Peripheral arterial disease screening and diagnostic practice: A scoping review

Abstract

Early reliable, valid screening, diagnosis, and treatment improve peripheral arterial disease outcomes, yet screening and diagnostic practices vary across settings and specialties. A scoping literature review described reliability and validity of peripheral ischaemia diagnosis or screening tools. Clinical studies in the PUBMED database January 1, 1970, to August 13, 2018, were reviewed summarising ranges of reliability and validity of peripheral ischaemia diagnostic and screening tools for patients with non‐neuropathic lower leg ischaemia. Peripheral ischaemia screening and diagnostic practices varied in parameters measured such as timing, frequency, setting, ordering clinicians, degree of invasiveness, costs, definitions, and cut‐off points informing clinical and referral decisions. Traditional ankle/brachial systolic blood pressure index <0.9 was a reliable, valid lower leg ischaemia screening test to trigger specialist referral for detailed diagnosis. For patients with advanced peripheral ischaemia or calcified arteries, toe‐brachial index, claudication, or invasive angiographic imaging techniques that can have complications were reliable, valid screening, and diagnostic tools to inform management decisions. Ankle/brachial index testing is sufficiently reliable and valid for use during routine examinations to improve timing and consistency of peripheral ischaemia screening, triggering prompt specialist referral for more reliable, accurate Doppler, or other diagnosis to inform treatment decisions.

Abbreviations

6MWD

6‐minute walking distance

ABI

ankle/brachial index or resting systolic blood pressure ratio

ALU

arterial leg ulcer

CLI

critical limb ischaemia

CTA

computed tomographic angiography

DSA

digital subtraction angiography

DUS

Doppler ultrasound

HbA₁C

fasting haemoglobin A₁C

MLU

mixed arterial leg ulcer with other causes such as venous insufficiency or diabetes mellitus

MRA

magnetic resonance angiography

MWD

maximum walking distance

NIRS

near infrared spectroscopy

NPV

negative predictive value

PAD

peripheral arterial disease

PCP

primary care physician

PPV

positive predictive value

PVR

pulse volume recording

PWV

pulse wave velocity

TBI

toe/brachial ratio of resting systolic blood pressure

TcPO₂

transcutaneous partial pressure of oxygen

1. INTRODUCTION

Fundamental shifts in lifestyle, diet, and exercise as industrialisation emerged generated a wave of peripheral arterial disease (PAD).1 Those with leg ulcers complicated by PAD face a prognosis of death and disability more likely than most dreaded cancers,2 yet PAD remains underdiagnosed and outcomes need improvement.3, 4 Consistently applied disease management programmes improved wound infection, hypertension, and oncology outcomes and may similarly help patients with PAD.

Implementing a PAD management approach (Figure 1) begins with reliable, consistent screening at the earliest point of primary care, usually based on physical symptoms of PAD for those at least 50 years of age such as an ankle/brachial systolic blood pressure ratio (ABI) <0.95 or absence of pedal pulse, cool limb,6 walking difficulties, or pallor on elevation.6, 7 Patients with such symptoms should receive immediate, appropriate referral(s) for accurate, sensitive, and specific differential diagnosis to facilitate effective treatments administered by trained professionals.

Figure 1.

Disease management plans for improving outcomes for individuals with PAD require consistent, effective interventions, and feedback to all involved patients and care providers at every step. PAD, peripheral arterial disease

For patients whose PAD has progressed to tissue loss, after ruling out non‐vascular causes, current practice for diagnosing an ischaemic leg ulcer is to measure the severity of ischaemia using a resting ABI.7 Vascular pathology is ideally confirmed by Doppler ultrasound (DUS) or other non‐invasive means of visualising arterial blood flow obstruction.

