Imaging without biology: limitations of CT-derived psoas muscle volume as a standalone diagnostic criterion for sarcopenia

We comment on the study by Choi et al., which proposes CT-derived psoas muscle volume (PV) as a diagnostic indicator for sarcopenia. The study is well designed, using automated deep-learning-based CT segmentation for psoas muscle volume measurement, and adds to the growing interest in opportunistic CT-based muscle assessment. However, a few points may warrant consideration before wider clinical application. These include differences from current consensus definitions of sarcopenia, limitations related to the use of BIA as a reference standard, and the lack of validation against clinical outcomes. Furthermore, volumetric measures alone may not fully capture the histopathological changes associated with sarcopenia, including muscle fibre atrophy, fat infiltration, and neuromuscular denervation. We also note that applying T-score thresholds from osteoporosis to muscle volume is not straightforward, as no comparable outcome data currently exist to anchor these cut-offs in sarcopenia.