Abdominal CT measurements of body composition and waitlist mortality in kidney transplant candidates

Body mass index (BMI) is often used to determine kidney transplant (KT) candidacy. However, this measure of body composition has several limitations, including the inability to accurately capture dry weight. Objective computed tomography (CT)-based measures may improve pre- KT risk stratification and capture physiologic aging more accurately. We quantified the association between CT-based body composition measurements and waitlist mortality in a retrospective study of 828 KT candidates (2010-2022) with clinically obtained CT scans using adjusted competing risk regression. 42.5% of candidates had myopenia, 11.4% had myopenic obesity, 68.8% had myosteatosis, 24.8% had sarcopenia (probable=11.2%, confirmed=10.5%, and severe=3.1%) and 8.6% had sarcopenic obesity. Myopenia, myopenic obesity and sarcopenic obesity were not associated with mortality. Patients with myosteatosis (aSHR=1.62, 95%CI:1.07-2.45) or sarcopenia (probable: aSHR=1.78, 95%CI:1.10-2.88; confirmed: aSHR=1.68, 95%CI:1.01-2.82 and severe: aSHR=2.51, 95%CI:1.12-5.66) were at increased risks of mortality. When stratified by age, myopenic obesity (aSHR=2.21, 95%CI:1.28-3.83; p-interaction=0.005) and myosteatosis (aSHR=1.95, 95%CI:1.18-3.21; p-interaction=0.038) were associated with elevated risk only among candidates<65 years. Myopenic obesity was only associated with waitlist mortality among frail candidates (aHR=2.54, 95%CI:1.28-5.05; p-interaction=0.021). Transplant centers should consider using body composition metrics in addition to BMI, when a CT scan is available, to improve pre-KT risk stratification at KT evaluation.