Differential diagnosis of leg ulcers complicated by PAD is typically confirmed by an ABI value <0.9.8 Chronic leg ulcers of mixed arteriovenous aetiology (mixed leg ulcers or MLUs) typically have ABI values ranging from 0.51 to 0.85.9 Arterial leg ulcers (ALUs) result from arterial occlusion without complicating conditions such as diabetes mellitus or venous insufficiency. These are typically diagnosed if pedal or tibial pulses are diminished, and then confirmed by DUS or invasive angiographic imaging. ABI values <0.9 predict likely ALU or MLU healing with rigorous conservative treatment to address all ulcer causes and aggressive wound care if local transcutaneous partial pressure of oxygen (TcPO₂) is >30 mmHg.10 ABI < 0.7 is the Trans‐Atlantic Intersociety Consensus definition of ischaemic limbs with an uncomplicated full‐thickness foot or leg ulcer existing over 6 weeks before study.6 If ankle pulses are obscured by vascular calcification, toe/brachial systolic blood pressure ratio (TBI) may serve as a reliable substitute for ABI in those with or without diabetes mellitus.11 Diagnostic blood tests for high LDL cholesterol or triglyceride levels may identify the causes of atherosclerosis to be addressed along with fasting haemoglobin A₁C (HbA₁C) to monitor glycaemic control.

Trained professionals ideally engage patients and all involved caregivers in implementing effective interventions in accessible settings, informing all those involved in patient and ulcer management of healing and PAD progression based on validated outcome surveillance.12

To optimise PAD management outcomes, using time and energy wisely, all specialties involved in each phase of the PAD management cycle (Figure 1) would ideally work in harmony without duplicating or undoing each other's work, communicating consistently, and applying the most reliable, valid PAD screening and diagnostic tools at hand. Objective assessment of the state‐of‐the‐art PAD screening and diagnostic practices could lay the foundation for improved timing and consistency of PAD screening, risk factor management, and diagnosis to inform clinical decisions, powering the disease management cycle to quell the deadly PAD pandemic.

2. PURPOSE

To support multidisciplinary team communications and functions in managing PAD, the authors conducted a scoping review of literature summarising evidence of reliability or validity of PAD screening or diagnostic tools in order to identify tools useful for health care professionals of all specialties in all settings to manage and properly refer affected patients.

3. METHODS

The authors conducted systematic searches of evidence in the National Library of Medicine PUBMED reference database from January 1, 1970, to August 13, 2018, supporting reliability or validity of PAD screening or diagnostic tools. Original and derivative references were included from systematic searches addressing MeSH terms for [“ischemia” OR “peripheral arterial disease”] AND [“diagnosis” OR “screening”] combined with [“clinical trial” OR “review”]. Abstract text and accessible full text or relevant derivative unique references were searched for adjectives or nouns reflecting screening or diagnostic “validity” or “reliability” as defined in Table 1.13, 14 Preclinical studies or clinical trials on patients with non‐ischaemic conditions were excluded to assure relevance of screening or diagnostic validity to patients with PAD.

Table 1.

Definitions used for PAD test reliability, screening validity measured as PPV and NPV, and diagnostic test validity measured as sensitivity and specificity

Quality measure	First common measure	Second common measure	Clinical example of the measure and accuracy of measurement
Reliability (High > 0.80) (Low < 0.70)	Test‐retest (TR) accurately repeatable by 1 rater (intra‐rater) at point‐of‐care screening and again at later PAD confirmation using the diagnostic test	Inter‐rater (IR) accurately repeatable by >1 rater in the same settings as described for TR reliability	Interclass correlation (ICC = r 2), Cohen's kappa (κ), or % agreement of repeated observations on the same patient within days. It reflects consistency of screening or diagnosis by the same or different observers supporting consistent care
Screening validity (High > 80%) (Low < 70%)	PPV: Point‐of‐care observer unaware of true PAD status reports PAD presence or increased severity	NPV: Point‐of‐care observer unaware of true PAD status reports PAD absence or decreased severity	For patients entering practice or enrolling in a study, high PPV means few false‐positive PAD reports; high NPV means few false negatives. Screening accuracy is % of all screened who were correctly screened as having or free of true PAD
Diagnostic validity (High > 80%) (Low < 70%)	Sensitivity: Diagnostic test performed by a trained specialist in controlled setting identifies the presence of true PAD accurately	Specificity: Diagnostic test performed by a trained specialist in controlled setting identifies the absence of true PAD accurately	Sensitivity is the % correctly diagnosed with PAD. Specificity is the % correctly diagnosed without PAD. Diagnostic accuracy is the % of all patients correctly diagnosed as having true PAD or not having true PAD

Notes: Validity of each test was determined comparing test results to an objective standard measure of “true” PAD severity such as Doppler ultrasonography or arteriography diagnosed by trained specialist(s).

