Peta Ellen Tehan

Non-invasive vascular assessment in the foot with diabetes: sensitivity and specificity of the ankle brachial index, toe brachial index and continuous wave Doppler for detecting peripheral arterial disease

BACKGROUND & AIMS Non-invasive lower limb vascular assessment in people at risk of peripheral arterial disease (PAD) including those with diabetes is crucial. There is evidence that standard assessment techniques such as the ankle-brachial index (ABI) may be less effective in people with diabetes. However there is limited evidence for other frequently used tests including continuous wave Doppler (CWD), and the toe-brachial index (TBI). The aim of this study was to determine the sensitivity and specificity of, ABI, CWD and TBI in a population with, and without diabetes. METHODS Participants with and without diabetes who met current guidelines for vascular screening were recruited, and CWD waveforms, an ABI and a TBI were obtained from the right lower limb. Diagnostic accuracy was determined using colour duplex ultrasound (CFDU). Receiver operating characteristic curves were calculated. RESULTS 117 participants were recruited, seventy-two with diabetes and forty-five without diabetes. CWD had the highest sensitivity in people with diabetes (74%) and without (84%). CWD also had the highest specificity in people with diabetes (74%) and without (84%) compared to both TBI and ABI. In participants with diabetes, the ABI was a poor test, area under the curve: 0.58 (p=0.27). CONCLUSIONS CWD waveform is more likely to detect significant PAD compared to ABI and TBI in people with and without diabetes.

A systematic review of the sensitivity and specificity of the toe–brachial index for detecting peripheral artery disease:

The toe–brachial index (TBI) is used as an adjunct to the ankle–brachial index (ABI) for non-invasive lower limb vascular screening. With increasing evidence suggesting limitations of the ABI for diagnosis of vascular complications, particularly in specific populations including diabetes cohorts, the TBI is being used more widely. The aim of this review was to determine the sensitivity and specificity of the TBI for detecting peripheral artery disease (PAD) in populations at risk of this disease. A database search was conducted to identify current work relating to the sensitivity and specificity of toe–brachial indices up to July 2015. Only studies using valid diagnostic imaging as a reference standard were included. The QUADAS-2 tool was used to critically appraise included articles. Seven studies met the inclusion criteria. Sensitivity of the TBI for PAD was reported in all seven studies and ranged from 45% to 100%; specificity was reported by five studies only and ranged from 16% to 100%. In conclusion, this review suggests that the TBI has variable diagnostic accuracy for the presence of PAD in specific populations at risk of developing the disease. There was a notable lack of large-scale diagnostic accuracy studies determining the diagnostic accuracy of the TBI in detecting PAD in different at-risk cohorts. However, standardised normal values need to be established for the TBI to conclusively determine the diagnostic accuracy of this test.

Sensitivity and Specificity of the Toe-Brachial Index for Detecting Peripheral Arterial Disease Initial Findings

The toe‐brachial index (TBI) is an alternative to the ankle‐brachial index (ABI) in screening for peripheral arterial disease (PAD); however, there is limited evidence comparing their diagnostic accuracy. This study compared the diagnostic accuracy of the ABI and TBI in a population at risk of PAD.

Use of hand-held Doppler ultrasound examination by podiatrists: a reliability study

BackgroundHand held Doppler examination is a frequently used non-invasive vascular assessment utilised by podiatrists. Despite this, the reliability of hand-held Doppler has not been thoroughly investigated. Given the importance of Doppler in completing a vascular assessment of the lower limb, it is essential to determine the reliability of the interpretation of this testing method in practicing podiatrists.MethodsThis was a multi-centre inter and intra-rater reliability study. Four podiatrists (the raters) participated in this study, two public and two private practitioners. Three aspects of Doppler use were examined; (i) use of Doppler (i.e., technique and interpretation), (ii) interpretation of Doppler audio sounds, and (iii) interpretation of visual Doppler waveforms (i.e., tracings). Participants meeting current guidelines for vascular screening attended two testing sessions, 1 week apart at either the private practice (n = 32), or the public practice (n = 31). To assess use of Doppler, the raters evaluated the Doppler waveforms that they collected, rating them as mono-phasic or multi-phasic. To assess Doppler audio sounds and visual Doppler waveforms, raters were required to evaluate 30 audio recordings of Doppler sounds and 30 waveform tracings, respectively, that were previously recorded and chosen at random by the researchers. Cohen’s kappa (κ) statistics were used to calculate inter and intra-rater reliability using SPSS version 19.ResultsUse of Doppler demonstrated the lowest reliability for both pairs of clinicians (inter-rater reliability κ 0.20 to 0.24 and intra-rater reliability κ 0.27 to 0.42). The public podiatrists showed higher reliability in audio interpretation (inter-tester reliability κ 0.61, intra-tester reliability κ 1.00) compared to the private podiatrists (inter-tester reliability κ 0.31, intra-tester reliability κ 0.53). Evaluation of Doppler waveform tracings demonstrated highest reliability, with inter-rater reliability ranging from κ 0.77 to 0.90 and intra-rater reliability from κ 0.81 to 1.00.ConclusionsThere is a need for ongoing education for podiatrists using Doppler in clinical practice, as the reliability for the clinical use of the Doppler was low. This indicates that technique could be an issue. There is also a need to further evaluate if hand-held Doppler equipment, using the examinations that we evaluated, is suitable for use in the contexts examined in this study.

