Validity of Bioelectrical Impedance Analysis for the Assessment of Body Composition in Patients With Systemic Sclerosis.

BIA demonstrated excellent agreement with DXA (CCC > 0.900) for multiple body composition measures in patients with systemic sclerosis.

• Excellent agreement (CCC > 0.900) was found for ASM/BMI (Δ = 0.032; 95% CI 0.019–0.045), FM (Δ = −0.401; 95% CI −0.804 to 0.003), FMI (Δ = −0.190; 95% CI −0.366 to −0.015), and FFM (Δ = −0.010; 95% CI −0.415 to 0.395).
• Good concordance (CCC 0.750–0.900) was observed for ASM (Δ = 0.803; 95% CI 0.518–1.088).
• Agreement was evaluated using Bland-Altman analysis and Lin's concordance correlation coefficient (CCC).
• The study included 100 patients with SSc (91% women; mean age 60.1 ± 11.5 years; median disease duration 11.5 [5.0–20.3] years).

BIA demonstrated high diagnostic accuracy for detecting myopenia in women with systemic sclerosis based on ROC curve analysis.

• AUC for ASM was 0.956 (95% CI 0.908–1.000) in women.
• AUC for ASMI was 0.878 (95% CI 0.763–0.993) in women.
• AUC for ASM/BMI was 0.969 (95% CI 0.935–1.000) in women.
• The optimal ASM/BMI cut-off of 0.506 yielded 100% sensitivity and 90.1% specificity (PPV 55.6%, NPV 100%).

The study population consisted of 100 SSc patients with a predominance of limited cutaneous subtype and long disease duration.

• 91% of participants were women, with a mean age of 60.1 ± 11.5 years.
• Median disease duration was 11.5 [5.0–20.3] years.
• Disease subtypes comprised 23% diffuse cutaneous, 61% limited cutaneous, and 16% sine scleroderma.
• This was a cross-sectional study design.

The BIA device used (InBody 370s) was compared against DXA (Lunar Prodigy Primo) as the reference standard for multiple body composition parameters.

• Parameters assessed included FM, FMI, FFM, FFMI, ASM, ASMI, and ASM adjusted by BMI (ASM/BMI).
• Myopenia was defined according to established muscle mass criteria.
• DXA is recommended by international guidelines as the reference standard for muscle mass evaluation in sarcopenia.
• Variability across BIA devices and assessment protocols may influence measurement accuracy, underscoring the need for validation in specific clinical populations.

Reduced muscle mass is common in systemic sclerosis and contributes to myopenia, sarcopenia and adverse clinical outcomes.

• SSc is characterized by vasculopathy and progressive fibrosis.
• BIA is noted as affordable, easy to use, and non-invasive, but its accessibility advantage over DXA motivates validation studies in specific clinical populations.
• The study authors highlight that DXA accessibility in routine clinical practice is limited, supporting the rationale for validating BIA in SSc.