Abbreviations: NPV, negative predictive value; PAD, peripheral arterial disease; PPV, positive predictive value.

Facts were verified by reading full‐text articles or contacting authors or websites identified using the Internet‐based Google Scholar search engine. Reviews and secondary sources were used when the primary source was inaccessible.

Qualifying studies with non‐redundant evidence were tabulated in a Microsoft Office‐based EXCEL file listing the studies and numbers of patients in each study supporting PAD diagnosis. It was inappropriate to average data derived from non‐homogeneous patient samples and settings, gathered by varying clinical specialties, so descriptive ranges of maximum and minimum reliability and validity were displayed. A gross estimate of the combined reliability and validity of each PAD screening or diagnostic tool was its graphically represented ranges of reliability, positive and negative predictive values, and sensitivity and specificity values.

Resulting evidence was reviewed in the context of clinical practice for the PAD management cycle (Figure 1) using the most valid, reliable parameters for PAD screening during routine history and physical examination to trigger specialist referral for valid, reliable diagnosis and inform subsequent PAD management.

4. RESULTS

The literature search returned 434 references plus two derivative references described in the PRISMA15 flow chart in Figure 2. Of these, 62 studies on 10–614 patients reported PAD screening or diagnostic parameters' reliability or validity during use in clinical practice.

Figure 2.

PRISMA flow diagram of literature searches on screening or diagnosis of PAD. PAD, peripheral arterial disease

4.1. State‐of‐the‐art PAD screening and diagnosis

PAD screening and diagnosis timing and reporting practices varied across specialties or settings and with severity of lower leg ischaemia as illustrated in Table 2.16, 17, 18 Inconsistent reporting left evidence gaps for comparing the outcomes. Non‐homogeneous samples made it inappropriate to average objective evidence supporting reliability and validity of the screening or diagnostic tools, so Figure 3 displayed estimates of each parameter's reliability and validity as a screening or diagnostic tool as the maximum and minimum reported values in studies supporting its reliability and screening or diagnostic validity. Tests requiring specialist referral are indicated by the arrow and box in Figure 3.

Table 2.

Variations in PAD clinical studies' reported screening or diagnostic parameters and outcomes made it difficult to compare the trends in those with PAD managed conservatively

Study parameters	Marston et al15	Chiriano et al16	Abu Dabrh et al17
PAD diagnostic or screening criteria used for study inclusion	Patients with an uncomplicated leg or foot ulcer and ABI < 0.7, meeting Trans‐Atlantic Intersociety Consensus definition of ischaemic limbs (N = 142) who were not candidates for revascularisation	Among 178 US veterans with no pedal pulse and ABI < 0.9 referred to a US university medical centre assigned to standardised care for a non‐healing leg or foot ulcer, 49 were managed conservatively	Analysis of 13 controlled studies of 1527 patients with severe ischaemia or CLI including tissue damage was managed without revascularisation
PAD outcomes reported	25% healed by 6 months 52% healed by 1 year 28% toe amputations or other foot sparing surgery 23% major amputations by 1 year	67% healed in a mean of 4.5 months; 1 had a major amputation; 75% were not revascularised; 25% were later revascularised with no increased risk of mortality or amputation	22% died in 1 year 22% major amputation 35% wound worsened

Abbreviations: ABI, ankle/brachial index; CLI, critical limb ischaemia; PAD, peripheral arterial disease.

Figure 3.