Toe brachial index measured by automated device compared to duplex ultrasonography for detecting peripheral arterial disease in older people

Introduction To investigate the diagnostic accuracy of an automated toe blood pressure device for detecting peripheral arterial disease in older people. Methods Ninety participants underwent toe and brachial blood pressure measurements and colour duplex ultrasonography of the right lower limb. Peripheral arterial disease was diagnosed if > 50% arterial obstruction was identified in any lower limb vessel using colour duplex ultrasonography. A receiver operating characteristic curve was analysed and the sensitivity and specificity of commonly used toe brachial index and toe blood pressure values were determined. Results The optimum toe brachial index threshold value for diagnosing peripheral arterial disease was 0.72 (sensitivity 76.2%, specificity 75%). The area under the curve was 0.829 (95% CI 0.743 to 0.915, p < 0.0001) suggesting fair diagnostic accuracy. A toe blood pressure of 70 mmHg was found to have excellent specificity (97.92%) for detecting PAD but poor sensitivity (42.86%). Conclusions The accuracy of automated toe blood pressure and TBI measurements was determined to be good when using colour duplex ultrasound as the reference standard for the non-invasive diagnosis of peripheral arterial disease. Results should be interpreted in the context of all clinical signs and symptoms.

A targeted screening method for non-invasive vascular assessment of the lower limb

BackgroundPodiatrists routinely perform non-invasive lower limb vascular assessment, however frequently cite time as a major barrier in performing regular assessment. The aim of this study was to develop an evidence-based vascular assessment method to guide podiatrists’ decision-making processes to aid in timely vascular assessment in at risk populations.MethodThe sample underwent brachial pressure measurement, ankle pressures, toe pressure and Doppler waveform with colour duplex ultrasound (CFDU) used as the reference standard. Both the targeted screening method and the American Heart Association (AHA) guideline for vascular screening were then applied to the data set and sensitivity and specificity of each method was calculated.ResultsOne hundred nineteen participants were included. Sensitivity of the targeted screening method (62%, 95% CI 47.17–75.35) was higher than the AHA method (49%, 95% CI 34.75–63.40), however, specificity of the AHA method (94%, 95% CI 85.62–98.37) was higher than the targeted screening method (85%, 95% CI 74.26–92.60). Diagnostic accuracy was similar with the AHA method yielding 74% diagnostic accuracy and the targeted screening method 73%.ConclusionThe targeted screening method and the broad international guideline demonstrated similar accuracy, however clinicians may save time using the targeted screening method. This study highlights the difficulties in obtaining accuracy in lower limb vascular assessment in general.

Diagnostic accuracy of the postexercise ankle–brachial index for detecting peripheral artery disease in suspected claudicants with and without diabetes:

The postexercise ankle–brachial index (ABI) is recommended in patients with normal resting ABI when peripheral artery disease (PAD) is suspected. The aims of this study were to determine the comparative diagnostic accuracy of the resting and postexercise ABI for detecting PAD, and, the effect of the presence of diabetes on these. Three methods of interpretation currently in use were also investigated: a reduction in postexercise ABI by >20% compared to resting ABI, an ABI value of ≤0.90 postexercise, or a reduction in systolic ankle pressure of >30 mmHg postexercise. This retrospective study used colour duplex ultrasound (CDU) as the reference standard. In 278 limbs (whole group), the resting ABI had an overall area under the curve (AUC) of 0.71, with the postexercise ABI yielding a similar diagnostic accuracy of AUC 0.72. In the non-diabetes group (n=171), the resting ABI had an overall AUC of 0.74 and the postexercise ABI had a similar AUC of 0.76. In the diabetes group (n=107), overall accuracy was reduced compared to the non-diabetes group, with the resting ABI having an overall AUC of 0.65 and the postexercise ABI yielding a similar accuracy with an AUC of 0.64. The overall diagnostic accuracy of the postexercise ABI for diagnosing PAD was not greatly improved compared to resting ABI. Given the lower overall diagnostic accuracy in the diabetes group, both the resting and the postexercise ABI results in diabetes populations should be interpreted with caution. There is a risk of undiagnosed disease if relying on these results alone to determine lower limb vascular status.

How sensitive and specific is continuous-wave Doppler for detecting peripheral arterial disease in people with and without diabetes? A cross-sectional study:

Background: Continuous-wave Doppler is frequently used for detecting peripheral arterial disease in patients with diabetes; however, there is limited evidence investigating diagnostic accuracy. This study aimed to determine sensitivity and specificity of continuous-wave Doppler for detecting peripheral arterial disease in populations with, and without, diabetes and to investigate the influence of disease severity on sensitivity of continuous-wave Doppler for detecting peripheral arterial disease. Results: Data from 396 participants were included. Using colour Duplex ultrasound as reference standard (N=66), printed continuous-wave Doppler waveform analysis sensitivity was 81.75% (95% confidence interval: 76.75 to 85.88) and specificity 89.34% (95% confidence interval: 82.62 to 93.67). Printed continuous-wave Doppler waveform analysis sensitivity for peripheral arterial disease was comparable to sensitivity calculated using angiography as the reference standard (81.67%; 95% confidence interval: 69.56 to 90.48). Sensitivity and specificity were unaffected by diabetes diagnosis (n = 176), sensitivity 82.76% (95% confidence interval: 74.86 to 88.55), and specificity 88.33% (95% confidence interval: 77.82 to 94.23). Conclusion: Continuous-wave Doppler is a fair assessment tool for peripheral arterial disease in a community-based sample with suspected peripheral arterial disease. Diagnostic accuracy of continuous-wave Doppler for peripheral arterial disease is unaffected by the presence of diabetes.