This pilot study compared measurements of the aorta and the velocity measurements and presence of plaque in the carotid arteries.
Measurements were made of aortic dimensions, carotid Doppler velocities and the presence or absence of plaque.
The objective was to see how closely Life Line Screening's measurements, and therefore our ability to detect disease, matched those of a world class tertiary care ICAVL accredited vascular laboratory. In other words, the primary purpose was to determine the degree of agreement between measurements of both parties.
For the carotid studies The Cleveland Clinic Foundation (CCF) used Kappa statistics. Kappa is a general purpose parallel database management system, used expecially for knowledge information processing by researchers.
Kappa has three (3) levels used for comparison of data:
- Less than .40 = poor agreement
- .40 to .75 = good agreement
- Greater than .75 = excellent agreement
For the aorta study the conclusion was "remarkably good agreement was found except for the middle aortic segment where CCF measurements were systematically 2mm greater than the screening company." (This is due to the fact that LLS measurements are taken at a point more distal than theirs and is simply a variation in protocols that is quite typical.) According to CCF, these differences (2mm is very tiny) were not of the magnitude to raise concerns regarding clinical consequences. AORTA MEASUREMENT RESULTS: remarkably good agreement.
For the carotid study, both parties identified a fairly high prevalence of carotid plaque and demonstrated an excellent degree of agreement. For the comparison of the presence or absence of carotid plaque, the Kappa statistic was caculated.
For the RICA (right internal carotid artery) the Kappa = .82, 95% CI .64 to 1.01.
For the LICA (left internal carotid artery) the Kappa = .79, 95% CI .59 to .98.
CI means Confidence Interval. It represents the probability of reproducing the same results over and over again. So for the RICA with a Kappa of .82 (excellent agreement, look above at the Kappa levels) 95% CI .64 to 1.01, this means that for the RICA, which showed excellent agreement, if we were to perform the exact same studies again 100 times, 95% of the time the Kappa would fall between .64 and 1.01. With a Kappa of .82 and .79 the agreement was in the excellent range, and along with that so was the likelihood of reproducibility.
This study does not address the issue of whether of not mass screening is worthwhile, but does show that the quality of measurements and, therefore the identification of disease, may be quite acceptable and comparable to accredited vascular labs.
