How to obtain the waist circumference for retrospective studies - a prospective validation of CT images for the evaluation of the abdominal perimeter

Transcription

1 How to obtain the waist circumference for retrospective studies - a prospective validation of CT images for the evaluation of the abdominal perimeter Poster No.: C-0281 Congress: ECR 2013 Type: Scientific Exhibit Authors: A. Ciudin 1, R. Salvador 1, A. Budoy 1, L. Bunesch Villalba 1, A. Ciudin 1, M. G. Diaconu 1, C. Spinu 2, C. Nicolau 1, A. Alcaraz 1 ; 1 Barcelona/ES, 2 Sabadell/ES Keywords: DOI: Abdomen, Computer applications, CT, Health policy and practice, Endocrine disorders, Metabolic disorders /ecr2013/C-0281 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 8

2 Purpose The waist circumference is one of the criteria used for the definition of the metabolic syndrome 1. It is also an independent cardiovascular risk factor, with higher predicting value than the body mass index 2. In retrospective studies it can be difficult to obtain the value of the waist circumference if this data was not specifically measured before. Moreover, as the waist circumference changes with time, it cannot be evaluated retrospectively. Abdominal CT images fulfill perfectly the purpose of saving a snapshot of the abdominal circumference of a person at a certain moment in time. An apparent limitation of this idea is the fact that abdominal CTs are performed in supine position and the abdominal perimeter is usually measured with the patient in standing position 3. Nonetheless, recent studies suggested that supine position can also be used with minimal differences 4. The objective of our study was to validate the use of supine position and abdominal CT images for the evaluation of waist circumference by demonstrating that the abdominal perimeter obtained from abdominal CT images is equivalent to the real-life measured waist circumference. Methods and Materials Prospective study in consecutive patients that underwent a programmed abdominal CT in our center between the 17 th and the 25 th of September The AC was measured 4 times: 1. standing position, 2. supine position on the CT table, 3. On CT images with a free-hand elliptical line following skin contour, using the OsiriX (Geneva, Switzerland) software. 4. On CT images using an ellipse perimeter formula, imputing antero-posterior and transverse abdominal diameters using the RAIM Alma 2010 (Barcelona, Spain) software. Page 2 of 8

3 In all patients a measurement of the abdominal circumference was performed both in standing and supine positions by the same nurse in a sequential mode, just before the abdominal CT. A Gulick type measuring tape was used. All patients underwent an abdominal CT that was indicated for diagnostic purpose. The study adheres to local regulations and standards and was approved by the Institutional Review Board. The abdominal circumference was evaluated on images right above the iliac crest, on the last slice, from cranial to caudal, not showing the iliac bone, thus imitating the algorithm used for the measurements performed in both standing and supine position. The measurements and estimations done in the cross-sectional images were performed blinded to the real waist circumference. The observers using the RAIM ALMA and the Osirix software were independent and blinded to each other's evaluations. Wilcoxon, Q-Q plot, and Bland-Altman analysis were used. Images for this section: Page 3 of 8

4 Fig. 1: Evaluation of the waist circumference on a CT image, using both a line to approximate the skin contour and calculating the antero-posterior and transverse abdominal diameters. Page 4 of 8

5 Results The study was proposed to 65 patients. Three patients denied participating. A total of 62 patients were included. The mean age was 61 years (range 32-75), the percentage of women was 36%. The mean BMI was 25 (range 18-39). The mean waist circumference was 93.4cm (range ). The results of the standing measurement compared with the supine one, the circumferential estimation on CT images and the ellipse perimeter estimation also on CT images can be found in the table. A QQ dispersion plot and a Bland-Altman analysis graph of standing versus ellipse perimeter waist circumference can be found in Figures 2 and 3. Standing vs. Supine Patients by AP Wilcoxon R2 Mean difference LOA All cm 4.0/-1.6cm cm cm 1.2/-0.4cm Circumferential All cm 4.5/-2.0cm Ellipse perimeter Images for this section: cm cm 1.3/-0.5cm All cm 4.2/-1.4cm cm cm 1.1/-0.3cm Page 5 of 8

6 Fig. 2: QQ plot of standing versus ellipse formula abdominal perimeters Page 6 of 8

7 Fig. 3: Bland-Altman plot of the differences between the standing and the ellipse formula abdominal perimeters Page 7 of 8

8 Conclusion Our study showed that for abdominal perimeters inferior to 110cm the supine and standing position measurements are equivalent. The estimation of the abdominal perimeter using either a circumferential line or the formula for the perimeter of an ellipse is also equivalent to the real abdominal perimeter measured in standing position. References 1. Alberti, K. G., Zimmet, P., and Shaw, J.: Metabolic syndrome--a new world-wide definition. A Consensus Statement from the International Diabetes Federation. Diabet Med, 23: 469, Janssen, I., Katzmarzyk, P. T., and Ross, R.: Body mass index, waist circumference, and health risk: evidence in support of current National Institutes of Health guidelines. Arch Intern Med, 162: 2074, Nishida, C., Ko, G. T., and Kumanyika, S.: Body fat distribution and noncommunicable diseases in populations: overview of the 2008 WHO Expert Consultation on Waist Circumference and Waist-Hip Ratio. Eur J Clin Nutr, 64: 2, Waninge, A., Ligthart, K. A., Kramer, J., Hoeve, S., van der Schans, C. P., and Haisma, H. H.: Measuring waist circumference in disabled adults. Res Dev Disabil, 31: 839, Personal Information Page 8 of 8