SLE Frailty Index Feasible for Measuring Adverse Outcome Susceptibility

Construction of a frailty index for patients with systemic lupus erythematosus (SLE) was feasible as a valid and reliable measure of adverse outcome susceptibility, and a high frailty prevalence was noted among members of the Systemic Lupus International Collaborating Clinics (SLICC) inception cohort, according to a study published in The Journal of Rheumatology.

Determining vulnerability to adverse outcomes through frailty measurements would help clinicians assess risk levels in a clinically variable patient population, but a deficit accumulation approach has not been attempted for SLE. Use of a frailty index in SLE could improve comprehension of the diverse outcomes seen with this disease. Investigators sought to evaluate the construction and use of a frailty index as a novel health index for individuals diagnosed with SLE.

A SLICC cohort secondary analysis enrolled 1683 participants (92.1% of entire cohort; mean age, 35.7 years; 88.7% women; mean disease duration at baseline, 18.8 months) who were recently diagnosed with SLE and for whom complete data were available. Patients were assessed at baseline (defined as the first visit with information available for frailty index construction) and followed annually with physical examinations and laboratory measurements (including anti-double stranded DNA, complement, creatinine, erythrocyte sedimentation rate, and C-reactive protein). Disease activity was measured by the SLE Disease Activity Index 2000, organ damage was measured by the SLICC/American College of Rheumatology Damage Index, and quality of life was measured by the Medical Outcomes Survey Short-Form 36.

First, researchers evaluated SLICC database variables as potential health deficits and identified suitable candidates. Next, those deficits selected for inclusion were used to create a SLICC frailty index (SLICC-FI), where individual deficits were scored 0 to 1 and the SLICC-FI was calculated as the mean 0 to 1 score across variables. A SLICC-FI score >0.21 was set as the cutoff for frailty.

From a total of 222 identified candidate health deficit variables, 48 were included in the SLICC-FI. Scores ranged from 0 to 0.51, with a mean SLICC-FI of 0.17 and a median of 0.16. Analysis revealed that 27.1% (95% CI, 25.0%-29.2%) of participants could be categorized as frail at baseline, which is considerably greater than the frailty rate in the general population. Frailty prevalence rose with increasing age, and compared with those who had the lowest frailty index scores (≤.010), patients classified as frail (>0.21) tended to be less educated, older, and current smokers. Disease duration was generally shorter among frail individuals vs relatively fit patients. Compared with men (23.7%; 95% CI, 17.8%-30.4%), women in the cohort (27.5%; 95% CI, 25.3%-29.9%) demonstrated a trend toward higher frailty prevalence.

Study strengths included use of a standard protocol for health deficit recognition, stable and reliable frailty estimates, and deficit coverage of multiple organ systems across fixed and reversible domains.

Study limitations included a small sample size, inability to calculate SLICC-FI for all patients at enrollment, use of general population frailty index cutoffs, and possible non-generalizability to older patients with SLE with longer disease durations.

“The SLICC-FI may be a useful tool for identifying SLE patients who are most vulnerable to adverse outcomes but validation of this index is required prior to its use,” noted the authors.

Reference

Legge A, Kirkland S, Rockwood K, et al. Construction of a frailty index as a novel health measure in systemic lupus erythematosus [published online April 15, 2019]. J Rheumatol. doi:10.3899/jrheum.181338