Frailty Index that Measures Disease in Lupus

March 8, 2019

Using a frailty index to predict adverse outcomes and mortality in systemic lupus erythematosus proves to be feasible and effective in a study. The test, SLICC-FI, correlated well with existing measures of SLE disease activity, organ damage and HRQoL.

A recent article accepted for publication and provided online by Arthritis & Rheumatology examines the properties and utility of a frailty index in addition to it’s predictive ability with regards to mortality risk in patients with systemic lupus erythematosus (SLE).

Systemic lupus erythematosus has a highly variable course affecting multiple organ systems with fluctuations in disease activity, organ damage, and significant impacts on health-related quality of life (HRQoL). Predicting disease course, disease activity and mortality are of vital importance in SLE.

Currently the Systemic Lupus International Collaborating Clinics (SLICC)/ ACR Damage Index (SDI) provides a consistent predictive tool for poor outcomes including organ damage and mortality. Unfortunately, due to the complex interplay between organ damage, HRQoL, and disease activity in SLE, it is unclear how best to combine these data to make the most accurate predictions.

John Hanly, M.D., and fellow researchers at multiple international centers believe that, “A comprehensive instrument is required to more accurately predict the risk of adverse health outcomes among SLE patients.”

Frailty, a quantification of a patient’s susceptibility to adverse outcomes, has been used in the geriatric population successfully to predict outcomes. A frailty index, so to speak, may also be useful in predicting adverse outcomes and mortality in SLE.

The authors sought to construct a frailty index (FI) for SLE using established predictive measures with the aim of evaluating the ability a SLICC-FI to predict mortality within the SLICC inception cohort. The SLICC-FI was assessed further for it’s prognostic ability in comparison with existing SLE measures.

THE STUDY

The authors conducted a secondary analysis of the SLICC inception cohort. 1826 SLE patients were recruited from 1999 to 2011 from 31 international sites. Baseline assessments were made and then annually based on ACR classification criteria. SLICC/ACR-DI, SLE disease activity index (SLEDAI-2K), and HRQoL (Medical Outcomes Survey Short-Form 36 (SF-36)) were measured at each evaluation along with pertinent laboratory values.

The frailty index was constructed by establishing a baseline dataset consisting of the first visit for each patient at which both the SDI and the SF-36 were completed. Health deficit variables were determined covering multiple organ systems related to disease activity, comorbidities, and functional status. Each deficit was given a numeric score to be used in the frailty index. The SLICC-FI score is the sum of an individual’s health deficit scores divided by the total number of deficits.

Baseline SLICC-FI scores ranged from 0 to 0.51, with a median (I.Q.R.) of 0.16 (0.11–0.22) and a higher mean (S.D.) of 0.17 (0.08). After adjusting for age, male sex was associated with lower baseline SLICC-FI scores (β=-0.02; p=0.01).
At baseline, higher SLICC-FI values were associated with higher SDI (p<0.0001) and SLEDAI-2K (p<0.0001) scores. There was a moderately strong, negative association between SLICC-FI values and SF-36 Physical Component Summary (PCS) scores (p<0.0001). Higher SLICC-FI scores were also associated with lower SF-36 Mental Component Summary (MCS) scores (p<0.0001) at baseline.

There were 1,507 patients with final study visits after a mean follow-up of 7.2 years from baseline. Compared to baseline, these patients had less active disease and more organ damage at last follow-up, although 721 patients (47.8%) still had no organ damage at their last visit.

Similar to baseline, SLICC-FI values at last follow-up were positively associated with both SDI (p<0.0001) and SLEDAI-2K (p<0.0001) and also remained negatively associated with SF-36 PCS (p<0.0001) and MCS (p<0.0001 scores at last follow-up.

Higher baseline SLICC-FI values (per 0.05 increment) were associated with an increased risk of mortality and there was a persistent association between higher baseline SDI scores and increased mortality risk following multivariable adjustment.

FINAL THOUGHTS

Using a frailty index (FI) to predict adverse outcomes and mortality in SLE is feasible and effective. The SLICC-FI correlated well with existing measures of SLE disease activity, organ damage, and HRQoL.

Dr. Hanly and colleagues state, “In a well-characterized, international cohort of recently-diagnosed SLE patients, we have demonstrated the feasibility of using an FI to quantify vulnerability to adverse outcomes in SLE.”

Clinicians should expect the SLICC-FI to perform similarly to other frailty indices used in non-SLE patients and feel comfortable using it to predict future adverse outcomes.

Of note, seeing that the SLICC-FI scores can decrease, unlike the SDI scores, is in line with the notion that frailty itself can be reversed with proper treatment. Further, it is encouraging that many patients made it to follow-up with out any organ damage.

The authors should be commended on putting a new spin on an established measure, the frailty index, giving rheumatologists and other clinicians yet another tool to help individualize treatment and predict outcomes in SLE.

ABOUT THE AUTHOR

Gregory M. Weiss, M.D., is a cardiothoracic anesthesiologist practicing in Virginia. He is a frequent contributor to Rheumatology Network.

REFERENCE

Legge, A. , Kirkland, S. , Rockwood, K. , et al. Evaluating the properties of a frailty index and its association with mortality risk among patients with systemic lupus erythematosus. Arthritis Rheumatol. 16 February 2019, Accepted Author Manuscript. doi:10.1002/art.40859