Is the Allen test reliable enough?

Radial artery, Coronary artery bypass grafting, Ultrasonography, Allen test

I read with interest the article titled ‘Is the Allen test reliable enough?’‘ The authors enrolled in this study 145 patients who underwent [1] the Allen test, Doppler ultrasonography and digital plethysmography. They conclude that the Allen test is a good and valid screening test for the circulation of the hand.

In patients undergoing coronary artery bypass grafting surgery using radial artery grafts, is Allen’s test, modified Allen’s test, pulse oximetry, plethysmography, Doppler ultrasonography or magnetic resonance imaging the best method of assessing ulnar artery or collateral flow [2–4]?

Traditionally, the modified Allen’s test has been used to evaluate the patency of the ulnopalmar arches. However, the modified Allen’s test remains, at most, subjective especially when hand blushing is slow to occur. I stressed that a more objective test, the combination of modified Allen’s test and pulse oximetry, would also be more sensitive than the modified Allen’s test alone.

Barbeau et al. [3] studied 1010 patients to compare the modified Allen’s test with combined plethysmography and pulse oximetry test. They found that plethysmography and pulse oximetry were to be more sensitive than the modified Allen’s test, and only 1.5% of patients were not suitable candidates for the transradial approach.

In our clinic, I applied the modified Allen’s test [4,5], combined with the further modification as described by Johnson et al. An oxygen saturation monitor was attached to the index finger of the appropriate hand and a baseline measurement was taken. The maximum time to confirm a negative Allen’s test was considered to be 12 s. If the skin surface remained pale for longer than 12 s it indicated a positive Allen’s test.

Although the clinical modified Allen’s test was normal in all patients (n = 204), in three patients (1.5%) the preoperative combination of the modified Allen’s test and pulse oximetry was not normal. These patients were evaluated by Doppler ultrasonography, and contraindicate radial artery harvesting. We did not harvest the radial artery in these patients; in the remaining 201 patients (98.5%) the radial artery was harvested. We did not observe any case of postoperative forearm or hand ischemia.

In conclusion, combination of modified Allen’s test and pulse oximetry is a non-invasive, inexpensive and mobile procedure, which can easily be performed to evaluate the arterial supply of the hand. A negative combination of modified Allen’s test and pulse oximetry safely selects patients for radial artery harvest in the majority of patients. Doppler ultrasonography predicts safe radial artery harvest in the patients with a positive combination of modified Allen’s test and pulse oximetry.

© European Association for Cardio-Thoracic Surgery 2008