Background: Allen's test is widely used to assess the ulnar collateral blood supply of the hand before radial artery harvest for coronary bypass surgery. This study was performed to determine the optimum cut-off point for a positive Allen's test and the clinical reliability of Allen's test in this role.
Methods: Patients undergoing coronary artery bypass surgery were examined by independent observers using both Allen's test and a Doppler ultrasound test of the ulnar collateral circulation.
Results: We examined 93 hands in 47 patients; mean age was 63.6 years. Receiver operating characteristic analysis found that at a conventional cut-off of 6 seconds on Allen's test had a sensitivity of 54.5%, specificity of 91.7%, and diagnostic accuracy of 78.5%. At a cut-off of 5 seconds diagnostic accuracy was maximal (79.6%), with sensitivity of 75.8% and specificity of 81.7%; 100% sensitivity occurred at a cut-off of 3 seconds, with specificity of 27% and diagnostic accuracy of 52%.
Conclusions: At no cut-off point does Allen's test perform satisfactorily as a discriminatory test. It should be replaced by more objective tests, such as Doppler ultrasound.