No Bedside Test Has Superior Diagnostic Accuracy for Peripheral Artery Disease

No individual bedside test or combination of bedside tests has demonstrated superior diagnostic accuracy for peripheral artery disease (PAD), according to systematic review findings published in Diabetes/Metabolism Research and Reviews.

Noninvasive PAD tests are important for early diagnosis and management of lower limb PAD, which reduces risks related to cardiovascular complications, nonhealing of wounds, development of diabetic foot ulceration (DFU), and amputation. Researchers therefore conducted a systematic review to evaluate the diagnostic accuracy of clinical examination and noninvasive bedside tests for identifying PAD, compared with an imaging reference test. They also assessed the reliability of various noninvasive bedside tests in adults with diabetes.

The reviewers searched the Medline and Embase databases from 1980 through November 2022 for relevant studies. PAD was defined as any obstructive atherosclerotic disease of the arteries from the distal aorta to the foot. Included studies  evaluated clinical examination, a pedal pulse palpation, or a noninvasive bedside test, comparing these modalities with a standard reference test. Primary study endpoints were positive likelihood ratio (PLR; ≥10 indicates good performance) and negative likelihood ratio (NLR; ≤0.1 indicates good performance).

A total of 40 studies met reviewers’ criteria for assessing diagnostic accuracy and 7 met criteria for assessing reliability. A majority of the studies (38) evaluated the diagnostic accuracy of the ankle-brachial index (ABI); toe-brachial index (TBI), toe pressure, transcutaneous oxygen pressure, and pulse palpation were also assessed.

Regarding clinical examination, 2 studies in a diabetic population without DFU found that palpable pulses did not rule out the presence of PAD (NLR 0.25-0.43); when a foot pulse was absent or weak, there was a small increase in disease risk (PLR 1.84-2.46).

Regarding ABI, among patients with DFU, PLRs ranged from 1.69 to 2.32 and NLRs ranged from 0.52 to 0.75. For studies with limited DFU, PLRs ranged from 2.1 to 19.9 and NLRs ranged from 0.29 to 0.84.

TBI diagnostic accuracy was evaluated in 8 studies. PLRs ranged from 1.62 to 10 or more, and NLRs ranged from 0 to 0.70; diagnostic thresholds for the index test were highly variable (ranging from ≤0.38 to ≤0.75).

With respect to continuous wave Doppler, PLR and NLR scores demonstrated a moderate to high predictive ability to identify PAD (PLRs ranged from 2.93 to ≥10; NLRs ranged from 0 to 0.35).

In the analysis of reliability, researchers found that ABI, toe pressure, and TBI had good inter- and intra-rater reliability, but with large margins of error. The intra-rater reliability of ABI was also reported in 1 study; the intraclass correlation coefficient (ICC) was 0.82 (95% CI, 0.70-0.90). The intra-rater reliability of TBI was found to be moderate to good; ICCs ranged from 0.51 to 0.77. For toe pressure, the intra-rater reliability was found to be good to excellent; ICCs ranged from 0.88 to 0.93. Inter‐rater reliability was poor for pulse palpation and moderate for transcutaneous oxygen pressure.

Overall, results indicated that ABI thresholds of less than 0.9 or greater than 1.3, TBI scores of less than 0.70, and absent or monophasic pedal Doppler waveforms can be used to identify the presence or absence of PAD.

Limitations of this study include the lack of meta-analysis, which restricts the generalizability of the results.

The authors concluded, “no single bedside test or a combination of bedside tests has been shown to have superior diagnostic accuracy for PAD.” They added, “Available data suggest that reliability is acceptable for several tests (eg, ABI, TBI and toe pressure), but these tests are affected by measurement error and change in test results requires careful interpretation.”