Validity of a portable computerbased ultrasound ...

Clin Physiol Funct Imaging (2014)

doi: 10.1111/cpf.12146

SHORT COMMUNICATION

Validity of a portable computer-based ultrasound system for estimating adipose tissue in female gymnasts Jeremy P. Loenneke1, Jeremy T. Barnes2, Jason D. Wagganer2 and Thomas J. Pujol2 1

Department of Health and Exercise Science, University of Oklahoma, Norman, OK, and 2Department of Health, Human Performance, and Recreation, Southeast Missouri State University, Cape Girardeau, MO, USA

Summary Correspondence Jeremy Paul Loenneke, 1401 Asp Avenue, Room 104, Norman, OK 73019-0615, USA E-mail: [email protected]

Accepted for publication Received 24 October 2013; accepted 27 February 2014

Key words adipose tissue; athlete; body fat; composition; fitness; imaging; skinfolds; ultrasound

The aim of this investigation was to determine the validity of a portable ultrasound instrument for estimating adipose tissue (AT%) compared to dual-energy X-ray absorptiometry (DXA) in female collegiate gymnasts. Participants had their measurements taken in the following order: urine-specific gravity, body mass, height, ultrasound determined AT% (1-site and 3-site) and DXA determined AT%. The current pilot study found significant differences between estimates of AT% (P < 0001). Pearson’s correlations between DXA and 1-site and 3-site estimates were r = 0786 and r = 0753, respectively. The standard error of the estimate between DXA and 1-site and 3-site estimates was 36% and 39%, respectively. However, the average deviation of individual scores from the line of identity was 67% for the 1-site and 49% for the 3-site, when compared with the DXA estimate. The results of this preliminary study found that the portable ultrasound was not a valid estimate of AT% when compared with the DXA estimate in female collegiate gymnasts.

Introduction

Methods

When health professionals measure the fitness levels of athletes, body composition is usually estimated. Recently, a portable computer-based ultrasound instrument for estimating what percentage of body mass is composed of adipose tissue (AT%) has become available commercially. A reported advantage of using this ultrasound system is that inter- and intrarater variations may be minimized when compared with the skinfold technique (Ulbricht et al., 2012). However, this may not be true, as a recent study found that this portable ultrasound instrument may not be valid when compared with a professional with experience using the skinfold technique (Loenneke et al., 2014). Other than the aforementioned study, only three other studies have investigated the correlation of this method with skinfolds and BIA (Utter & Hager, 2008; Johnson et al., 2012; Ulbricht et al., 2012) with respect to AT%, but more advanced validity statistics were not performed in two of those investigations (Johnson et al., 2012; Ulbricht et al., 2012). Therefore, the purpose of this pilot study was to determine the validity of a portable ultrasound instrument compared to dual-energy Xray absorptiometry (DXA) in female collegiate gymnasts (National Collegiate Athletic Association, Division 1).

Thirteen female gymnasts volunteered to participate in this pilot study. Participants [20 (1) years.; 16 (01) m; 629 (76) kg] attended the laboratory on one occasion and were thoroughly informed of the purpose, nature, practical details and possible risks associated with the experiment, as well as the right to terminate participation at will, before they gave their voluntary informed consent to participate. The study was approved by the university’s institutional review board. Participants had their measurements taken in the following order: urine-specific gravity (USG), body mass, height, ultrasound determined AT%, and DXA determined AT%.

Instrumentation DXA The participants’ criterion body composition was estimated using a GE Lunar Prodigy DXA machine (GE Healthcare, Pewaukee, WI, USA). Before testing, a quality assurance phantom was performed and passed. Before each test, height was measured to the nearest cm using a wall-mounted

© 2014 Scandinavian Society of Clinical Physiology and Nuclear Medicine. Published by John Wiley & Sons Ltd

