Abstract
BackgroundThe ankle-brachial index (ABI) is widely used for determining the presence and severity of peripheral arterial disease (PAD), and current guidelines suggest it should be used to monitor possible progression in affected individuals. It is therefore important that the technique demonstrates adequate reliability for repeated measurements. Existing studies suggest that the ABI is reliable in the general population however, there is a lack of evidence for the reliability of the ABI in people with diabetes. The aim of this study was to investigate the intra-tester reliability of the ABI in people with and without diabetes.MethodsEighty-five participants (40 with and 45 without diabetes) underwent ankle and brachial systolic blood pressure measurements by a single clinician during two testing sessions. Intraclass correlation coefficients (ICC), their 95% limits of agreement, standard error of measurement and minimal detectable change were determined.ResultsIntra-tester reliability of the ABI was found to be good (ICC: 0.80), however sub-group analysis of participants with and without diabetes found that ABI was slightly less reliable in people with diabetes (ICC: 0.78) than in those without (ICC: 0.82). The relatively large limits of agreement (− 0.16 to 0.16), standard error of measurement (0.03 overall, 0.04 for the diabetes group), and minimal detectable change (0.08 overall, 0.11 for the diabetes group) suggest that a large change in ABI is required for it to demonstrate a true change rather than the result of measurement variability. The minimal detectable change for the ABI was 0.08 overall, and 0.11 for the diabetes group.ConclusionsThe ABI demonstrated good reliability in all groups analysed. However, the wide limits of agreement and considerable standard error of measurement obtained support the use of multiple methods of vascular assessment for ongoing monitoring of lower limb vascular status.
Highlights
The ankle-brachial index (ABI) is widely used for determining the presence and severity of peripheral arterial disease (PAD), and current guidelines suggest it should be used to monitor possible progression in affected individuals
The intraclass correlation coefficient (ICC) values obtained suggest that the intra-tester reliability of the ABI is good, with values that are comparable to the findings of previous studies in mixed populations including those with risk factors for and/or suspected PAD [30,31,32]
Reliability relates to the consistency of the measurement as opposed to the accuracy, our results substantiate the need for multifaceted testing to be used as the variability of the measurement of the ABI likely further affects its effectiveness for identifying and monitoring PAD
Summary
The ankle-brachial index (ABI) is widely used for determining the presence and severity of peripheral arterial disease (PAD), and current guidelines suggest it should be used to monitor possible progression in affected individuals. Peripheral arterial disease (PAD) is estimated to affect up to 12% of the general population [1], and up to 14% of people with diabetes [2]. Due to the high risk of concurrent cardiovascular disease, and lower limb complications associated with PAD, The ankle brachial index (ABI) is typically calculated as the ratio of the highest of the dorsalis pedis and posterior tibial artery systolic pressure to the highest of the left and right brachial systolic pressures [7]. Current international guidelines recommend the ABI be used routinely to monitor for PAD in older people, those with a smoking history and in people with diabetes [8, 9]
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