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.