Sources of error in Doppler diagnosis of carotid occlusive disease.

Fifty errors with Doppler examination of 356 carotid bifurcations were examined to determine their cause and to establish methods of prevention. Only those errors related to hemodynamically significant stenosis or complete occlusion were considered. The relative frequency of errors in diagnosis of occlusion (30 false-positive or negative versus 31 true-positive) was considerably greater than the rate of inaccuracy for diagnosis of hemodynamically significant stenosis (20 false-positive or-negative versus 89 true-positive). The high error rate in diagnosis of occlusion was attributed to reliance on negative information. The source of error could be established in 48 of the 50 cases. In all but three cases, potential for preventing error existed through use of additional noninvasive techniques such as examination of common carotid resistivity or use of oculoplethysmography. Twenty-two errors of localization of stenosis or occlusion were encountered in addition to the 50 false-positive and -negative errors. In three of these, the errors might have led to patient mismanagement.