Phase angle as a reproducible bedside tool to assess reduced muscle mass in patients with decompensated cirrhosis and ascites: An observational cross-sectional study

Abstract

Background: Reduced muscle mass in patients with cirrhosis is linked to poor clinical outcomes. Bioimpedance analysis estimates fat mass (FM), fat-free mass (FFM), and phase angle (PhA), a marker of cell membrane integrity correlating with computed tomography–based muscle mass assessments. We hypothesized that PhA would remain stable after paracentesis. Methods: Bioelectrical impedance was measured in patients with cirrhosis immediately before and after paracentesis using a 256-frequency bioimpedance spectroscopy device. We assessed median paired differences (with 95% confidence intervals) for FM, FFM, and PhA. Reduced muscle mass was diagnosed using PhA thresholds of 5.4 for women and 5.6 for men, based on previous cross-sectional validation against skeletal muscle index. Results: The study included 32 participants with median age of 60 (IQR: 55–67), 60% male, median model for end stage liver disease Na (MELD-Na) score of 18 (IQR: 14–21), and median paracentesis volume of 6 liters (loss of 5.7 kg). At baseline, 97% had reduced muscle mass based on PhA thresholds. Significant differences were observed between pre-paracentesis and post-paracentesis measurements for FM and FFM (P < 0.05). PhA remained stable (P = 0.208), with a slight nonsignificant increase of 0.1° from pre-paracentesis to post-paracentesis. Sensitivity analysis showed change in reduced muscle mass diagnosis for only one participant. Conclusions: FM and FFM levels before and after paracentesis were significantly different, suggesting that these tests would not be accurate in patients with large fluid shifts. PhA measurements were not significantly affected by ascitic fluid shifts after paracentesis, suggesting that PhA may reliably monitor muscle mass in patients, regardless of ascites.