Is the Allen Test Necessary Before Transradial Artery Catheterization?

Authors: Bertrand OF et al., J Am Coll Cardiol 2014 May 13; 63:1842

No, according to a prospective study in which postprocedural concentration of thumb capillary lactate was used as the primary endpoint.

To address ongoing controversy about whether Allen test results predict ischemic complications of transradial artery (TRA) catheterization, investigators conducted a prospective study in 203 patients with normal (83), intermediate (60), or abnormal (60) Allen test results before TRA procedures. All patients also underwent preprocedure plethysmography and pulse oximetry (Barbeau test); ulnar contrast angiography frame count for collateral assessment during catheterization; and thumb capillary lactate assessment and handgrip-strength testing immediately after catheterization, at 30 days, and at 1 year.

The primary endpoint — postprocedural concentration of thumb capillary lactate — did not differ among the groups either immediately after the procedure or at follow-up assessments, despite an increase in all three groups immediately before catheter removal. Patient discomfort peaked and handgrip strength reached a nadir during radial occlusion, but each of these endpoints was similar among all three groups during and after catheterization. Asymptomatic absence of radial pulse at day 1 was observed in five participants, only one of whom had had an abnormal Allen test; spontaneous recanalization occurred in two of the five patients at 30 days. In both groups with non-normal Allan tests, collateral circulation (as measured by the Barbeau test) improved after TRA catheterization.

Comment

These findings suggest that an abnormal Allen test does not predict worse vascular outcomes for patients undergoing TRA catheterization. The authors propose that preexisting collateral vessels may be recruited during radial artery occlusion. Unlike previous investigations, this one showed no evidence of a greater increase in thumb capillary lactate concentration among patients with an abnormal Allen test. As noted in an accompanying editorial, the data from this careful mechanistic study suggest that results of both the Allen and Barbeau tests are unreliable predictors of distal ischemia after TRA catheterization, and that abnormal findings on these tests should not justify denial of radial access.