Reference Values for Skeletal Muscle Mass at the Third Lumbar Vertebral Level Measured by Computed Tomography in a Healthy Korean Population

Background: Sarcopenia is defined as the loss of skeletal muscle mass and is associated with negative clinical outcomes. This study aimed to establish sex-specific cutoff values for the skeletal muscle area (SMA) and skeletal muscle index (SMI) at the third lumbar vertebral (L3) level using computed tomography (CT) imaging to identify sarcopenia in healthy Korean liver donors. Methods: This retrospective study included 659 healthy liver donors (408 men and 251 women) aged 20 to 60 years who had undergone abdominal CT examinations between January 2017 and December 2018. Assessment of body composition was performed with an automated segmentation technique using a deep-learning system. Sex-specific SMA and SMI distributions were assessed, and cutoff values for determining sarcopenia were defined as values at either two standard deviations (SDs) below the mean reference value or below the fifth percentile. Results: Using the SD definition, cutoff values for SMA and SMI were 117.04 cm(2) and 39.33 cm(2)/m(2) , respectively, in men and 71.39 cm(2) and 27.77 cm(2)/m(2), respectively, in women. Using the fifth percentile definition, cutoff values for SMA and SMI were 126.88 cm(2) and 40.96 cm(2)/m(2) , respectively, in men and 78.85 cm(2) and 30.60 cm(2)/m(2), respectively, in women. Conclusion: Our data provide sex-specific cutoff values for the SMA and SMI at the L3 level measured by CT imaging in a healthy Korean population, which may be applicable for identifying sarcopenia in this population.