Using the Short Form 6D, as an overall measure of health, to predict damage accrual and mortality in patients with systemic lupus erythematosus: XLVII, results from a multiethnic US cohort

Abstract

To determine if overall health status as assessed by the Short Form 6D (SF-6D) index, a preference-based generic measure of health, is associated with the occurrence of damage accrual and mortality in patients with systemic lupus erythematosus (SLE). We studied SLE patients (American College of Rheumatology criteria) from the LUpus in MInorities, NAture versus nurture cohort (LUMINA), a longitudinal multiethnic cohort. The contribution of the SF-6D as assessed at enrollment to damage accrual at the last visit and mortality was examined. All variables previously shown to be determinants of damage accrual and mortality and corroborated by univariable analyses were adjusted for in multivariable models (Poisson and Cox proportional hazards regressions, respectively). Damage accrual and mortality were the dependent variables. Similar analyses were performed examining the associations of the Short Form 36 summary measures (physical component summary [PCS], mental component summary [MCS]) with these outcomes. In 552 patients, the SF-6D was negatively associated with damage accrual and mortality in the univariable analyses; the association with damage was confirmed in the multivariable analyses (chi(2) = 9.020, P = 0.002) but the association with mortality was not confirmed (hazard ratio 0.495, 95% confidence interval 0.041-6.038). When the PCS and MCS were evaluated, the PCS, but not the MCS, was found to be associated with damage but not with mortality. The SF-6D (and the PCS) as measured early in the disease course were found to independently predict damage accrual at the last visit, but not mortality. Although the SF-6D was originally conceived as a utility measure, it may be used to accurately assess overall health status in patients with SLE.