Reliability and Validity of A-Mode Ultrasound to Quantify Body Composition

Immobilization and inadequate nutrition after high-energy trauma result in loss of lean muscle mass. Body composition [percent body fat (%BF), fat mass (FM), fat-free mass (FFM)] is traditionally quantified with techniques that require expensive equipment and/or ionizing radiation. The purpose of this study was to assess reliability and validity of amplitude-mode (A-mode) ultrasound (US) to quantify body composition for use in a randomized clinical trial assessing interventions to prevent muscle loss in young individuals after high-energy musculoskeletal trauma.

Thirty-one volunteer subjects underwent body composition assessments using A-mode US and air displacement plethysmography (ADP). Independent raters performed 2 serial US measures. The same raters performed body composition assessment in 12 consecutive subjects that sustained acute musculoskeletal trauma indicated for surgery. Test-retest and inter-rater reliability were assessed using intraclass correlation coefficient (ICC). Agreement between US and ADP was assessed with Bland-Altman analysis.

Test-retest and inter-rater reliability was excellent for volunteer subjects, with ICC values (%BF, FM, and FFM) of 0.87, 0.90, and 0.99 (rater 1); 0.80, 0.82, and 0.98 (rater 2). FFM measured by US was strongly correlated with ADP measures (r = 0.9635, P < 0.05). Bland-Altman analysis demonstrated no systematic bias between US and ADP measures of body composition. In trauma subjects, the inter-rater reliability was excellent, with ICCs of 0.96, 0.98, and 0.99 for %BF, FM, and FFM, respectively.

A-mode US is a relatively low-cost tool that provides reliable estimates of body composition and is a viable alternative for monitoring body composition in young, healthy patients.