AB1820-HPR BIOELECTRICAL IMPEDANCE ANALYSIS SHOWED HIGH AGREEMENT AND SPECIFICITY TO ASSESSMENT OF LOW APPENDICULAR SKELETAL MUSCLE MASS IN WOMEN WITH SYSTEMIC SCLEROSIS: PRELIMINARY DATA

Abstract

BackgroundPatients with systemic sclerosis (SSc) are particularly prone to skeletal muscle wasting, affecting nearly one-third of patients, increasing the risk of disability[1,2]. To assess muscle mass, there are direct methods, such as magnetic resonance imaging, computed tomography and dual-energy X-ray absorptiometry (DXA), considered the gold standard[3]. DXA is widely used in clinical practice and in population studies, but it has some disadvantages, such as specific technical skills and higher costs[3]. Bioelectrical impedance analysis (BIA) is a validated method in healthy individuals of body composition assessment with greater affordability and minimum requirements[4]. To our knowledge, in patients with SSc only one study compared DXA with BIA. Soanjer et al found agreement between these two techniques only for fat-free mass, without evaluating appendicular skeletal muscle mass (ASM)[5].Objectives(1) Our objective was to compare ASM measured by BIA versus DXA and (2) to verify the associations with clinical features in women with SSc.MethodsWomen with SSc according to ACR/EULAR 2013 criteria were consecutively included at a tertiary public hospital in Rio Grande do Sul, Brazil (Hospital de Clínicas de Porto Alegre, HCPA) in 2022. Modified Rodnan’s skin score (mRSS), EUSTAR activity index were calculated. The ASM by BIA (In Body 370s) and DXA (GE FamBeam 4500A) were calculated from sum lean mass of arm and legs (kg). Low muscle mass (BIA or DXA) was defined according to the European Working Group on Sarcopenia in Older People 2 (EWGSOP2) less than 15 kg. Pearson’s and intraclass correlation coefficients, dependent samples t-test and simple linear regression for Bland–Altman plot were performed. The significance level was set at p<0.05.ResultsUntil this moment, 62 women with SSc were included. The mean age was 62.0 ± 10.1 years-old and median disease duration was 15.0 (7.0–21.0) years. Forty-one patients (66.1%) had limited cutaneous disease, 14 (22.6%) diffuse-cutaneous and 7 (11.3%)sine scleroderma. The median mRSS was 4.0 (2.0–8.0) and the EUSTAR index was 1.5 (0.6 - 2.4). The mean appendicular skeletal muscle mass measured by DXA was 16.0 ± 2.2 kg while by BIA was 15.5 ± 2.3 kg (Δ = 0.5 kg; p = 0.005), underestimating the ASM. On other hand, the mean differences between DXA and BIA showed within the confidence interval (p= 0.358; CI 95%: -2.8 – 1.8; Figure 1). ASM by BIA was strongly correlated (r= 0.866, p < 0.001) and had a high agreement (Intraclass Correlation Coefficient = 0.919, p < 0.001) with ASM by DXA. We found only weak association between ASM by BIA and age (r= -0.282; p= 0.026). Low muscle mass in women with SSc was found in 18 patients (29%) by DXA and in 26 patients (42%) by BIA with a sensitivity of 80% and specificity of 94%.ConclusionBIA and DXA show high correlation and agreement in ASM assessment of women with SSc. Our findings suggest BIA as a useful tool due to its high specificity with DXA for the early assessment of low ASM in women with SSc. Furthermore, completion of this study is needed to confirm these results.