Abstract
Background/ObjectivesSeveral studies have addressed the validity of ultrasound (US) for body composition assessment, but few have evaluated its reliability. This study aimed to determine the reliability of percent body fat (%BF) estimates using A-mode US in a heterogeneous sample.Subjects/MethodsA group of 144 healthy adults (81 men and 63 women), 30.4 (10.1) years (mean (SD)), BMI 24.6 (4.7) kg/m2, completed 6 consecutive measurements of the subcutaneous fat layer thickness at 8 anatomical sites. The measurements were done, alternatively, by two testers, using a BodyMetrix™ instrument. To compute %BF, 4 formulas from the BodyView™ software were applied: 7-sites Jackson and Pollock, 3-sites Jackson and Pollock, 3-sites Pollock, and 1-point biceps.ResultsThe formula with the most anatomic sites provided the best reliability quantified by the following measures: intraclass correlation coefficient (ICC) = 0.979 for Tester 1 (T1) and 0.985 for T2, technical error of measurement (TEM) = 1.07% BF for T1 and 0.89% BF for T2, and minimal detectable change (MDC) = 2.95% BF for T1, and 2.47% BF for T2. The intertester bias was −0.5% BF, whereas the intertester ICC was 0.972. The intertester MDC was 3.43% BF for the entire sample, 3.24% BF for men, and 3.65% BF for women.ConclusionsA-mode US is highly reliable for %BF assessments, but it is more precise for men than for women. Examiner performance is a source of variability that needs to be mitigated to further improve the precision of this technique.
Highlights
The evaluation of human body composition is important in sports medicine [1] and in clinical disciplines in which the treatment plan includes body weight management
Measurements combined with anthropometry provided percent body fat (%BF = fat mass (FM)/(FM + fat-free mass (FFM)) × 100%) estimates in good agreement with dual energy x-ray absorptiometry (DXA), but with significant bias compared to air displacement plethysmography (ADP) and bioelectrical impedance analysis (BIA) [9]
minimal detectable change (MDC) was calculated as 1:96 Á 2 Á standard error of measurement (SEM), where 1.96 is the two-sidpeffidffi z-score that corresponds to the 95% confidence level and 2 accounts for the variance of two measurements [28, 29]
Summary
We hypothesized that the intertester bias originated from an underestimation of the subcutaneous adipose tissue layer thicknesses by T1 as compared to T2 To test this hypothesis, we computed S7—the sum of the 7 adipose layer thicknesses involved in the JP7 formula [31, 32]—and performed a paired t-test to decide whether the difference between the means of S7 recorded by the two testers is significantly different from zero. The average of S7 computed from all 3n measurements performed by T1 was 75.6 mm, whereas the corresponding quantity recorded by T2 was 78.0 mm; their difference, −2.4 mm, was significantly different from zero (P = 7.7 × 10−6), with a 95% CI [−3.3, −1.3] mm This underestimation was more pronounced for women (−3.0 mm; 95% CI [−4.7, −1.3] mm; P = 5.4 × 10−4) than for men (−1.8 mm; 95% CI [−3.0, −0.6] mm; P = 4.5 × 10−3), leading to a larger intertester bias for women (Fig. S5)
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