One hundred fifty individuals of different ages without evidence of peripheral vascular impairment (100 normal persons and 50 patients with history of cerebral vascular disease) were examined with the Allen test; the radial and ulnar arteries were examined in both hands. A false-positive test could easily be obtained spontaneously or be provoked by intentional hyperextension of the hand more than 20° beyond the straight position. In the straight position of the hand, the time for appearance of rubor after opening of the hand exceeded 5 seconds in 34% of the normal persons. When a relaxed slight flexion at the wrist joint was used, the flush after opening the hand appeared at an average of 3 seconds for the ulnar artery and 2.75 for the radial artery. In 50 normal individuals examined with optimal technique described, no individual artery required more than 6 seconds for the flush to appear after opening of the hand. The authors recommend that the Allen test be performed with the patient's hand slightly flexed and relaxed.

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