Allen's test is useful in evaluating

The Allen test can detect the patency of both radial and ulnar aeries (aeries forming the palmar arch) Method The pt. squeezes his hand to express the blood and then both aeries are compressed by the examiner's fingers - the hand turns white Now pressure on one aery is removed and the change in color of hand noted : if the aery is blocked the colour remains white if it is patent, the palm assumes the normal colour Now the test is repeated and the pressure removed from the other aery, to check its integrity.