Highest and lowest value ranges of reliability and screening or diagnostic validity parameters are displayed as stacked bars for common PAD measures. Each PAD measure category is followed by the number of supporting studies (patients). A maximum bar height of 6.0 would represent perfect reliability and screening and diagnostic validity for the indicated parameter. Low bar height represents limited evidence of reliability or validity for the PAD measure. PAD measures in box required referral by a trained specialist to achieve the reliability and validity ranges displayed. PAD, peripheral arterial disease

Tests with the strongest overall reliability and screening or diagnostic validity were ABI measured using DUS ABI19; laser Doppler flow20; or invasive angiography measured using DUS, magnetic resonance angiography (MRA), or near infrared spectroscopy (NIRS). Haemodynamic, pulse volume recording (PVR), TcPO₂, and maximum walking distance (MWD) measures were also highly reliable and valid. The most commonly used standard against the tests that were validated was invasive digital subtraction angiography (DSA), which has a 1 to 3% incidence of neurologic, haemorrhage, or arterial complications, including seizures, arterial obstruction, and pseudo–aneurysms; vessel perforation; or extra luminal contrast material.21 Less invasive diagnostic techniques are preferred in order to avoid these complications.

The literature searches confirmed that DUS‐measured ABI <0.922, 23, 24 is a reliable, valid non‐invasive test to detect PAD during routine history and physical examinations in primary care settings,25 though the extra time and effort of using DUS may not be practical in most primary care settings. Non‐DUS ABI was less reliable than DUS ABI and lacked evidence of screening PPV or NPV in this literature search, but may serve as a preliminary screening tool as it had high diagnostic specificity in ruling out PAD in a Scandinavian study on 108 patients with high cholesterol.26

ABI measures were also sufficiently valid and reliable to use as a criterion for PAD severity during clinical study enrolment or follow‐up surveillance. ABI values <0.5 reflected more severe PAD with less likely healing outcomes.27 Colour or ultrasound Doppler systolic pressure readings were reliable28 and ideally performed consistently on the same arterial segment.29 Systolic pressure readings were more reliable using DUS as compared to stethoscope30, 31 or for ankle as compared to toe pressures for those with non‐calcified vasculature.18 When ABI ratios exceeded 1.3 reflecting arterial calcification,32 toe/brachial index systolic pressure <0.9 was a reliable screen for PAD.33

DUS, colour‐enhanced MRA, and NIRS were valid, reliable screening,34, 35 and diagnostic36, 37 techniques for advanced PAD, informing revascularisation decisions and localising sites of arterial occlusion or ruling out the presence of TASC II C or D infrainguinal arterial lesions requiring intervention and differentiating embolic from thrombotic acute limb ischaemia.38 However, DUS sensitivity in detecting true PAD confirmed by invasive intra‐arterial DSA varied from proximal to distal arterial segments39 and with severity of stenosis measured as percent reduction below normal arterial diameter levels, yielding significantly different diagnostic levels of PAD severity compared with invasive DSA.40, 41 Also DUS produced more false‐positive PAD diagnoses compared with simple visual evaluation of those with non‐significant arterial stenosis.42 To avoid false‐negative PAD diagnoses due to high DUS ankle or toe systolic pressures caused by thickened or stiff arterial walls, simultaneous low Doppler blood flow velocity results identified more patients with angiographically confirmed PAD as compared to DUS alone.43 Angiography is an invasive diagnostic procedure with complications, including vessel damage, bleeding, thrombosis, and infection.

Skin perfusion pressure exceeding 40 mmHg combined with toe blood pressure at least 30 mmHg was a valid predictor of ischaemic leg ulcer healing in patients with or without diabetes mellitus.44 Toe or ankle systolic blood pressure measures had high reliability after 5 or 10 minutes supine patient rest45, 46 and were unbiased by clinical cues.47

TcPO₂ measured in three leg sites following exercise had 100% diagnostic sensitivity and specificity in 138 patients with angiogram‐confirmed PAD, but sensitivity dropped to 77% for resting leg TcPO₂.48 All 34 claudicants reduced TcPO₂ after exercise in one Japanese study, which also used TcPO₂ < 30 mmHg as a non‐invasive standard circulation outcome measure.49 TcPO₂ also served as a reliable measure of amputation stump microcirculation confirmed by NIRS.50

