Background Malnutrition is a frequently reported complication in patients with systemic sclerosis (SSc) . Especially low fat free mass (FFM) has been identified a prognostic factor for morbidity and mortality. Different methods are available to assess body composition. Bioelectrical impedance analysis (BIA) is a bedside method that has not yet been validated in this patient group.
Objectives To validate BIA against whole body dual-energy x-ray absorptiometry (DXA), for the assessment of body composition in patients with SSc.
Methods Body composition was assessed in 72 patients with whole body DXA (Hologic, Discovery A) and BIA (Bodystat Quadscan 400). The Geneva equation  was used to estimate FFM. The agreement between BIA and whole body DXA was assessed with Bland-Altman analysis and intraclass correlation coefficients (ICCs). The occurrence of malnutrition was assessed and defined as fat free mass index (FFMI) ≤14.5 kg/m2 for women or ≤16.6 kg/m2 for men .
Results No difference was found between BIA and whole body DXA for the assessment of FFM as predicted by the Geneva equation (mean difference 0.02 ± 2.4 kg). ICC was 0.97 (95% CI: 0.95–0.98). The 95% limits of agreement, as assessed by Bland-Altman analysis were -4.6 kg and 4.6 kg. Despite normal BMIs (24.6 ± 4.3 kg/m2), malnutrition was found in 14 (19.4%) patients with SSc.
Conclusions This study shows acceptable validity of BIA in determining FFM in patients with SSc on a group level, while on an individual level, FFM may vary by 4.6 kg. This study also demonstrated a high prevalence (19.4%) of malnutrition in patients with SSc, underlining the necessity of assessing body composition in this patient group.
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Disclosure of Interest None declared