Observer variability in evaluating extracranial carotid artery stenosis.

Abstract

ANGIOGRAPHY AND CAROTID ULCERATION/ErteSUMMARY One hundred twenty eight cervical carotid arteriograms were twice viewed by three readers for the evaluation of atherosclerotic disease at the carotid bifurcation. Stenoses were estimated using calipers to the nearest 5% and lesions were qualitatively characterized as smooth, irregular, or ulcerated. The intraobserver correlation coefficient between estimates of percent stenosis was .94 overall and .98 for the internal carotid artery. The average intraobserver variability in estimating percent stenosis was 5.23% for all vessels and 6.04% with a standard deviation of 8.09% for the internal carotid artery. The intraob server percent agreement at a fixed stenosis is denned as the percent of the time one reader on two readings would read at least the fixed percent stenosis among cases that might be read as having the fixed percent stenosis. The intraobserver percent agreement rate for the internal carotid artery was 95.9% at > 0% stenosis, 90.4% for 50% or greater stenosis, and 96.8% for 100% stenosis (total occlusion). The interobserver correlation coefficient between readers was .92 overall and .97 for the internal carotid artery. The absolute difference in percent stenosis between readers was 7.21% for all vessels and 8.64% for the internal carotid artery with a standard deviation of 9.5%. The interobserver agreement rate for the internal carotid artery at > 0% stenosis was 93.0%, 85.4% for 50% or greater stenosis and 96.8% at 100% stenosis. The addition of oblique views had no statistical effect on estimates of percent stenosis but increased the frequency with which irregularity and ulceration were diagnosed in the internal carotid artery. Stroke Vol 14, No. 6, 1983CEREBRAL ANGIOGRAPHY remains the major di agnostic tool in evaluating symptomatic patients with extracranial occlusive disease and is also used as a reference standard for evaluating newer noninvasive diagnostic modalities.1-12 Although major patient man agement decisions and evaluations of new techniques and equipment are based on angiographic interpreta tions, no detailed statistical analysis of observer vari ability has been performed. This study was designed to assess this variability and in addition to evaluate the contribution of oblique views to the characterization of stenotic lesions of the carotid bifurcation. Materials and MethodsThe angiograms of 100 consecutive patients who underwent cerebral angiography which included serial biplane filming of the cervical carotid arteries were reviewed. From this population, 64 cases were select ed on the basis of having AP, lateral and two oblique views of each carotid bifurcation which were of suffi cient technical quality to permit careful evaluation un der normal viewing conditions. AP and lateral films were obtained on 10 by'12 inch Schonander changers with the patient supine. The patient was then rotated en bloc 20 degrees away from the side of the catheter and the filming repeated producing "AP" and "lateral" oblique views. The 20 degree angle of ro...

Distribution and correlates of sonographically detected carotid artery disease in the Cardiovascular Health Study. The CHS Collaborative Research Group.

“…Studies of the variability associated with measurement of stenosis by ultrasound or angiography have shown that within-and between-observer agreement is better when arteries are normal or highly diseased and worse when they are mildly or moderately diseased. 37 - 38 Our results demonstrate that the majority of elderly subjects have mild disease. Also, wall thickness measurements are continuous variables as opposed to stenosis categories.…”

Measurement variability of carotid atherosclerosis: real-time (B-mode) ultrasonography and angiography.

“…In the largest study of carotid angiography reported, Chikos et al 5 found a similar degree of within-and between-reader variability in estimates of percent stenosis; their 64 cases were drawn from a larger set of 100 consecutive patients, 36 of whom were excluded because of relatively poor technical quality. All studies were selective arterial injections; the single best opacified view from each projection was preselected, and each reader was given the same set of films.…”

Critical Appraisal of the Design and Reporting of Studies of Imaging and Measurement of Carotid Stenosis

“…Of the resulting sample of 162 studies, 93 were published before 1991 and 69 were published between 1993 and 1997. Twenty studies from each period were randomly selected for detailed review (1970 -1991 [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] and 1993-1997 [45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64]. No studies by any of the authors were selected, and thus there was no conflict of interest.…”