Calf circumference cutoffs for detecting low muscle mass in older patients with subacute stroke: diagnostic accuracy and association with nutritional status

Disease-specific cutoffs are essential for accurately assessing low muscle mass. We aimed to determine calf circumference cutoffs for identifying low muscle mass in older patients with subacute stroke and to compare their diagnostic accuracy with those used across various disease-specific criteria. This single-center, cross-sectional study included older patients with subacute stroke using consecutive sampling. Low muscle mass was defined as an appendicular skeletal muscle mass index of less than 7.0 kg/m² in men and less than 5.7 kg/m² in women. Calf circumference was measured on the nonparetic side, and the maximum value was used. We assessed the diagnostic accuracy of the derived cutoffs using sensitivity, specificity, predictive values, likelihood ratios, and Matthews correlation coefficient (MCC). The study adhered to the Standards for Reporting Diagnostic Accuracy 2015 guidelines. Among 253 participants, 188 met the inclusion criteria. The optimal cutoffs were 31 cm for men and 30 cm for women. These cutoffs yielded a sensitivity of 0.78 [95% confidence interval (CI): 0.69-0.85], specificity of 0.71 (95% CI: 0.59-0.82), positive likelihood ratio of 2.73 (95% CI: 1.86-4.00), and MCC of 0.47 (95% CI: 0.36-0.62). Compared with criteria used across-disease groups, the newly derived cutoffs yielded higher specificity, a greater positive likelihood ratio, and an improved MCC. These cutoffs provide acceptable diagnostic accuracy for identifying low muscle mass in this patient population and may offer a practical screening option in clinical settings.