CoreScan is a new software for the GE Lunar iDXA, which provides a quantification of visceral adipose tissue (VAT). The objective of this study was to determine the in vivo precision of CoreScan for the measurement of VAT mass in a heterogeneous group of adults. Forty-five adults (aged 34.6 (8.6) years), ranging widely in body mass index (BMI 26.0 (5.2)  kg/m(2); 16.7-42.4 kg/m(2)), received two consecutive total body scans with repositioning. The sample was divided into two subgroups based on BMI, normal-weight and overweight/obese, for precision analyses. Subgroup analyses revealed that precision errors (RMSSD:%CV; root mean square standard deviation:% coefficient of variation) for VAT mass were 20.9 g:17.0% in the normal-weight group and 43.7 g:5.4% in overweight/obese groups. Our findings indicate that precision for DXA-VAT mass measurements increases with BMI, but caution should be used with %CV-derived precision error in normal BMI subjects.European Journal of Clinical Nutrition advance online publication, 15 October 2014; doi:10.1038/ejcn.2014.213

B Oldroyd

JL Kuk

JM Bland

K Hind

K Kishida

M G Mellis

MP Rothney

S Kaul

TE Carver

English

Mellis, MG

Oldroyd, B

Hind, K

Leeds Beckett Repository

1  In-vivo precision of the GE Lunar iDXA for the measurement of visceral adipose tissue in 1 adults: the influence of body mass index 2  3 Running title: Precision of the iDXA for the measurement of visceral fat 4  5 Michelle Grace Mellis1, Brian Oldroyd2, Karen Hind1  6  7 1 Carnegie Faculty, Leeds Metropolitan University, Headingley Campus, Leeds, LS6 3QT, UK.  8 2 Division of Medical Physics, University of Leeds, UK. 9  10 Corresponding author: Dr Michelle Mellis, Fairfax Hall 112, Leeds Metropolitan University, Headingley 11 Campus, Leeds, LS6 3QS. Tel: 0113 812 4010 Email: m.mellis@leedsmet.ac.uk  12  13 Conflict of Interest Statement: We declare that there is no conflict of interest 14 2  Abstract 15 CoreScan is a new software for the GE Lunar iDXA, which provides a quantification of visceral 16 adipose tissue (VAT). The objective of this study was to determine the in-vivo precision of CoreScan 17 for the measurement of VAT mass in a heterogeneous group of adults. 45 adults were recruited for 18 this study (age 34.6 (8.6) years), ranging widely in body mass index (BMI 26.0 (5.2) kg.m-2 (16.7 – 19 42.4 kg.m-2). Each participant received two consecutive total body scans with re-positioning. The 20 sample was divided into two sub-groups based on BMI, normal and overweight/obese, for precision 21 analyses. Sub-group analyses revealed precision (RMS-SD:%CV) for VAT mass were 20.9g:17.0% in 22 normal and 43.7g:5.4% in overweight/obese groups. Our findings indicate that the precision error for 23 VAT mass increases with increasing BMI but caution should be used with %CV derived precision 24 error in normal BMI subjects. 25  26   27 KEY WORDS: DXA; reproducibility; visceral fat; body composition28 3  Introduction 29 Clinical investigations have demonstrated close relationships between regional fat mass and disease 30 risk, mainly the association of trunk fat with the clustering of cardio-metabolic risk factors associated 31 with metabolic syndrome (1).  Abdominal obesity is also an independent predictor of all-cause 32 mortality (2). Computed tomography (CT) is the gold standard assessment of visceral adipose tissue 33 (VAT) but it is expensive and the high radiation exposure suggests the risks would outweigh the 34 benefits if used as a screening tool. Dual-energy X-ray absorptiometry (DXA) provides a precise 35 measurement of three compartment body composition (3). GE have recently introduced CoreScan; a 36 new tool for the quantification of VAT, which has been validated with CT in healthy men and women 37 (4). The advantages of using DXA over CT include the lower radiation exposure and greater time 38 efficiency.  39  40 It is important to determine in-vivo precision of all DXA measurements for interpretation of results 41 and patient monitoring. The purpose of this study was to ascertain the short term in-vivo precision of 42 the GE Lunar iDXA CoreScan software for the measurement of VAT mass in normal, overweight and 43 obese adults.   44  45 Materials/Subjects and Methods 46 Forty five men (n=10) and women (n=35) received two consecutive total body DXA scans with re-47 positioning, after providing signed informed consent to participate in the study approved by the 48 Institution’s Research Ethics Committee and in accordance with the Declaration of Helsinki.  49  50 Participants were measured wearing light weight clothing and all jewellery was removed. Height was 51 determined with a stadiometer (SECA, Birmingham, UK) to the nearest 0.1cm, and body weight was 52 recorded by calibrated electronic scales (SECA, Birmingham, UK) to the nearest 0.1kg. BMI was 53 calculated as body mass in kilograms/ height in metres squared. Scans were conducted on a fan-beam 54 GE Lunar iDXA using standard (153mm/sec) or thick (80mm/sec) mode depending on body stature. 55 Participants were placed in the supine position on the scanning table with the body aligned with the 56 4  central horizontal axis. Arms were positioned parallel to, but not touching the body. Forearms were 57 pronated with hands flat on the bed. Legs were fully extended and feet were secured with a canvas 58 and Velcro support to avoid foot movement during the scan acquisition. Each participant was re-59 positioned between scans, after dismounting the scanning table. One skilled technologist led and 60 analysed all scans following the manufacturer’s guidelines for patient positioning. Identical scanning 61 parameters were used for each scan. The regions of interest for the total body cut-offs were manually 62 adjusted according to the manufacturer’s instructions. The ROI over the android region for the 63 assessment of VAT was automated by the software. Scan analyses were performed using the Lunar 64 Encore software (Version 15). The machine’s calibration was checked and passed on a daily basis 65 using the GE Lunar calibration hydroxyapatite and epoxy resin phantom. There was no significant 66 drift in calibration for the study period.  67  68 Statistics 69 Data analysis was computed using Microsoft Excel 2010 and IBM SPSS Statistics software (Version 70 21). Participant descriptive data are reported as the mean and standard deviation (SD). The precision 71 error is represented as the square root of the mean of the sum of the squares of differences between 72 measurement 1 and measurement 2. The precision parameters, the root-mean-square standard 73 deviation (RMS-SD), %CV (RMS-%CV), intra-class correlation coefficient (ICC) and the resulting 74 least significant changes (LSC) were calculated manually. The %CV is derived from the equation: 75 %CV = (SD/mean value) * 100. 