Haemodynamic measures of PVR, toe systolic pressures, arterial blood flow rates, and tissue oxygenation of haemoglobin measured using digital pulse oximetry51, 52 or DUS53 or standard or dynamic computed tomographic angiography (CTA)54 had good reliability and diagnostic specificity, ruling out false‐negative PAD diagnoses of stenosis or occluded arteries verified by DSA. Pulse wave velocity (PWV) measurements and ankle divided by brachial PWV were reliable haemodynamic measures, but screening and diagnostic validity were not reported.55, 56 Leg muscle oxygen perfusion following femoral arterial occlusion to simulate exercise had good diagnostic validity.57 Brachial and popliteal artery diameters or various lower limb perfusion parameters also served as valid study outcomes, correlated with DUS or venous occlusion plethysmography or NIRS.58, 59 Non‐invasive NIRS of the dorsal foot after 10 toe‐flexes also had strong reliability and diagnostic validity accurately reflecting PAD‐related blood‐flow restriction, claudication pain, and ABI, but not in individuals with PAD complicated by diabetes mellitus.60, 61 Two variations on blood volume recording that can be very valuable are toe pressures and PVR.

Simple or contrast‐enhanced MRA had 88.9% accuracy for diagnosing occluded or stenosed pelvis or femoral arteries,62, 63 distal arteries64 or collaterals,65, 66 and predicted endoscopic revascularisation outcomes better than PAD determined by DSA.67 MRA improved decision support for performing balloon angioplasty68 or vascular surgery69, 70 on hospitalised patients with PAD requiring revascularisation though resolution was limited in calf arteries.59 Avoiding adverse reactions to contrast dies, non‐contrast MRA was a reliable, valid screening, and diagnostic option with clear images in popliteal and lower leg arteries.71, 72, 73

Several measures contributed to reliability and validity of haemodynamic outcomes. Peak arterial blood velocity was reliable and valid as an outcome measure for clinical study effects of thermotherapy74 or prostacyclin plus peroneal nerve stimulation75 on patients with PAD. Collateral artery counts and capillary perfusion measured by MRA were reportedly reliable outcome measures in clinical studies,76 reflecting total vessel counts and lumen volumes.77

For planned lower extremity bypass, DUS or CTA provided reliable information to determine if the greater saphenous vein diameter was at least 3 mm, adequate for use as a conduit,78 and had strong predictive validity supporting decisions for surgical or conservative management of patients with intermittent claudication.79 Transcatheter and multidetector CTA imaging were also highly sensitive and specific for detecting more than 50% stenosis on a per‐patient or per‐arterial segment basis,80, 81 but rating angiographic parameters was only moderately reliable for arterial lesions below the knee.82, 83, 84

PAD with intermittent claudication reportedly affected 12% of the US population, decreasing functional status and quality of life,85 yet these measures were rarely included in PAD studies. MWD at standardised km/h and inclination,86, 87 and GPS‐measured walking metrics were sufficiently reliable88, 89, 90 and valid to use for clinical screening of PAD claudication,89, 91, 92, 93, 94 even if complicated by diabetes mellitus.95, 96 MWD and foot skin temperatures were sufficiently reliable and valid to measure significant effects over time and between clinical trial groups randomised to receive 4 or 12 weeks of calf muscle neuromuscular stimulation.89, 91 Patient walking impairment questionnaires and distance to initial claudication were less reliable.97 Muscle weakness98 and total steps taken in the 6‐minute walk (6 MW) test were strongly correlated with ABI in patients with an average ABI of 0.61.99 A study of 22 participants with PAD and ABI values ranging from 0.28 to 0.82 reported significant correlations between ABI and a variety of lower limb muscle strength and balance measures including maximum and pain‐free walking distance in response to 3 months of structured exercise training programmes following Doppler‐confirmed revascularisation.100 Accelerometer and pedometer activity measures were reliable in PAD patients, but remain to be validated.101

Rutherford and/or Fontaine scores traditionally used to describe symptoms and functional limitations of patients with PAD were often used as clinical study enrolment or outcome criteria.102, 103 The literature search returned no reports of reliability, screening, or diagnostic validity for either of these descriptive scores, but they were strongly correlated with colour DUS, ABI, oedema, or other measures of arterial or venous function.104, 105

Scant diagnostic or screening evidence was found supporting reliability or validity of patient history of intermittent claudication, walking questionnaires, absence of hair on the ischaemic leg, pallor, and invasive angiograms.

