The accuracy of body mass index and calf circumference values when assessing sarcopenia in a multi-ethnic cohort of middle-aged and older adults: West China health and aging trend study results.

Objective: This analysis was designed to explore the utility of body mass index (BMI) and calf circumference (CC) values in the diagnosis of sarcopenia. Methods: A cross-sectional analysis of community-dwelling adults ≥50 years old was conducted. An InBody 770 bioimpedance analysis (BIA) device was used for measuring muscle mass, a grip-strength dynamometer was used to assess muscle strength, and a 4 m gait speed (GS) analysis was used to gauge physical function. The Asian Working Group for Sarcopenia (AWGS) 2019 criteria were used to define sarcopenia. The cut-off values for BMI and CC were based on the computed Younden's index values and AWGS 2019 criteria, respectively. The area under the ROC curves (AUC), specificity, sensitivity, and positive and negative predictive values (PPV and NPV) were calculated to establish the value of BMI and CC for the diagnosis of sarcopenia. Results: In total, the data of 4177 participants ≥50 years of age were analyzed. These included 2668 (63.9%) females and 1509 (36.1%) males. Of these participants, 946 (22.6%) met the criteria for sarcopenia, including 408 (27%) males and 538 (20.2%) females. The sensitivity, specificity, and NPVs obtained when using BMI and CC values to predict sarcopenia were as follows: 84.03%/65.51%/0.90 and 74.76%/83.51%/0.87, respectively, in males; 87.36%/64.12%/0.94 and 78.25%/82.09%/0.93, in females. The respective AUC values for BMI and CC in males were 0.83 (0.80-0.85) and 0.85 (0.83-0.88), while in females they were 0.85 (0.83-0.87) and 0.88 (0.87-0.90). Conclusions: These data suggest that BMI and CC can both serve as accurate predictors of sarcopenic incidence in a multi-ethnic population ≥50 years of age. The specificity values for BMI were relatively low in both males and females, however, underscoring the relative advantages of measuring CC when assessing individual sarcopenia risk.