76 Bland Altman analysis was used to compare the paired measurements (5). 77  78 Results and Discussion 79 According to the World Health Organisation BMI guidelines, 4% participants were underweight 80 (n=2), 47% were classified as normal weight (n=21), 29% were overweight (n=13) and 20% obese 81 (n=9). For analysis, the underweight and normal weight category were combined to form the ‘normal 82 weight group’ (BMI = 22.1 (2.2) kg.m-2; Age = 33.2 (8.6); n=20 female; n=3 male) with a range of 83 5  16.7-24.9 kg.m-2; and the overweight and obese weight categories were combined to form a group 84 (BMI = 30.0 (4.4) kg.m-2; Age = 35.9 (9.0); n=15 female; n=7 male) with a rang of 25.5-42.4 kg.m-2.  85  86 The overweight/obese group had greater VAT mass (mean of two measurements - normal  87 : 123 (104)g; overweight/obese: 806.5 (564)g. Figure 1a and 1b illustrate Bland Altman VAT mass 88 analysis for the two  groups.  For the normal BMI groups, mean of the differences = -2.3 ± 30.2 with 89 limits of agreement -62.3g to 57.7g.  For the overweight/obese group mean of the differences = 15.9 ± 90 61.1g with limits of agreement  -106g to 138g was observed.  Although the mean of the differences 91 were small the range of inter-measurement differences increased with BMI. No magnitude effects 92 were observed from Bland Altman analysis. 93  94 Table 1 shows the VAT mass precision and LSC at 95%CI for both groups and precision values 95 determined from previous studies.  For RMS-SD precision values, the normal BMI groups have a 96 lower precision error: 20.9g but increased precision error with %CV: 17.0, compared to the 97 overweight/obese group, 43.7g and 5.4% respectively. This is due to %CV being dependant on its 98 inverse relationship with the mean value and in this study mean values of the two groups are different: 99 123g - 806g, resulting in the observed differences in %CV. Therefore the 95%CI derived from RMS-100 SD is the more reliable estimate. Our precision estimates for the overweight/obese group are in close 101 agreement with the obese group precision values determined by Rothery et al (6). In the study of 102 severely obese subjects by Carver et al (7) there is an marked increased in the RMS-SD precision 103 error but only a small increase in the %CV precision error compared to the obese subjects due to the 104 higher VAT mass mean value in the severely obese group.  105  106 We investigated precision error of the GE CoreScan VAT software in a heterogeneous sample of 107 adults. This sample was representative of the usual research participants who attend our DXA centre. 108 Using RMS-SD there was a small increase in the imprecision error with BMI in our study groups 109 (20.9g compared to 43.7g). The RMS-SD and %CV precision values for the overweight/obese are 110 similar to those reported by Rothney et al (6) due to the similar mean VAT masses. Our findings 111 6  differ to those of Carver et al (7) who reported a RMS-SD precision for a severely obese group of 112 294g. A limitation of the study is that the effect of gender could not be investigated due to the low 113 numbers of males. It should therefore provide a valuable avenue for future research.  114  115 We, and others, have previously reported excellent in vivo precision for iDXA measurements of total 116 fat mass and total lean mass, regardless of BMI (3, 8). As suggested elsewhere, the visceral region is 117 relatively small and the mathematical complexities to distinguish VAT from subcutaneous fat may 118 lead to greater precision error (6). In conclusion, iDXA CoreScan provides good precision for VAT 119 measurements for individuals with a BMI between 25.5 – 42.4 kg.m-2, This study and comparisons 120 with previous studies also highlights that the %CV value for precision should not be used when study 121 population mean vales differ as observed in this study. 122  123 References 124 1. Kishida K, Funahashi, T, Matsuzawa Y, Shimomura I. (2012) Visceral adiposity as a target for 125 the management of the metabolic syndrome. Ann Med 2012; 44: 233-241. 126 2. Kuk JL, Katzmarzyk PT, Nichaman MZ, Church TS, Blair SN, Ross R. Visceral fat is an 127 independent predictor of all-cause mortality in men. Obesity 2006; 14: 336-341. 128 3. Hind K, Oldroyd B, Truscott J. In-vivo short term precision of the GE Lunar iDXA for the 129 measurement of three compartment total body composition in adults. Eur J Clin Nutr 2011; 65: 130 140-142. 131 4. Kaul S, Rothney MP, Peters DM, Wacker WK, Davis CE, Shapiro MD et al. Dual-energy X-ray 132 absorptiometry for quantification of visceral fat. Obesity 2012l 20:1313-1318. 133 5. Bland JM, Altman DG. Comparing two methods of clinical measurement: a personal history. Int J 134 Epidemiol 1995; 24: S7-14. 135 6. Rothney MP, Xia Y, Wacker WK, Martin FP, Beaumont M, Rezzi S et al. Precision of a new tool 136 to measure visceral adipose tissue (VAT) using dual-energy X-ray absorptiometry (DXA). 137 Obesity 2013; 21: E134-E138. 138 7  7. Carver TE, Court O, Christou NV, Reid RER, Andersen RE. Precision of the iDXA for visceral 139 adipose tissue measurement in severely obese. Med Sci Sports Exerc 2004; e-pub ahead of print 140 25 November 2013; doi:10.1249/MSS.0000000000000238. 141 8. Oldroyd B, Smith AH, Truscott JG. Cross calibration of GE/Lunar pencil and fan beam dual 142 energy densitometers – bone mineral density and body composition studies. Eur J Clin Nutr 2003; 143 57: 977-987. 144  145  146 Table Legends 147 Table 1: Precision comparison between two separate measurements of VAT mass. 148  149 Figure Legends 150  151 Figure 1: Bland-Altman plot between two measurements of VAT mass in the a) normal BMI group 152 and b)  the overweight and obese group 153  154 155 8  Table 1 156 BMI Classification n BMI (kg/m2)  Vat  Mass (g) RMS-SD(g) %CV      LSC(95%CI)  LSC(95%CI) Normal* 23 (20f/3m) 22.1(2.2) 123 20.9 59.1 17.0 48.1 Overweight/Obese* 22 (15f /7m) 30.0(4.4) 806 43.7 123.6 5.4 15.3 Obese (6) 32f 35.1(3.1) 1110 56.8 160.7 5.1 14.4 Severely Obese (7) 55(36f/19m) 49.0(6.0) 3250 294.0 832.0 8.7 24.9  157 *Mellis et al (2014) - current study results KEY: RMS-SD - Root Mean Square of the Successive Differences; CV - Coefficient of Variation; LSC 95% CI - Least Significant Change at 95% Confidence Intervals   158 159 9  0 100 200 300 400 500-200-150-100-50050100150200Difference in paired VAT Mass (g)Mean paired VAT Mass (g)mean = -2.3g LOA = 57.7gLOA = - 62.3gFig 1 a 160  161 0 500 1000 1500 2000-200-150-100-50050100150200Differences in paired  VAT Mass (g)Mean paired VAT Mass(g)mean = 15.9gLOA = 138gLOA = -106gFig 1b 162 

