During Allen's test, a positive result is indicated by ...

• A. Abnormal coloration with refill time >5 seconds
• B. Normal coloration within 1 second
• C. Rapid color return within 0.5 seconds
• D. No color change

Answer: (A)

Allen's test assesses how well the hand is supplied by collateral circulation through the palmar arches when one artery is temporarily blocked. The test is positive when, after releasing one artery, the color in the hand does not return promptly and the refill time is prolonged—typically taking more than about 5 seconds. This indicates the hand would rely on a compromised artery for perfusion, showing inadequate collateral flow.

If color returns quickly, within about 1 second or even 0.5 seconds, that means the collateral pathways are functioning well, which is a negative result. No color change would suggest a severe lack of perfusion, which is not the typical positive finding and could reflect an abnormal or improperly performed test or complete occlusion.