Main menu
hills_wide.jpg

THE SENSITIVITY, SPECIFICITY AND ACCURACY OF A SCREENING CAROTID EXAMINATION COMPARED TO A FORMAL CAROTID STUDY

Author Block M Matangi, D Armstrong, U Jurt, A Johri, D Brouillard

Kingston, Ontario

Abstract:
BACKGROUND: We have been performing full carotid studies for 7 years and screening carotid examinations for the past 2 years. The purpose of this study was to assess the accuracy of a screening carotid examination performed at the time of a routine ECHO with a formal carotid Doppler examination.
METHODS: A screening carotid examination was performed at the time of a routine ECHO in patients who were Statin naive and who had no prior evidence of vascular disease. The screening carotid examination includes 2-3 images of each carotid artery to include the common carotid artery (CCA), carotid bulb and internal carotid artery (ICA). A formal carotid Doppler examination may contain as many as 50-60 images along with continuous wave Doppler recordings. CCA IMT was measured in the far wall offline using an automatic edge detection program. Carotid plaque was defined using the ARIC criteria as either absent or present. A t-test was performed to assess differences between mean values. Sensitivity, specificity and accuracy were calculated. A Bland-Altman plot was used to assess agreement between the two methods of calculating CCA IMT. Linear regression was performed on an EXCEL scattergram to calculate the correlation coefficient.
RESULTS: There were 200 patients (108 males and 92 females) who underwent both the screening and the formal carotid examination within 30 days of each other. The mean age was 64.3 ± 10.3 years. Sixty-three percent of the screening and formal carotid studies were performed on the same day and 80% were within 1 week of each other. The mean maximal CCA IMT was 1.21 ± 0.56mm for the screening carotid and 1.23 ± 0.58mm for the formal carotid Doppler, (P=0.6935). The sensitivity, specificity and accuracy of the screening carotid examination were 96.8%, 100% and 97.5% respectively. The correlation coefficient was 0.97. The Bland-Altman scattergram below shows good agreement between the two studies with 95% of points being within ±1.96 SD.
CONCLUSION: A screening carotid examination as described above is an acceptable alternative for the detection of carotid atherosclerosis and maximal CCA IMT measurement. We believe such a screening examination can replace a formal carotid examination to help classify a patient's cardiovascular risk, especially those who are low or intermediate risk using the Framingham risk score.
Sensitivity, specificity and accuracy
  FORMAL CAROTID  
Plaque present Plaque absent
SCREENING CAROTID Plaque present 150 0 100% PPV
Plaque absent 5 45 90% NPV
  Sensitivity 96.8% Specificity 100% Accuracy 97.5% .