Equation missed most low-muscle-mass cases in Chinese adults

In a retrospective observational study, researchers assessed 501 Chinese adults who underwent whole-body scans during routine health examinations between 2016 and 2022. They tested a published equation based on body measurements against dual-energy X-ray absorptiometry, a scan that measures body composition. The equation estimated muscle mass in the arms and legs, which researchers adjusted for height to create a muscle-mass index.

The muscle-mass estimates closely tracked scan measurements but overestimated them by an average of 1.25 kg. Agreement weakened for the height-adjusted index. Applying scan-based thresholds to that index missed 97 of 123 scan-defined low-muscle-mass cases. Adjusting the equation locally reduced prediction error but left disagreement for individuals. The authors advised against using either version alone when classification relies on fixed muscle-mass thresholds.