Socioeconomic status at diagnosis influences the incremental direct medical costs of systemic lupus erythematosus: A longitudinal population-based study

Objectives: To assess the incremental direct medical costs of a population-based cohort of incident systemic lupus erythematosus (SLE) for the first five years after diagnosis, and impact of socioeconomic status (SES) on such incremental costs.

Methods: From the administrative health databases in British Columbia, Canada, we identified all adults with newly-diagnosed SLE from 1996 to 2010 and obtained a sample from the general non-SLE population matched on sex, age, and calendar-year. We captured costs for outpatient encounters, hospitalisations, and dispensed medications. Using two-part generalised linear models, we estimated per-person-year incremental costs of SLE (difference in costs between SLE and non-SLE, controlling for covariates) during the first five years after diagnosis, and assessed differences in incremental costs across SES groups.

Results: We included 4679 newly-diagnosed SLE (86% identified from hospitalisations or rheumatologists) and 23,219 non-SLE individuals. Per-person direct costs for SLE in the first year after diagnosis averaged $13,038 (2013 Canadian), with 61% from hospitalisations, 23% from outpatient encounters, and 16% from medications; costs for non-SLE averaged $2,431. Following adjustment, incremental costs of SLE during the first five years after diagnosis averaged $10,078 per-person-year (95% CI=$2062-$32,254). Predicted incremental hospitalisation, outpatient, and medication costs were all significantly-greater for the low-SES patients versus high-SES (additional $1922 per-person-year in incremental costs for low-SES). Similar patterns were observed when restricting to those followed the full five-years after index date.

Conclusion: Even in a single-payer, publicly-funded healthcare setting, low SES at SLE diagnosis was associated with significantly-greater direct medical costs for the management of SLE and associated complications.