Arthritis Care & Research · Mar 9, 2026

Developing and Evaluating a Laboratory-Based Frailty Index for the Prediction of Long-Term Health Outcomes in Systemic Lupus Erythematosus

By Burns G, Searle SD, Legge A

OBJECTIVE: We aimed to construct and evaluate the first laboratory-based frailty index (FI-Lab) for predicting adverse outcomes in systemic lupus erythematosus (SLE) and to compare its predictive ability to that of an existing clinical FI. METHODS: We used data from a single-center prospective cohort of adult patients with SLE whose baseline visit occurred between 2010 and 2019. A 30-item FI-Lab was constructed by adapting an existing list of FI-Lab variables. Cox proportional hazards regression examined the association between baseline FI-Lab scores and all-cause mortality, whereas negative binomial regression evaluated the association with organ damage accrual. We compared the performance of multivariable models containing the FI-Lab and/or Systemic Lupus International Collaborating Clinics FI as predictor variables using Akaike information criterion, Harrell's C-statistic, and pseudo-R² values. RESULTS: Among 283 patients (89% women, mean age 47.7 years), 97 were classified as frail at baseline (FI-Lab >0.21). Frail individuals had increased mortality risk (hazard ratio 3.71, 95% confidence interval [CI] 1.82-7.54) and a higher rate of organ damage accrual during follow-up (incidence rate ratio 2.26; 95% CI 1.59-3.22) compared to nonfrail patients. The FI-Lab remained significantly associated with mortality risk after multivariable adjustment. Although both indices were significant baseline predictors of organ damage accrual during follow-up, the multivariable model containing both FIs outperformed models containing either index alone. CONCLUSION: An FI constructed exclusively from routinely collected laboratory variables can measure frailty and predict adverse outcomes in SLE. It may serve as a convenient screening tool to detect subclinical frailty and promote early risk mitigation in this population.

doi.org/10.1002/acr.80036 Open access PubMed 41801062 Biomarkers