Standardizing calf circumference measurements to improve muscle mass assessment

Calf circumference (CC) is a simple anthropometric marker of muscle mass cited in several clinical guidelines. However, whether measurement position influences results has not been studied. We evaluated agreement among CC measurements across different positions.

This cross-sectional study was conducted among hospitalized patients (≥18 years). CC was measured at the largest circumference of the right calf in orthostatic (CC_ort), sitting (CC_sit), and supine (CC_sup) positions. Repeated-measures analysis of variance (RM-ANOVA) and the Tukey honestly significant difference post hoc tests were applied. Agreement between measurements was evaluated using Lin's concordance correlation coefficient and Bland-Altman analysis. The technical error of measurement (TEM) and minimal detectable change (MDC) for the measurements were calculated.

Among 193 patients (mean age: 57.7 ± 15.0 years, 52.8% females), CC_sit was highest, significantly exceeding CC_ort and CC_sup. TEM ranged from 0.47 to 0.60 cm across positions, corresponding to a relative error of approximately 1.5%. MDC ranged from 1.30 to 1.67 cm, which was higher than the mean differences among the positions. Cohen's kappa indicated good agreement among the CC_sit, CC_ort, and CC_sup classifications. A small proportional bias was identified between CC_ort and CC_sit. The width of the limits of agreement was 1.60 cm between CC_sit and CC_ort, and 2.29 cm between CC_sit and CC_sup.

CC values differed slightly across body positions, within the expected measurement error, and showed acceptable agreement. However, the wide limits of agreement preclude interchangeability at the individual level, suggesting that consistent positions should be used in longitudinal studies.