An evaluation of the reliability and validity of capillary refill time test

Background: While capillary refill time test (CRTT) has been commonly used as a quick and convenient clinical vascular assessment of the lower limb, the validity of this test has not been established. Objectives: There were three aims to this study: the first was to evaluate the reliability of CRTT, the second to investigate the premise that CRTT represents skin perfusion, and thirdly to determine whether CRTT can detect lower limb vascular disease. Method: Intra- and inter-tester reliability was evaluated for five experienced physicians who used CRTT on 10 participants. Criterion validity for measurement of skin perfusion was investigated by comparison with laser Doppler flowmetry on 49 participants, and for this same group the usefulness of detecting those persons with peripheral arterial disease and a state of impaired healing was evaluated. Results: CRTT had reasonable intra-tester reliability (ICC = 0.72) but poorer inter-tester reliability (ICC range = 0.12-0.81). For measurement of skin perfusion, CRTT was predictive of only 38% of the variance in laser Doppler flowmetry measures (r² = 0.38, P < 0.001). Finally, CRTT was not able to discriminate between patients with and without peripheral arterial disease (z = -1.86, P = 0.062), nor could it discern between patients with and without impaired lower extremity healing (z = -0.21, P = 0.830). Laser Doppler flowmetry was also unable to predict the presence of peripheral arterial disease (t₉₆ = 0.27, P = 0.787) and impaired healing (t₉₆ = 1.95, P = 0.054). Conclusion: These results question the usefulness of capillary refill time test for assessment of vascular status in the lower limb.