Predictive value of adductor pollicis muscle thickness for ultrasound-based sarcopenia in older adults

Background: The adductor pollicis muscle thickness (APMT) is least affected by subcutaneous adipose tissue and can be measured externally. The aim of this study is to identify the predictive value of APMT for the diagnosis of ultrasonography-based sarcopenia. Methods: A total of 245 outpatients who were aged >= 65 years (49 with sarcopenia and 196 without sarcopenia) were included in this cross-sectional study. Patients with knee or hip replacement, advanced dementia, cerebrovascular disease, neurodegenerative disease, or decompensated heart failure and those using drugs that affect muscle functions, such as steroids, were excluded. Comprehensive geriatric assessments and anthropometric measurements of the patients were performed. APMT was assessed with a skinfold caliper. The diagnosis of sarcopenia was based on a low Sonographic Thigh Adjustment Ratio (STAR) index (anterior thigh muscle thickness by ultrasonography/body mass index [BMI] ratio, cutoff points are <1.4 for men and <1.0 for women) and low handgrip strength. The predictive ability of APMT for ultrasound-based sarcopenia diagnosis was examined. Results: There was no significant difference in terms of arm and calf circumference and BMI between the sarcopenic and nonsarcopenic groups. APMT, handgrip strength, anterior thigh muscle thickness, and gait speed were significantly lower in the patients with sarcopenia. The best cutoff points of APMT for sarcopenia were <= 16.5 for women and <= 21.5 for men with areas under the curve of 0.70 and 0.66, respectively, and negative predictive values of 91.2 and 94.3, respectively (P < 0.001). Conclusion: APMT can be a useful anthropometric marker for ultrasound-based sarcopenia diagnosis.