Validity of duplex scanning in the detection of peripheral arterial disease in the general population

Duplex scanning has the potential to identify asymptomatic atherosclerosis of the lower limbs in the general population. The aim of this study was to assess the validity of scanning in a group of men and women aged 55-74, sampled from a population survey. Disease was measured using the WHO questionnaire on claudication, the ankle brachial pressure index, and a reactive hyperaemia test. In 73 cases of peripheral arterial disease and 91 controls, a duplex scan was conducted on both legs from the inguinal ligament to the lower popliteal region. The two radiologists performing the scans were blind to the arterial status of the subjects. Interpretation of the image, waveform and peak systolic velocity resulted in a sensitivity of 78%, specificity of 65% and positive predictive value of only 19%. The image alone had the best positive predictive value (62%) and specificity (97%). These results suggest that duplex scanning may currently be of limited use as a diagnostic screening test in the general population. Interpretation of the image alone, however, may be useful in some settings in identifying healthy subjects free of disease.