Carotid Intima-Media Thickness (CIMT): A Reproducibility StudyCarotid Intima-Media Thickness (CIMT): A Reproducibility StudyMindy Columbus, Brian Wagner, Emma Barinas-Mitchell

Department of Epidemiology, University of Pittsburgh, Pittsburgh, Pennsylvania 15260

Coronary heart disease is the leading cause of death in America today, and caused 869,724 deaths in 2004.Coronary heart disease is caused by atherosclerosis, the narrowing of coronary arteries due to fatty build ups of plaque.CIMT is a well established surrogate marker of atherosclerosis and a predictor of cardiovascular disease events.CIMT is a valid and reproducible measure of subclinical cardiovascular disease.

www.nhlbi.nih.gov

The Ultrasound Research Lab (URL) in the Department of Epidemiology performs subclinical cardiovascular disease testing for many NIH funded population-based studies.

Digitized images are captured in real time using transverse and longitudinal views of the near and far walls of the distal CCA and the far wall of the bulb and ICA.CIMT is calculated as the average of the intima media thickness layers across the 8 segments to obtain the mean average CIMT.

IntroductionIntroduction

ReferencesReferences1. Chambless, L. et al. Risk Factors for Progression

of Common Carotid Atherosclerosis: The Atherosclerosis Risk in Communities Study, 1987-1998. American Journal of EpidemiologyAmerican Journal of Epidemiology. 2002;155:38-47.

2. de Groot E. et al. Measurement of carotid intima-media thickness to assess progression and regression of atherosclerosis. Natural Clinical Practice. Cardiovascular Medicine. 2008 May;5(5):280-8.

3. Sekikawa A. et al. Less Subclinical Atherosclerosis in Japanese Men in Japan than in White Men in the United States in the Post-World War II Birth Cohort. American Journal of Epidemiology. 2007;165:617-624.

4. Sutton-Tyrrell, K. et al. Measurement Variability in Duplex Scan Assessment of Carotid Atherosclerosis. Stroke. 1992, 23:215-220.

5. Thompson, T., Sutton-Tyrrell, K., Wildman, R. 2001. Continuous Quality Assessment Programs Can Improve Carotid Duplex Scan Quality. The Journal of Vascular Technology 25(1):33-39.

ResultsResults

Methods Methods Summary of Training:Carotid duplex scanningReading carotid scansCertification in reading of scansReading for reproducibility study

Study Design:Volunteers recruited for carotid duplex scanningTech 1 = Certified URL sonographerTech 2 = Mindy Columbus

Study Population:N=20Females = 17 (85%)Males = 3 (15%)Age Range = 24 – 77 years

HypothesisHypothesis

The null hypothesis is that there is no difference in CIMT between the Toshiba and Antares Doppler ultrasound machines.

QuestionQuestionIn the Department of Epidemiology Ultrasound Research Lab (URL), participants of the ERA JUMP study are returning for a five year follow-up visit for CIMT measurements to determine progression rates of subclinical atherosclerosis.A Toshiba 140A Doppler ultrasound scanner was used for the baseline measurements, and the question is whether the follow-up measurements can be taken on a Siemens Sonoline® Antares Doppler ultrasound scanner in order to predict progression and not to introduce error due to differences in machines.

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Mean Difference = -0.045Mean absolute difference = 0.052Standard Deviation = 0.063Range = -0.256 to 0.077Spearman correlation (r=0.93, p<.0001)ICC = (0.02534/0.0282651 = 0.896)

ConclusionConclusionA five year mean CIMT progression rate of ~0.04 mm was estimated based on the literature1. Since the mean absolute difference was 0.052 mm a difference in progression may be difficult to detect, and may in fact appear that the participant’s mean CIMT has improved. There was a difference between the machines, and a presence of systematic bias illustrated thicker CIMT reads with the Toshiba machine. This is likely due to the fact that the Antares scanner produces a crisper and clearer image demonstrating advancement of newer digitial technology. Based on these results, we conclude that the implementation of newer ultrasound technology may adversely affect the validity of progression data for follow-up studies that utilized the older technology for baseline measurements of CIMT.

AcknowledgementsAcknowledgementsWe would like to thank the staff of the Department of Epidemiology Ultrasound Research Lab for the training and resources used to conduct this study.

Siemens Sonoline® Antares

Toshiba 140A

Statistical Analyses:Intraclass correlation (ICC) is an estimate of the degree of total measurement variability caused by between individual variation.

Certification Reads – Tech 1 vs. Tech 2

Mean Difference = 0.015 Mean absolute difference = 0.022Standard Deviation = 0.024Range = -0.022 to 0.049Spearman correlation (r=0.98, p<.0001)ICC = (0.02549/0.0257512 = .99)

Antares vs. Toshiba Reads

*mavga = average CIMT Antares, *mavgt = average CIMT Toshiba, *dmavgat = difference of average CIMT between Antares and Toshiba

There is a presence of systematic bias in the statistics for the Antares vs. Toshiba comparison depicting thicker reads of CIMT with the Toshiba than with the Antares.

20 Volunteers

AntaresTech 1(scan)

ToshibaTech 1(read)

ToshibaTech 1(scan)

ToshibaTech 2(read)

AntaresTech 1(read)

AntaresTech 2(read)

obs urlid mavga mavgt dmavgat

1 70237 0.57444 0.83000 -0.25556

2 70256 0.68844 0.83469 -0.14625

3 901206 0.67756 0.73613 -0.05856

4 70136 0.62219 0.67969 -0.05750

5 901017 0.89131 0.94500 -0.05369

6 901136 0.60000 0.65069 -0.05069

7 70047 0.56369 0.61381 -0.05012

8 70223 0.55294 0.60088 -0.04794

9 901205 0.48875 0.53581 -0.04706

10 901208 0.52313 0.55294 -0.02981

11 70208 0.62138 0.64950 -0.02812

12 901069 0.63506 0.66281 -0.02775

13 71025 0.55350 0.58038 -0.02687

14 70105 0.76575 0.79213 -0.02638

15 901209 0.49069 0.51500 -0.02431

16 901122 0.49575 0.51600 -0.02025

17 70043 0.96831 0.98056 -0.01225

18 70148 0.86669 0.87731 -0.01062

19 71062 1.03038 1.03925 -0.00887

20 901125 0.90531 0.82863 0.07669