Sarcopenic obesity in patients with rheumatoid arthritis: Diagnostic possibilities of ultrasound examination of fat and muscle tissue of the lower limb
Abstract
Introduction . Sarcopenic obesity (SO) is a pathological condition characterized by the combination of sarcopenia and a high percentage of body fat mass, as determined by instrumental assessment of body composition. The diagnosis of SO in patients with rheumatoid arthritis (RA) is difficult due to the low informativeness of muscle strength assessment tests and the limited availability of body composition analysis by DXA. Aim . To evaluate the possibilities of ultrasound examination of fat and muscle tissue of the lower limbs for the diagnosis of SO in women with RA. Materials and methods . 52 women with RA (mean age 56.9 ± 8.2 years) were included. A full-body DXA scan was performed. The diagnosis of SO was based on a combination of appendicular muscle mass index < 5.5 kg/m 2 and total fat ≥ 35%. Ultrasound was used to measure the thickness of subcutaneous fat (TSF-AT) and muscles of the anterior thigh (TM-AT), the index of TSF-AT/TM-AT, the pennation angle of the medial head of the gastrocnemius muscle (PA-MHGM) and the thickness of subcutaneous fat of the calf (TSF-C). Results. SO was diagnosed in 13 (25.0%) women. Significant rank correlations were found between SO and TSF-AT (τ = 0.24), TM-AT (τ = –0.33), and the index TSF-AT/TM-AT (τ = 0.34), whereas no associations were observed with the PA-MHGM and TSF-C. ROC-analysis showed that the index of TSF-AT/TM-AT had the best area under the curve (AUC) for the sensitivity-specificity ratio for diagnosis of SO (AUC = 0.777, p < 0.001). At a cut-off point of > 1.02, sensitivity and specificity were 53.9% and 84.6%, respectively. Conclusion. The value of TSF-AT/TM-AT > 1.02 can be considered as a potential diagnostic marker of SO in patients with RA. In combination with measuring the strength and physical performance of skeletal muscles, this approach provides an accessible, radiation-free diagnostic method for SO in routine clinical practice.