The phase angle before transplantation can predict the status of low muscle mass after kidney transplantation.

Background: This study aimed to evaluate the association between phase angle, muscle strength, and muscle mass in patients undergoing kidney transplantation.

Methods: Patients whose pre- and follow-up phase angles were measured after kidney transplantation were enrolled. Phase angle and body composition were measured using a multi-frequency bioimpedance analysis device before and at 7 and 14 days and 3, 6, and 12 months after transplantation. Muscle strength was evaluated using handgrip strength (HGS). Low HGS was defined as < 28 kg in males and < 18 kg in females. Low muscle mass was defined as an appendicular lean mass index of < 7.0 kg/m² in males and < 5.7 kg/m² in females.

Results: Eighty-eight patients (mean age 52.3 ± 10.1 years) were analyzed. The mean phase angle of pre-transplantation was 5.0 ± 1.0°. Body fat percentage was significantly higher at 6 and 12 months after transplantation than pre-transplantation (P < 0.0001). Twelve months after kidney transplantation, the prevalence of low HGS decreased (pre-transplantation vs. 12 months post-transplantation: 28.4% vs. 17.0%), and the prevalence of low muscle mass (pre-transplantation vs. 12 months post-transplantation: 21.6% vs. 28.4%) increased. The pre-transplantation phase angle was significantly associated with low muscle mass at 12 months after kidney transplantation (odds ratio [OR]: 0.34; 95% confidence interval [CI]: 0.16-0.72; P = 0.005). The pre-transplantation phase angle was not significantly associated with low HGS (OR: 0.37; 95% CI 0.12-1.17; P = 0.090) 12 months after kidney transplantation.

Conclusions: Pre-transplantation phase angle can predict muscle mass status 12 months after kidney transplantation.