In vivo precision of the GE Lunar iDXA for the measurement of visceral adipose tissue in adults: the influence of body mass index.

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European Journal of Clinical Nutrition

In vivo precision of the GE Lunar iDXA for the measurement of visceral adipose tissue in adults: the influence of body mass index

CoreScan is a new software for the GE Lunar iDXA, which provides a quantification of visceral adipose tissue (VAT). The objective of this study was to determine the in vivo precision of CoreScan for the measurement of VAT mass in a heterogeneous group of adults. Forty-five adults (aged 34.6 (8.6) years), ranging widely in body mass index (BMI 26.0 (5.2)  kg/m2; 16.7–42.4 kg/m2), received two consecutive total body scans with repositioning. The sample was divided into two subgroups based on BMI, normal-weight and overweight/obese, for precision analyses. Subgroup analyses revealed that precision errors (RMSSD:%CV; root mean square standard deviation:% coefficient of variation) for VAT mass were 20.9 g:17.0% in the normal-weight group and 43.7 g:5.4% in overweight/obese groups. Our findings indicate that precision for DXA-VAT mass measurements increases with BMI, but caution should be used with %CV-derived precision error in normal BMI subjects

Mellis, M. G.

Oldroyd, B.

Hind, K.

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In vivo precision of the GE Lunar iDXA for the measurement of visceral adipose tissue in adults:the influence of body mass index

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In vivo precision of the GE Lunar iDXA for the measurement of visceral adipose tissue in adults: the influence of body mass index.

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