A duplex criterion for aorto-iliac stenosis.

Duplex scanning is a new non-invasive test, which enables direct evaluation of aorto-iliac stenoses. The usual duplex criterion for an arterial stenosis is local increase in peak systolic velocity. For haemodynamically significant aorto-iliac stenoses a threshold value for this increase has not yet been established. In order to define a duplex criterion for significant aorto-iliac disease. The whole segment was scanned to locate areas with high peak systolic velocities which were then compared to the velocities recorded immediately up and downstream. The value of the highest proportional velocity change was used as the criterion for duplex classification of the segment. Duplex results were compared to the outcome of invasive femoral artery pressure measurements combined with reactive hyperaemia (FAP test). For a range of threshold values of the duplex criterion the specificity and sensitivity was calculated using the FAP test as the gold standard (R.O.C. analysis). The combinations of the highest sensitivity and specificity were obtained in the range of 100-200% change in peak systolic velocity as duplex criteria for significant aorto-iliac stenosis. The highest accuracy (88%) was obtained at a 200% change in the peak systolic velocity.