Diagnostic Accuracy of Point-of-care Tests Used to Detect Arterial Disease in Diabetes: TEsting for Arterial Disease in Diabetes (TrEAD) Study.

OBJECTIVE: We compared the diagnostic performance of a novel point-of-care duplex ultrasound test (podiatry ankle duplex scan; PAD-scan) against commonly used bedside tests for the detection of PAD in diabetes. BACKGROUND: PAD is a major risk factor for diabetic foot ulceration and amputation. Its diagnosis is fundamental though challenging. Although a variety of bedside tests are available, there is no agreement as to which is the most useful. PAD-scan may be advantageous over current tests as it allows for vessel visualization and more accurate arterial waveform assessment. However, its accuracy has not been previously evaluated. METHODS: From March to October 2019, we recruited 305 patients from 2 diabetic foot clinics. The diagnostic performance of ankle-brachial pressure index, toe-brachial pressure index, transcutaneous pressure of oxygen, pulse palpation, and ankle waveform assessment using PAD-scan and Doppler devices (audible and visual waveform assessment) were assessed. The reference test was a full lower limb duplex ultrasound. RESULTS: Based on the reference test, 202 (66.2%) patients had evidence of PAD. PAD-scan had a significantly higher sensitivity [95%, confidence interval (CI) 90%-97%) as compared to all other tests. Particularly low sensitivities were seen with pulse palpation (43%, CI 36%-50%) and transcutaneous pressure of oxygen (31%, CI 24%-38%). PAD-scan had a lower specificity (77%, CI 67%-84%) compared to toe-brachial pressure index (86%, CI 78%-93%; P < 0.001), but not statistically different when compared to all other tests. CONCLUSIONS: PAD-scan has superior diagnostic utility and is a valid first line investigation.

Study protocol for a comparative diagnostic accuracy study of bedside tests used to detect arterial disease in diabetes: TEsting for Arterial disease in Diabetes (TrEAD) study.

INTRODUCTION: In the UK, over 7000 amputations are performed each year because of diabetes. Up to 80% of these are preceded by a foot ulcer and could therefore be prevented with improvements in ulcer care. Peripheral arterial disease is an important risk factor for the development of diabetic foot ulceration. However, its diagnosis in diabetes is challenging due to the presence of neuropathy and arterial calcification. Commonly used bedside tests either have low sensitivities or little supporting evidence to justify their use. Duplex ultrasound (DUS) has good correlation to angiography findings but a full scan is difficult to learn and time consuming to perform. We have previously demonstrated that a focused DUS of the distal anterior and posterior tibial arteries at the ankle (podiatry ankle duplex scan (PAD-scan)) can be readily learnt by novices and performed rapidly and accurately. The primary aim of this study is to determine the diagnostic accuracy of the PAD-scan and other commonly used bedside tests in detecting arterial disease in diabetes. METHODS AND ANALYSIS: The study will include 305 patients presenting to diabetic foot clinics at two centres. Arterial assessment will be performed using the following index tests: the PAD-scan, pulse palpation, audible handheld Doppler, Ankle Brachial Pressure Index, Toe Brachial Pressure Index and transcutaneous pressure of oxygen. Patients will then undergo a full lower limb arterial DUS by a blinded vascular scientist as a reference test. ETHICS AND DISSEMINATION: Approval was gained from NRES Committee London (REC reference 17/LO/1447). Findings will be disseminated by various methods including international presentations and publication in a peer-reviewed journal. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov Registry (NCT04058626).