5. DISCUSSION

Despite growing realisation that PAD management requires a harmonised multidisciplinary approach addressing all PAD causes relevant to each patient, PAD screening and diagnosis remain sporadic and fragmented across specialties and settings. This scoping review of the last 48 years of clinical research on PAD diagnosis and screening revealed good reliability and validity of DUS‐measured ABI <0.9 and fair reliability of non‐DUS ABI <0.9 before PAD progressed to arterial calcification. This suggests that ABI is sufficiently reliable and valid for use by primary care providers to screen and refer patients early for more consistent accurate diagnosis by specialists to inform conservative and invasive decisions to stop PAD progression before ensuing tissue loss, amputation, or mortality.

5.1. Implications for practice

Delaying PAD testing and diagnosis until its complications become severe contributes to its clinical, economic, and patient burdens. Research has focused on surgical and endovascular techniques to improve outcomes for patients with PAD.106 The fact that PAD is emerging faster in more developed countries1 suggests the merit of proactive diet and lifestyle interventions such as physical therapy, structured exercise, nicotine cessation, and control of dyslipidaemia to slow a patient's PAD progression before atherosclerosis is widely established.107

This becomes feasible only if primary care physicians (PCPs) use consistent reliable, valid screening, and diagnostic tools to identify early or established PAD at the earliest point of care during thorough history and clinical examinations using non‐invasive studies (Figure 1). Using ABI <0.9 as an evidence‐based non‐invasive trigger for specialist referral for more accurate diagnosis of PAD can encourage multidisciplinary communication and facilitate earlier diagnosis and treatment of individuals with PAD without requiring PCPs to invest in more expensive diagnostic instruments.

Longer‐term PAD management to optimise the quality of life and limb survival would continue all relevant interventions, using rigorous surveillance across the settings of validated outcomes related to PAD progression, including ALU, MLU and CLI, ischaemic pain, claudication, increased infection risk, and likelihood of amputation.108

Undiagnosed PAD patients make more visits to their PCP offices and wound centres with more out‐of‐pocket expense, more frequent hospitalisations, and risk losing health insurance if their employment is threatened.109 Adding simple reliable, valid screening, and surveillance tools to routine physical exams could reduce these burdens of PAD, while improving reporting of PAD epidemiology and outcomes.

The screening and diagnostic tools identified as satisfactory in this review are combined with current checklists110, 111 and proposed quality measures112 in a proposed PAD checklist (Figure 4) designed to harmonise early inter‐specialty communication of all engaged in PAD screening, referral, and management.

Figure 4.

Proposed checklist to harmonise early PAD screening and diagnosis by activating a multidisciplinary team approach in PAD disease management. PAD, peripheral arterial disease

The reliability and validity of PAD screening and diagnostic techniques establishes that the field is ready to follow the example of surveillance programmes for infection, hypertension, and oncology by developing an effective standardised PAD screening, diagnosis, and surveillance initiative across specialties and settings.

5.2. Implications for research

Reliability of ABI varied with operator experience, measurement techniques, and cut‐off points.113 More clarity is needed to inform decisions regarding levels of therapeutic compression for those with PAD,114 decisions supporting conservative care or revascularisation,10 or amputation of patients with critical limb ischaemia.17

PAD diagnosis, screening, and surveillance help patients only if implemented consistently in outpatient settings where most PAD is identified.115 PCP electronic medical records offer an efficient option to facilitate such communications among patients, PCPs, and vascular or other specialists. Electronic medical records or a checklist (Figure 4) could prompt community care nursing agencies or physicians conducting routine physical exams, office visits, or community screening events to measure ABI for all patients with one or more PAD risk factors, triggering diagnostic referral to a vascular specialist if ABI < 0.9 or > 1.3.

