Assessing subcutaneous adipose tissue by simple and portable field instruments: Skinfolds versus A-mode ultrasound measurements

Abstract

PurposeThis study compared subcutaneous adipose tissue (SAT) measurements using a skinfold caliper and Renco Lean-Meater Series 12 A-mode portable ultrasound scanner (A-US). It aimed to assess their inter- and intra-rater reliability and measure the agreement between both methods.MethodsEighty-four volunteers of different fitness levels were divided into three groups by Ʃ6 skinfolds: G1 ≤ 55 mm (n = 33 males); G2 > 55 mm (n = 32 males); G3 = 98.0 ± 52.3 mm (n = 19 females). Triceps, subscapular, biceps, iliac crest, supraspinal, abdominal, front thigh and medial calf were assessed by ultrasound and skinfolds. Two technicians for both tools performed triplicate measures. Intraclass correlation (ICC), technical error of measurement (TEM) and coefficients of variation (CVs) were applied for test-retest and inter-rater reliability. Non-Parametric statistics were used in order to establish possible statistical differences and correlation between skinfolds thickness and uncompressed subcutaneous adipose tissue thickness from ultrasound. The amount of agreement between both methods was assessed with Lin’s coefficient and a scatterplot of all site locations. A Bland-Altman plot was constructed to establish limits of agreement between groups and regression analysis was employed to assess the ability of skinfolds to explain the variance of ultrasound.ResultsTest-retest ICC for skinfolds and ultrasound were higher than 0.989 and 0.793, respectively. Inter-rater ICC for skinfolds was 0.999 with a 95% CI of 0.995 to 0.999 and for ultrasound was 0.755 with a much larger 95% CI of 0.622 to 0.841. TEMs (> 8.50%) and CVs (> 6.72%) compromised ultrasound reliability. Statistical differences were found in most of the analysed anatomical sites (p < 0.001) except in biceps G2 (Z = -1.150, p = 0.25) and G3 (Z = -1.309, p = 0.19). Good correlations (r > 0.7, p ≤ 0.05) were reported at almost all anatomical sites and groups except for biceps (G1: Rho = 0.26, p = 0.140) and abdominal (G2: Rho = -0.16, p = 0.38; G3: Rho = 0.43, p = 0.068). Lin’s concordance correlation coefficient registered low values of agreement between skinfolds and A-mode ultrasound (ranged from—0.009–0.646). The scatterplot and the estimated regression line drawn through the midst of all anatomical sites of the whole sample had a slope of 0.51 and R2 adjusted = 0.62 was obtained. The combined analysis between the Bland-Altman plot and the linear regression showed that specifically in the G2 and G3 groups, as the SAT increases the differences between skinfolds and ultrasounds measurements also increases.ConclusionsThe Renco Lean-Meater ultrasound is not interchangeable with skinfold measures. Its utility is questionable, particularly for assessing SAT in active adult populations. Its poor test-retest and inter-rater reliability as well as the lack of agreement when compared to the skinfolds would exclude the free use of the A-mode ultrasound scanner in its hypothetical replacing of the classical calipers.

Why primary obesity is a disease?

“…The reliability of the folds is limited by several factors, such as the variability of the thickness of the subcutaneous adipose tissue, the inter-individual variability of the elastic properties of tissues and the impossibility of measuring too large skinfolds reduce accuracy, especially in the obese. Furthermore, a limitation is the assumption that the amount of subcutaneous fat reflects that of visceral fat [74].…”

Intra and Inter-rater Reliability between Ultrasound Imaging and Caliper Measures to determine Spring Ligament Dimensions in Cadavers

“…According to repeatability analyses 10–13 , our measurements showed good repeatability ( P -value > 0.05) for the SL dimensions by US (Table 7), caliper (Table 8) and comparison between both tools (Table 9) between inter-session first and second observers values, except for SL width dimension measured with US ( P -value = 0.019). Despite SL width dimensions should be considered with caution due to these US repeatability differences, to the authors’ knowledge, our study may be considered as the first research work providing reliability, absolute accuracy, correlation and repeatability for SL width dimension measured by US, due to prior US reliability studies mainly focused on SL length and thickness 5–8 .…”

“…Thus, given that there is existing literature correlating ultrasound measurements to clinical decisions and other imaging modalities 5–8 , absolute accuracy of the measurement needs to be determined due to the lack of studies about reliability and correlation between caliper and US measurements of the SL in cadaveric feet addressing width, thickness and length for a better accuracy of these evaluations and the improvement of ultrasound-guided procedures 9 . Both intra and inter-rater reliability needs to be detailed in order to determine absolute accuracy and repeatability of these measurements within a same evaluator and between both evaluators by both US and caliper 10–13 . Separately, both tools have shown appropriate reliability for SL dimensions measured by experienced raters, nevertheless US and caliper measures have not been compared as well as SL width dimensions have not yet been measured by US 5–8 .…”

Contrasting recruitment of skin-associated adipose depots during cold challenge of mouse and human

“…Fat-only images allow quantitative evaluation of fat content and SAF thickness, compared to the more standard fat/water MRI images (data not shown). This methodology is focused specifically on the fat content of skin, rather than the thickness of skin, which can be measured by skin fold calipers or ultrasound (Perez-Chirinos Buxade et al, 2018;Storchle et al, 2018). These other techniques are not designed to determine only the thickness of fat.…”