1

2 Ultrasound estimated body composition, J. P. Loenneke et al.

standiometer, and body mass was measured using an electronic scale (Tanita BF-350, Arlington Heights, IL, USA). Participants lay supine on the DXA table with their hands lying flat and pronated and asked to remain motionless while their body was scanned. Ultrasound The participant’s body composition was estimated using a portable computer-based BodyMetrix Pro BX2000 ultrasound system (IntelaMetrix, Livermore, CA, USA). Prior to testing, the system was calibrated according to manufacturer guidelines. The sites for 3-site assessments are identified in the user’s guide as thigh, tricep and suprailiac for females, whereas the 1-site method utilizes the bicep brachii only. These sites were located by utilizing the guidelines published by the American College of Sports Medicine (American College of Sports Medicine et al., 2010). Participants stood while all the measurements were taken and all measurements were taken on the right side of the body. The same researcher conducted all the ultrasound assessments. Urine-specific gravity Although normal fluctuations in hydration are no longer thought to have a large effect on the DXA estimate of body composition, hydration status was confirmed using a digital hand-held USG refractometer (PEN-Wrestling, Atago, Tokyo, Japan). Statistical analyses All descriptive and repeated measures ANOVA data are represented as means and standard deviations (SD). Post hoc pairwise comparisons were made with paired sample t-tests Bonferroni adjusted for the number of comparisons made. The validity of the AT% estimates was based on the evaluation of each method versus the estimated value from DXA by calculating the mean, SD, Pearson’s correlation and standard error of estimate (SEE) from linear regression analysis. To assess the average deviation of individual scores from the line of identity, total error (TE) was calculated for each field method.

Results The repeated measures ANOVA found significant differences between the estimates of AT% (P < 0001) (Table 1). Pearson’s correlations between DXA and 1-site and 3-site estimates were r = 0786 and r = 0753, respectively. The SEE between DXA and 1-site and 3-site estimates was 36% and 39%, respectively. The average deviation of individual scores from the line of identity was 67% for the 1-site and 49% for the 3-site, when compared with the DXA estimates. Mean USG was 1018 (0005) ranging from 1011 to 1029.

Table 1

The mean value of adipose tissue percentage (AT%).

Mean SD

DXAa

3-Siteb

1-Sitec

216 57

250 44

273 36

DXA, dual-energy X-ray absorptiometry; 1- and 3-site portable ultrasound system. Means with different letters denote significant differences between estimates.

Discussion The current pilot study found that the ultrasound was not a valid estimate of AT% in female gymnasts when compared with the DXA estimate (TE > 4%). Although the 3-site estimate appeared to be better than the 1-site estimate of AT%, both estimates were significantly different from the DXA estimate. In addition, the TE exceeded the 4% threshold of what is considered acceptable in body composition research (Heyward & Wagner, 2004). With respect to AT%, the specific ultrasound used in this study had only been investigated on three other occasions, but had never been compared to the DXA. Thus, the current study appears to be novel with respect to using an athletic population as well as a lab based criterion method (DXA versus BIA). For example, Johnson et al. (2012) compared the ultrasound estimate of AT% to the estimate from BIA and air-displacement plethysmography (ADP). They found that the ultrasound had high correlations with the BIA (r = 0862) and ADP (r = 0879). Ulbricht et al. (2012) compared the ultrasound estimate of AT% to skinfolds in normal and overweight participants. The only significant correlation for AT% was found in the overweight group (r = 050). In addition, a recent study from our laboratory found low correlations for both the 1-site and 3-site estimate of AT% compared to a skindfold estimate in college students (Loenneke et al., 2014). Further, the average deviation of individual scores from the line of identity exceeded 4%. Thus, it was suggested that the ultrasound device may not be a valid estimate of AT% when compared with skinfolds (TE > 8%). However, it is noted that Utter & Hager (2008) found that this ultrasound device provided similar estimates of fat-free mass when compared with underwater weighing in high school wrestlers. In conclusion, the results of this preliminary study suggest that the portable ultrasound was not a valid estimate of AT% when compared with the DXA estimate in female collegiate gymnasts. Although there is not a true gold standard in body composition, DXA is being increasingly recognized as a valid criterion estimate. However, it is possible that the results may be different if the current ultrasound device was compared to an underwater weighing estimate of AT%.

Acknowledgments The authors are not aware of any affiliations, memberships, funding or financial holdings that might be perceived as


Ultrasound estimated body composition, J. P. Loenneke et al. 3

affecting the objectivity of this manuscript. This study was not supported by any funding.

Author contributions

Conflict of interest

JPL developed study, analysed data, wrote and edited manuscript. JTB developed study, edited manuscript and collected data. JDW developed study, edited manuscript and collected data. TJP developed study and edited manuscript.

The authors report no conflict of interest.

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