Computed Tomography–Derived Thoracic Muscle Size as an Indicator of Sarcopenia in People With Advanced Lung Disease

Abstract

Purpose: Computed tomography (CT) of the chest is routinely performed in people with lung disease; however, the utility of measuring thoracic muscle size to assess the presence of sarcopenia (low muscle mass and function) has not been studied. The purpose of this study was to examine the reliability and validity of thoracic muscle size obtained from chest CT as a surrogate of sarcopenia. Methods: In this observational study, chest CT was obtained from routine clinical evaluation in 32 individuals with advanced lung disease awaiting lung transplantation. Thoracic muscle area from vertebral levels T4–T6 was manually segmented using Slice-O-Matic software, and average muscle cross-sectional area (CSA) and muscle volume were calculated. Measures of sarcopenia included quadriceps CSA and thickness from ultrasound, quadriceps, and biceps torque and short physical performance battery (SPPB). Results: Intrareliability and interrater reliability for muscle CSA were high (intraclass correlation coefficient = 0.96, 0.99; absolute difference = 0.61, 1.7 cm2, respectively). Thoracic muscle CSAs and volume correlated with quadriceps size and limb muscle strength (r = 0.56–0.71, P < .001) but not SPPB. Cross-sectional areas from single slices at T4–T6 were highly correlated with muscle volume (r = 0.89–0.91, P < .001). Conclusions: Thoracic muscle size seems to be a reliable and valid technique that can be applied in large studies evaluating the presence of sarcopenia in patients with advanced lung disease.