Professional online courses with cross‐referenced, multimedia content on the principles of the basic and clinical science of wound prevention and healing could augment medical education and alert medical students, PCPs, nurses, and vascular and other specialists to screen for PAD and engage patient participation in PAD risk management. Considerable research supports the role of “gamification” in patient and medical professional education that could be applied to PAD screening, diagnosis, and management.116 Integrating these education programmes into community settings could increase patient awareness and adherence to PAD management principles across home or long‐term care, skilled nursing facilities, and assisted living and long‐term acute care settings in partnership with PCP's managing patients in all living venues.

5.3. Limitations

The quality of the study was not assessed systematically in this scoping literature review. Studies frequently had small sample sizes or did not describe evaluation blinding. There was a noticeable trend for the more invasive PAD screening or diagnostic tools to be used only on patients with CLI or more severe levels of PAD, so their relevance remains untested as screening tools for PAD in the general population. Finally, some diagnostic tests generate higher false‐positive PAD identification for individuals with non‐significant arterial lesions.42 Caution should be exercised in interpreting results of those tests. Additional supporting non‐invasive tests are advised to inform management decisions.

5.4. How patients and clinicians behave—help or hinder each other

Inadequate protocols for the grass root diagnosis of PAD, MVU, and VLU seem to be at the heart of the problem of early diagnosis. There appears to be a common failure, after the history and physical examination, to adequately assess patient PAD with non‐invasive studies, as there are often no clinical signs of ischaemic pain or ALU or MLU.117

Historically, patients may fail to receive proper first‐tier non‐invasive vascular testing due to lack of PCP time or equipment or patient transportation limitations in getting to the vascular specialist or vascular testing centre. Another reason for delayed referral is that guideline criteria for referral can differ, confusing PCPs about when to refer patients to a wound or vascular specialist. Pulse evaluations can be equivocal and ABI's can produce false normal values, for example, results over 1.3, which may suggest calcified arterial walls reflecting significant PAD. Some specialists suggest that the TBI reduces potential false negatives of the ABI in these cases.118 Once the PCP identifies likely PAD based on pulse and ABI evaluations, standardised treadmill or walking distance testing in the PCP office or by referral is valid and reliable in confirming PAD diagnosis.86, 87, 88, 89, 90, 91, 92, 93

An Arterial Duplex Doppler is rarely available in the PCP setting, so some vascular specialists send a vascular technician to the point of care with non‐invasive testing instruments, for example, Arterial Duplex Doppler to screen for need for a consultation in the vascular specialist's office. One successful model centres the patient and PCP as a hub for all appropriate referrals, with consistent high‐quality referral care and measured feedback about progress in each area of patient need, such as supervised exercise by a physical therapist, nicotine and blood lipid reduction, meticulous foot and nail care, revascularisation, and so on. Given patient mobility issues associated with the PAD progression to CLI, adequately equipped mobile multidisciplinary teams including vascular and other appropriate specialists that deliver regular high‐quality community care to patients in broader care settings, such as community centres, senior social gatherings, or the “Leg clubs”119 may help stem the tide of PAD progression to CLI, amputation, and death.

Having a vascular technologist act as a liaison between the community PCP and vascular specialist could also streamline PAD communications and thorough testing to inform prompt, effective management decisions. This would optimise assessment, care, and feedback about patient PAD status, reducing PCP staff time pressure and expense of testing equipment, while improving reliability of pulse evaluation and ABI (or TBI) measurement by a trained specialist. Besides the diagnostic and therapeutic benefit to the PCP and patients, this model is financially balanced, offsetting PCP expenses for specialist services by office rental fee to the specialist for a defined number of technician hours per month.

6. CONCLUSIONS

Sufficient evidence supports reliability and validity of ABI <0.9 for use in screening all high‐risk patients over 50 years of age for PAD at routine physical examinations before PAD thickens arterial walls. The broad and consistent use of this screening test in community care could promote earlier screening and referral to specialists for detailed diagnosis using reliable, valid haemodynamic, arterial imaging, or walking distance objective tests to inform PAD disease management decisions. This approach could mobilise multidisciplinary teams to improve patient outcomes and combat this pervasive, stealthy killer.

Donohue CM, Adler JV, Bolton LL. Peripheral arterial disease screening and diagnostic practice: A scoping review. Int Wound J. 2020;17:32–44. 10.1111/iwj.13223