[Reliability and validity of the modified Allen test: a systematic review and metanalysis].

The objective was to evaluate the reliability and validity of the modified Allen test in screening for collateral circulation deficits in the palm and for predicting distal hand ischemia. We performed a systematic review of the literature indexed in 6 databases. We developed a search strategy to locate studies comparing the Allen test to Doppler ultrasound to detect circulation deficits in the hand, studies assessing the incidence of ischemic events on arterial puncture after an abnormal Allen test result, and studies of Allen test interobserver agreement. Fourteen articles met the inclusion criteria. Nine assessed the validity of the test as a screening tool for detecting collateral circulation deficits. From data published in 3 studies that had followed comparable designs we calculated a sensitivity of 77% and specificity of 93% for the Allen test. Four studies that assessed the ability of the test to predict ischemia did not predict any ischemic hand events following arterial puncture in patients with abnormal Allen test results. A single study assessing the test's reliability reported an interobserver agreement rate of 71.5%. This systematic review and metanalysis allows to conclude that the Allen test does not have sufficient diagnostic validity to serve as a screening tool for collateral circulation deficits in the hand. Nor is it a good predictor of hand ischemia after arterial puncture. Moreover, its reliability is limited. There is insufficient evidence to support its systematic use before arterial puncture.