To compute long-term estimates of direct/indirect costs, annual costs associated with each level of disease damage were multiplied by the expected duration in each state, forecasted using a multi-state Markov model (Bruce IN. Ann Rheum Dis 2015;74:1706-13).  Future costs were discounted at a yearly rate of 3%.

Results:

1361 patients participated, 90.4% female, 71.0% Caucasian, mean age at diagnosis 33.1 years (SD 13.5), mean SLE duration at completion of economic questionnaire 16.8 years (SD 11.6), mean SLE Disease Activity Index (SLEDAI-2K) 2.71 (SD 3.21), and mean SDI 1.54 (SD 1.87).  Annual direct and total costs were higher in those with an SDI ≥5 (Table 1).

Table 1. Predicted Annual Health Costs Stratified by SDI

Five and 10-year cumulative direct and total costs increased with increasing baseline SDIs, while indirect costs did not differ when stratified by baseline SDI (Table 2).

Table 2.  Predicted 5 and 10- Year Cumulative Costs Stratified by Baseline SDI

Conclusion:

Patients with the highest baseline SDIs incurred cumulative direct costs that were 4.2-fold higher and total costs almost 2-fold higher than those with the lowest baseline SDIs. Indirect costs did not vary with SDI and patients with no or minimal damage still experienced considerably reduced productivity.  Indirect costs exceeded direct, on average, by 3.9-fold, underscoring the importance of lost workforce productivity, and the need for actionable workplace and systems-level (i.e., government, policies, and society) interventions to improve the employment outcomes of those living with SLE.