A Comparison of Muscle Function, Mass, and Quality in Liver Transplant Candidates: Results From the Functional Assessment in Liver Transplantation Study

Background. Sarcopenia and functional impairment are common and lethal extrahepatic manifestations of cirrhosis. We aimed to determine the association between computed tomography (CT)-based measures of muscle mass and quality (sarcopenia) and performance-based measures of muscle function. Methods. Adults listed for liver transplant underwent testing of muscle function (grip strength, Short Physical Performance Battery [SPPB]) within 3 months of abdominal CT. Muscle mass (cm(2)/m(2)) = total cross-sectional area of psoas, paraspinal, and abdominal wall muscles at L3 on CT, normalized for height. Muscle quality = mean Hounsfield units for total skeletal muscle area at L3. Results. Among 292 candidates, median grip strength was 31 kg, SPPB score was 11, muscle mass was 49 cm2/m2, and muscle quality was 35 Hounsfield units. Grip strength weakly correlated with musclemass (rho = 0.26, P < 0.001) and quality (rho = 0.27, P < 0.001) inmen, and muscle quality (rho = 0.23, P = 0.02), but not muscle mass, in women. Short Physical Performance Battery correlated weakly with muscle quality in men (rho = 0.38, P < 0.001) and women (rho = 0.25, P = 0.02), however, did not correlate with muscle mass in men or women. After adjustment for sex, model for end-stage liver disease (MELD)-Na, hepatocellular carcinoma, and body mass index, grip strength (hazard ratio [HR], 0.74; 95% confidence interval [95% CI], 0.59-0.92; P = 0.008), SPPB (HR, 0.89; 95% CI, 0.82-0.97; P = 0.01), and muscle quality (HR, 0.77; 95% CI, 0.63-0.95; P = 0.02) were associated with wait list mortality, but muscle mass was not (HR, 0.91; 95% CI, 0.75-1.11; P = 0.35). Conclusions. Performance-based tests of muscle function are only modestly associated with CT-based muscle measures. Given that they predict waitlist mortality and can be conducted quickly and economically, tests of muscle function may have greater clinical utility than CT-based measures of sarcopenia.