Number of distal limb and brachial pressure measurements required when diagnosing peripheral arterial disease by laser Doppler flowmetry

Toe Pressure Measurements in Patients Suspected of Critical Limb Ischemia

An objective hemodynamic assessment is mandatory to confirm Critical Limb Ischemia (CLI). Toe pressure measurement is recommended. We compared toe measurements obtained using the Laser Doppler method (LD) (PERIMED PeriFlux, Sweden) considered as the reference test, with those obtained with a portable device using photoplethysmography (PPG) (Sys Toe Atys Medical, France). A total of 93 (123 legs) patients from 3 French hospitals with a clinical suspicion of CLI were included and had measurements with each device carried out by skilled operators. PPG was unable to provide a measurement in 10 patients. Lin's Coefficient correlation concordance (CCC) and Bland and Altman's scatter plot were analyzed for the 83 remaining patients, CCC was .84 95%CI (.77-.89). For detection of CLI, Cohen's kappa was .67 95%CI (.53-.81). The PPG device is fairly reliable for toe pressure measurement in patients suspected of CLI and could be useful when LD is not available. However, it fails to deliver a measurement in approximately 10% of cases. No conclusion should be made about CLI for these patients when no measurement is obtainable and other methods should be used (LD, transcutaneous oxygen pressure) to assess perfusion of the limbs.

Bedside Toe Pressures Measurements in a Department of Vascular Surgery: A Study of Diagnostic Accuracy

OBJECTIVE

In patients with peripheral arterial disease (PAD), measurements of distal blood pressure form the basis of assessing the severity of the disease along with symptoms and objective findings. The reliability and accuracy of a fully automated bedside device (SysToe) vs. strain gauge plethysmography (SGP) in patients with low toe pressures in a bedside setting in an outpatient clinic of vascular surgery were investigated.

METHODS

This was a prospective, single blinded study carried out in compliance with the Standards of Reporting of Diagnostic Accuracy Studies. A total of 94 outpatients with symptomatic PAD in an outpatient vascular surgery clinic were included and had index measurements performed with the automated bedside device in a bedside setting by observers with no training in routine distal pressure measurements. SGP reference measurements were performed in a vascular laboratory.

RESULTS

There was agreement between modalities regarding the diagnostic classification of chronic limb threatening ischaemia (CLTI) in 79/94 (84%) patients. For detection of CLTI, Cohen's kappa was 0.57 with a sensitivity of 94%, specificity of 82%, positive predictive value (PPV) 52%, and negative predictive value (NPV) 98%. On average, the automated bedside device underestimated the pressures, compared with the SGP. The mean difference between SGP and SysToe was 9 ± 16 mmHg for right limbs and 10 ± 16 mmHg for left limbs (p < .001).

CONCLUSION

The automated bedside device showed a high sensitivity and a high NPV for excluding CLTI. However, the low PPV may result in overdiagnosis. The automated bedside device may function as a screening tool identifying patients in need of further diagnostics with more accurate equipment, for example SGP.

Peripheral arterial disease screening and diagnostic practice: A scoping review

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.

Comparison of two methods based on photoplethysmography for the diagnosis of peripheral arterial disease

AIM

To examine the interchangeability of two methods for distal pressure measurement based on photoplethysmography using a truncated or full display of the arterial inflow curve, respectively.

METHODS

Toe and ankle pressures were obtained from 69 patients suspected of peripheral arterial disease (PAD). Observer reproducibility of the curve readings was examined by blinded reassessment of the pressure curves in a randomly selected subgroup (60 limbs).

RESULTS

There were no significant differences in mean pressures between the two methods (p for all > .455). The limits of agreement for the differences were -15.0-15.4 mmHg for right toe pressures, -16.3-16.2 mmHg for left toe pressures, -14.2-15.7 mmHg for right ankle pressures, and -18.3-17.7 mmHg for left ankle pressures. Correlation analysis revealed intraclass correlation coefficients ≥0.960 for all measuring sites. Cohen's Kappa showed excellent agreement in diagnostic classification, with κ = 0.930 for the diagnosis of PAD and perfect agreement in the diagnosis of critical limb ischemia (κ = 1.000). The analysis of intra-observer variation for curve reading showed limits of agreement of -3.9-4.0 for toe pressures and -7.6-7.7 for ankle pressures for the method involving truncated display and -3.1-3.2 for toe pressures and -6.3-8.6 for ankle pressures for the method involving full display of the signal.

CONCLUSION

The present study shows minimal differences in diagnostic classification, as well as in ankle and toe pressures, between the full display and the truncated display of the photoplethysmographic pulse signal. Furthermore, the inter-observer variation was low for both of the photoplethysmographic methods investigated.