Agreement between bioimpedance-measured and calf-derived appendicular skeletal muscle mass in amyotrophic late

Over time, amyotrophic lateral sclerosis (ALS) has been considered an accelerated model of sarcopenia. However, muscle mass is rarely assessed in ALS patients. The aim of this study was to explore the agreement between bioelectrical impedance analysis (BIA)-measured and calf circumference (CC)-derived appendicular skeletal muscle mass index (ASMMI) in ALS patients. Body composition was assessed using anthropometric measures and BIA. Pearson analyses were used to assess correlations and Kappa (κ) statistics were used to evaluate agreement between BIA-measured and CC-derived ASMMI. CC predictive ability was assessed through the area under the receiver operating characteristic curve. A total of 61 ALS patients were included. The CC-ASMM was highly correlated with the BIA-ASMM (r = 0.830, p < 0.001) and CC-ASMMI was moderately correlated with BIA-ASMMI (r = 0.62, p < 0.001). Low CC-derived and BIA-derived ASMMI presented a moderate degree of agreement in the overall sample (k = 0.546, 95% CI 0.325–0.767) and in men (k = 0.432, 95% CI 0.056–0.809), while a substantial agreement was observed in women (k = 0.613, 95% CI 0.344–0.883). The optimal cut-off values for CC in identifying low ASMMI from the ROC analysis, were 34 cm for both sexes with an area under the curve (AUC) of 0.818 for men (sensitivity 80%, specificity 78.3%) and of 0.841 (sensitivity 83.3%, specificity 72.7%) for women.