Sarcopenia may be associated with the long-term prognosis of renal transplant recipients, so it is essential to early and rapidly screening for sarcopenia in these patients. Studies suggest that calf circumference may be an effective indicator in early screening for sarcopenia.

To investigate the relationship between calf circumference and sarcopenia, and to explore the feasibility of using calf circumference as a predictive marker for sarcopenia in kidney transplant recipients.

We selected 80 kidney transplant recipients who were treated in the department of organ transplantation of Guangdong Second Provincial General Hospital from October 2021 to June 2022 as the subjects. Demographic information (sex, age, educational attainment, marital status) , anthropometric indicators〔height, weight, body mass index (BMI) , calf circumference, mid-arm circumference (MAC) , triceps skin-fold thickness (TSF) , arm muscle circumference (AMC) , waist circumference, hip circumference, waist-to-hip ratio〕, muscle strength indicators (grip strength, pinch strength) , body composition indicators〔appendicular skeletal muscle mass (ASM) , skeletal muscle mass index (SMI) , 50 kHz phase angle (PhA) , body cell mass (BCM) , intracellular and extracellular fluids〕 were collected. Sarcopenia was diagnosed by the Asian Working Group for Sarcopenia 2019 consensus. Kidney transplant recipients who meet the diagnostic criteria were included in the sarcopenia group, and those who do not meet the diagnostic criteria were included in the non-sarcopenia group. Demographic information, anthropometric indicators, muscle strength indicators, and body composition indicators between sarcopenia and non-sarcopenia patient groups were compared by sex. Pearson correlation analysis and Spearman rank correlation analysis were used to observe the correlation of calf circumference with diagnostic indicators of sarcopenia (ASM, SMI, grip strength) . Univariate and multivariate logistic regression analyses were used to explore the influencing factors of sarcopenia. The predictive value of calf circumference for sarcopenia in kidney transplant of male and female subjects was analyzed by using the receiver operating characteristic (ROC) curve, and the area under the curve (AUC) , sensitivity, specificity and optimal cut-off values were calculated.

A total of 80 patients〔51 men (63.8%) and 29 women (36.2%) 〕 with an average age of (44.3±11.7) years were included, including 19 (23.75%) with sarcopenia, and 61 (76.25%) without. Sex-based analysis found that male patients with sarcopenia group had lower values of weight, BMI, calf circumference, MAC, TSF, hip circumference, grip strength, pinch strength, ASM, SMI, PhA, BCM, extracellular fluid and intracellular fluid than those without (P<0.05) . Female patients with sarcopenia had lower values of weight, BMI, calf circumference, waist circumference, hip circumference, waist-to-hip ratio, ASM, SMI, BCM, extracellular fluid and intracellular fluid than those without (P<0.05) . Correlation analysis showed that the calf circumference had a positive correlation with ASM, SMI and grip strength in both male kidney transplants (r_s=0.545, P<0.001; r_s=0.540, P<0.001; r_s=0.340, P=0.015) and female kidney transplants (r_s=0.499, P=0.006; r_s=0.578, P=0.001; r=0.426, P=0.021) . Multivariate Logistic regression analysis showed that calf circumference was associated with sarcopenia in kidney transplant〔OR=0.699, 95%CI (0.051, 0.975) , P=0.035〕. ROC analysis revealed that the AUC of calf circumference predicting sarcopenia in kidney transplant of male subjects was 0.799, with the optimal cut-off value, sensitivity and specificity of 33.3 cm, 83.3% and 74.4%, respectively. And the AUC of calf circumference predicting sarcopenia in kidney transplant of female patients was 0.851, with the optimal cut-off value, sensitivity and specificity of 32.2 cm, 100.0% and 59.1%, respectively.

Calf circumference is associated with sarcopenia and can be used as a predictive marker for early screening of sarcopenia in kidney transplant recipients. However, its predictive value needs to be verified further by large-sample cohort studies, and thus to better promote early clinical screening of sarcopenia in kidney transplant recipients to effectively improve their quality of life and prognosis.