Allenstestet

Allenstestet, commonly referred to as the Allen test, is a simple bedside procedure used to assess arterial blood flow to the hand and the adequacy of collateral circulation between the radial and ulnar arteries. It is frequently performed before procedures that may compromise hand perfusion, such as radial artery cannulation or harvesting of the radial artery for grafts.

In the standard test, the examiner applies firm pressure over the radial and ulnar arteries at the wrist to occlude both vessels, causing the hand to blanch. The patient may repeatedly make a tight fist to aid drainage of venous blood. One artery is then released while the other remains compressed, and the clinician observes the return of color and perfusion to the hand. A prompt re-perfusion indicates adequate collateral flow from the released artery, whereas delayed or absent color return suggests insufficient collateral circulation and potential risk for ischemia if arterial access or harvesting is performed.

There are variations, including the modified Allen test, which uses Doppler ultrasound or pulse oximetry to confirm patency and timing of reperfusion. Modern assessment may combine the clinical test with imaging or vascular studies when indicated.

Limitations of the test include variability in technique and interpretation, dependence on patient cooperation, and factors such as edema, skin pigmentation, vasospasm, or peripheral vascular disease that can affect accuracy. The Allen test is a screening tool and does not replace imaging studies when precise assessment of arterial patency is required.