Screening for sarcopenia and obesity by measuring thigh muscle and fat thickness by ultrasound in patients with rheumatoid arthritis

OBJECTIVES: Sarcopenia is relatively common in rheumatoid arthritis (RA) patients. Thicknesses of the quadriceps muscle and fat are easily measured by ultrasound (US) and are known to be related to skeletal muscle mass and fat mass, respectively. METHODS: Eighty-four patients enrolled in the prospective correlation research of sarcopenia, skeletal muscle, and disease activity in rheumatoid arthritis study (UMIN000023744) underwent US examinations of anterior thigh muscle thickness (MT) and fat thickness (FT). Muscle and body fat (BF) mass were also examined by a body composition analyzer. Whether MT and FT were related to sarcopenia and obesity was examined. RESULTS: MT was significantly lower in RA patients with sarcopenia than in those without (23.8 vs 28.2 mm, P = 0.001). MT was related to sarcopenia (men: r = 0.56, P = 0.02, women: r = 0.32, P = 0.01). The cut-off value of MT for sarcopenia was 24.7 mm in men and 19.7 mm in women on receiver operating characteristic curve analyses. FT was correlated with BF percentage (%BF; men: r = 0.66, P < 0.01, women: r = 0.62, P < 0.001), which was estimated by 2.04xFT+8.53 in men and 1.2xFT+17.42 in women by a simple linear regression model. This means that FT ≥ 8.1 mm in men and FT ≥ 14.6 mm in women indicated obesity. CONCLUSIONS: US examination of the anterior thigh was useful to detect sarcopenia and obesity in RA patients.