Diagnostic performance of segmental plethysmography and Doppler ultrasound in obliterating vascular diseases in the lower limbs.

The diagnostic value of three noninvasive techniques was evaluated in a group of 100 "normal" and 100 "abnormal" limbs. The choice of segmental plethysmography, systolic pressure determination, and Doppler velocity curve was based on the fact that these methods are noninvasive, inexpensive, and atraumatic; they can easily be performed by paramedical personnel. There was a statistically significant difference between the ankle-to-arm systolic blood pressure ratio of normals and abnormals as measured by Doppler ultrasound with 0.96 as the dividing line, no false positives and only 11% false negatives were found. However, there was a large overlap for many parameters calculated from the velocity curve. The general morphological aspect of the velocity curve shows a better diagnostic performance than the calculated parameters of this curve: a monophasis curve had an 85% chance of being normal. The ankle segmental plethysmogram yielded only 5% false negatives, but 20% false positives; moreover, a biphasic curve has a 90% chance of being normal. Thus large-scale screening in clinical practice or in epidemiologic studies can best be done by Doppler pressure measurements; the velocity curve performs less satisfactorily. Segmental plethysmography is more sensitive, but it yields more false positive results.