Carotid Intima-Media Thickness (CIMT): A Reproducibility Study
Mindy Columbus, Brian Wagner, Emma Barinas-Mitchell
Department of Epidemiology, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
Introduction
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.
Hypothesis
The null hypothesis is that there is no difference
in CIMT between the Toshiba and Antares
Doppler ultrasound machines.
Siemens Sonoline® Antares
Toshiba 140A
The Ultrasound Research Lab (URL) in the
Department of Epidemiology performs
subclinical cardiovascular disease testing for
many NIH funded population-based studies.
Certification Reads – Tech 1 vs. Tech 2
Antares vs. Toshiba Reads
Conclusion
A 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.
References
Methods
Summary of Training:
Carotid duplex scanning
Reading carotid scans
Certification in reading of scans
Reading for reproducibility study
Study Design:
Volunteers recruited for carotid duplex scanning
Tech 1 = Certified URL sonographer
Tech 2 = Mindy Columbus
Question
In 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.
Results
Mean Difference = 0.015
Mean absolute difference = 0.022
Standard Deviation = 0.024
Range = -0.022 to 0.049
Spearman correlation (r=0.98, p<.0001)
ICC = (0.02549/0.0257512 = .99)
www.nhlbi.nih.gov
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.
Statistical Analyses:
Intraclass correlation (ICC) is an estimate of the
degree of total measurement variability caused by
between individual variation.
Mean Difference = -0.045
Mean absolute difference = 0.052
Standard Deviation = 0.063
Range = -0.256 to 0.077
Spearman correlation (r=0.93, p<.0001)
ICC = (0.02534/0.0282651 = 0.896)
20
Volunteers
Toshiba
Tech 1
(scan)
Toshiba
Tech 1
(read)
Toshiba
Tech 2
(read)
Study Population:
N=20
Females = 17 (85%)
Males = 3 (15%)
Age Range = 24 – 77 years
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
*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.
Antares
Tech 1
(scan)
Antares
Tech 1
(read)
obs
Antares
Tech 2
(read)
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Acknowledgements
We would like to thank the staff of the Department
of Epidemiology Ultrasound Research Lab for the
training and resources used to conduct this study.