The relationship between the psoas muscle index (PMI) and the appendicular skeletal muscle index (ASMI) in patients with compensated advanced chronic liver disease (cACLD) is not yet understood. Our goal is to determine which level of the lumbar spine best represents the appendicular skeletal muscle.

This retrospective study involved patients with cACLD between January 2020 and December 2021. We documented the patients' body weight, height, gait speed, handgrip strength, appendicular skeletal muscle measured by DXA, and psoas muscle area segmented on computed tomography or magnetic resonance imaging. Low muscle mass, as defined by the Asian working group for sarcopenia, is less than 7.0 kg/m² in males and less than 5.4 kg/m² in females. We analyzed the correlation between PMI and ASMI.

A total of 134 patients were enrolled in the study, with 74 being male and 60 being female. The mean age was 63.9 ± 7.7 years old. Significant associations (p < 0.001) were found between PMI of all levels and ASMI. In the analysis of Pearson's correlation coefficients, it was noted that the r value increased gradually in both males (r = 0.3197 at L2, 0.4006 at L3, 0.5769 at L4) and females (r = 0.3771 at L2, 0.4557 at L3, 0.5251 at L4). Similarly, the area under the curve (AUC) values predicting low muscle mass were as follows: for males, AUC=0.582 at L2, 0.619 at L3, 0.728 at L4; for females, AUC=0.685 at L2, 0.733 at L3, 0.744 at L4. The cut-off point for PMI in males was 4.12 at L2, 6.25 at L3, and 8.48 at L4, while in females was 2.61 at L2, 4.47 at L3, 6.07 at L4.

The Psoas muscle index can be used to assess the muscle mass status in patients with cACLD. Among the various levels that can be used, we recommend using the fourth inferior endplate of the lumbar spine, as it shows the highest correlation. Additionally, we suggest using a PMI cut-off point of 8.48 cm²/m² for males and 6.07 cm²/m² for females as a predictor of low muscle mass in Asian.