Renal damage is the most important predictor of mortality within the damage index: data from LUMINA LXIV, a multiethnic US cohort

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Abstract
Objective. Damage accrual in SLE has been previously shown to be an independent predictor of mortality. We sought to discern which SLICC Damage Index (SDI) domains are the most important predictors of survival in SLE. Methods. SLE patients (ACR criteria), age ⩾16 years, disease duration ⩽5 years at enrolment, of African–American, Hispanic or Caucasian ethnicity were studied. Disease activity was assessed using the SLAM-Revised (SLAM-R) at diagnosis. Damage was ascertained using the SDI at the last visit. The SDI domains associated with time to death (and interaction terms) were examined by univariable and multivariable Cox proportional hazards regression analyses; those significant in the multivariable analyses were added to the final two models (with and without poverty) that included other variables known to be associated with shorter survival. Results. A total of 635 SLE patients were studied of whom 97 (15.3%) have died over a mean (s.d.) total disease duration of 5.7 (3.7) years. Patients were predominantly women [570 (89.8%)]; their mean (s.d.) age was 36.5 (12.6) years; 126 (19.8%) had developed renal damage, 62 (9.3%) cardiovascular, 48 (7.8%) pulmonary and 34 (5.4%) peripheral vascular damage. When excluding poverty from the multivariable model, the renal domain of the SDI was independently associated with a shorter time to death (hazard ratio = 1.65; 95% CI 1.03, 2.66). Conclusions. The renal domain of the damage index is associated with a shorter time to death when poverty, a strong predictor of this outcome, is removed from the model. Preventing renal damage in lupus patients has long-term prognostic implications.