1. for phenol: on the addition of 5 or 6 drops of hydrochloric acid and then 1 of nitric acid to the suspected fluid, a red color develops;
2. for strychnine: fluid is extracted with ether, which is then evaporated by means of "drop-by-drop" pipetting into a warmed porcelain dish or crucible; the residue is treated with drops of manganese dioxide and dilute sulfuric acid; a red-blue or violet color develops if strychnine is present.
3. a test for radial or ulnar patency; either the radial or ulnar artery is digitally compressed by the examiner after blood has been forced out of the hand by clenching it into a fist; failure of the blood to diffuse into the hand when opened indicates that the noncompressed artery is occluded.
Allen testTwo obsolete tests in clinical chemistry delineated by AH Allen (1846–1904) for detecting the presence of phenol and strychnine.
Al·len test(al'ĕn test)
A measurement of radial or ulnar patency; either the radial or ulnar artery is digitally compressed by the examiner after blood has been forced out of the hand by clenching it into a fist; failure of the blood to diffuse into the hand when opened indicates that the artery not compressed is occluded.
1. A bedside test used to evaluate the patency of the arteries of the hand before arterial puncture. The patient elevates the hand and repeatedly makes a fist while the examiner places digital occlusive pressure over the radial and ulnar arteries at the wrist. The hand will lose its normal pink color. Digital pressure is released from one artery (usually the ulnar), while the other (i.e., the radial) remains compressed. If there is normal blood flow through the unobstructed artery, color should return to the hand within 10 sec. The return of color indicates that the hand has a good collateral supply of blood and that arterial puncture of the compressed artery can be safely performed.
2. A procedure to identify the presence of thoracic outlet compression syndrome caused by tightness of the pectoralis minor muscle. With the patient seated, the examiner abducts the involved shoulder to 90° and flexes the elbow to 90°. While palpating the radial pulse, the examiner externally rotates the humerus while the patient actively rotates the head to the opposite side. A diminished or absent radial pulse is indicative of the pectoralis minor muscle's compressing the neurovascular bundle. This procedure often produces false-positive results.See: illustration; thoracic outlet compression syndrome.
Allen,Alfred Henry, U.S. chemist, 1846-1904.
Allen test - a test for phenol.
Allen,Edgar Van Nuys, U.S. physician, 1900-1961.
Allen test - a test for radial or ulnar patency.