Value of color flow duplex imaging in detection of subtotal and total internal carotid artery occlusion

The aim of this retrospective study was to estimate the predictive value of color flow duplex imaging (CFDI) in the detection of near-total and total internal carotid artery (ICA) occlusion. The authors reviewed all diagnoses of 95-99% ICA stenosis and ICA occlusion made by CFDI from 1991 to 1994 at St. Mary's Hospital. One hundred thirty-seven patients with CFDI diagnosis of ICA occlusion and 42 with 95-99% stenosis had also been subjected to intraarterial digital substraction angiography during the same period and within one month from the CFDI. They compared the results of both methods to estimate the positive predictive value (PPV) of CDFI in the detection of ICA occlusion and 95-99% stenosis. Furthermore, they compared the PPV of CDFI diagnoses during 1991-1993 with that of 1994 for the same spectrum of ICA disease. CFDI had 96% PPV in the diagnosis of carotid seclusion (95% confidence interval, 94-97.9%, false-positive rate 3.6%) and 83% in the diagnosis of 95-99% stenosis (95% confidence interval 63.4-88.9%, false-positive rate 17%). Although there was improvement of CFDI's ability in the diagnosis of occlusion during 1994 in comparison with the 1991-1993 period, this was not statistically significant (PPV 95.9% and 97.4% respectively). CFDI may slightly underestimate or overestimate the degree of tight ICA stenosis. However, in the diagnosis of ICA occlusion CFDI is highly reliable.