Development of a novel frailty index to predict mortality in patients with end-stage liver disease

Abstract

Cirrhosis is characterized by muscle wasting, malnutrition, and functional decline that confer excess mortality not well quantified by the Model for End-Stage Liver Disease (MELD) Sodium (MELDNa) score. We aimed to develop a frailty index to capture these extrahepatic complications of cirrhosis and enhance mortality prediction in patients with cirrhosis. Consecutive outpatients listed for liver transplantation at a single transplant center without MELD exceptions were assessed with candidate frailty measures. Best subset selection analyses with Cox regression identified subsets of frailty measures that predicted waitlist mortality (=death or delisting because of sickness). We selected the frailty index by balancing statistical accuracy with clinical utility. The net reclassification index (NRI) evaluated the %patients correctly reclassified by adding the frailty index to MELDNa. Included were 536 patients with cirrhosis with median MELDNa of 18. One hundred seven (20%) died/were delisted. The final frailty index consisted of: grip strength, chair stands, and balance. The ability of MELDNa and the frailty index to correctly rank patients according to their 3-month waitlist mortality risk (i.e., concordance-statistic) was 0.80 and 0.76, respectively, but 0.82 for MELDNa+frailty index together. Compared with MELDNa alone, MELDNa+frailty index correctly reclassified 16% of deaths/delistings (P = 0.005) and 3% of nondeaths/delistings (P = 0.17) with a total NRI of 19% (P < 0.001). Compared to those with robust frailty index scores (<20th percentile), cirrhotics with poor frailty index scores (>80th percentile) were more impaired by gait speed, difficulty with Instrumental Activities of Daily Living, exhaustion, and low physical activity (P < 0.001 for each).

Conclusion: Our frailty index for patients with cirrhosis, comprised of three performance-based metrics, has construct validity for the concept of frailty and improves risk prediction of waitlist mortality over MELDNa alone. (Hepatology 2017;66:564-574).

Figure 1

Distribution of frailty index scores for 536 outpatient cirrhotics awaiting liver transplantation. Higher values indicate a higher degree of frailty.

Figure 2

Predicted probabilities of survival for four patients with cirrhosis on the liver transplant waitlist, classified by a combination of MELDNa and frailty index scores. MELDNa scores (14 and 23) and frailty index scores (3.2=robust and 4.5=frail) were selected because they represented the bottom 20%ile and top 80%ile values for the cohort.