Construction of a Frailty Index as a Novel Health Measure in Systemic Lupus Erythematosus

Objective. To construct a Frailty Index (FI) as a measure of vulnerability to adverse outcomes among patients with systemic lupus erythematosus (SLE), using data from the Systemic Lupus International Collaborating Clinics (SLICC) inception cohort. Methods. The SLICC inception cohort consists of recently diagnosed patients with SLE followed annually with clinical and laboratory assessments. For this analysis, the baseline visit was defined as the first study visit at which sufficient information was available for construction of an FI. Following a standard procedure, variables from the SLICC database were evaluated as potential health deficits. Selected health deficits were then used to generate a SLICC-FI. The prevalence of frailty in the baseline dataset was evaluated using established cutpoints for FI values. Results. The 1683 patients with SLE (92.1% of the overall cohort) eligible for inclusion in the baseline dataset were mostly female (89%) with mean (SD) age 35.7 (13.4) years and mean (SD) disease duration 18.8 (15.7) months at baseline. Of 222 variables, 48 met criteria for inclusion in the SLICC-FI. Mean (SD) SLICC-FI was 0.17 (0.08) with a range from 0 to 0.51. At baseline, 27.1% (95% CI 25.0-29.2) of patients were classified as frail, based on SLICC-FI values > 0.21. Conclusion. The SLICC inception cohort permits feasible construction of an FI for use in patients with SLE. Even in a relatively young cohort of patients with SLE, frailty was common. The SLICC-FI may be a useful tool for identifying patients with SLE who are most vulnerable to adverse outcomes, but validation of this index is required prior to its use.