Plain English Summary
Background and study aims
Peripheral arterial disease (PAD) is a common condition in which the blood flow to the legs is restricted. This happens because of the buildup of a fatty substance (plaque) and calcium salts on walls of arteries, which becomes hardened (calcification) leading to reduced flow of blood through the blood vessels. Over time this can cause the main arteries in the legs to become narrowed (stenosed). This can cause a severe cramping pain in the legs when exercising (claudication), as the restricted blood flow cannot deliver enough oxygen to the leg muscles. Eventually, the arteries can become completely blocked, cutting off the blood supply and leading to ulcers and gangrene, which can result in amputation. Detecting PAD early allows its risk factors to be controlled but currently there are no devices which general practitioners can easily use to diagnose PAD. The Ankle Brachial Pressure Index (ABPI) test has been recommended but is time consuming and few healthcare professionals have been properly trained in the technique. The test works by comparing the pressure of blood in the arteries in the arms and legs – if the measurement in the leg is lower than the arm then this means that the arteries are likely to be blocked. This study will test a newly developed PAD detector device called MPPG which is comfortable for patients and easy to use in any clinical setting. Initial studies have indicated that it substantially agrees with the currently recommended ABPI assessments. The aim of this study is to evaluate that the MPPG is as good if not better than ABPI in a GP clinic setting.
Who can participate?
Adult patients with PAD and healthy adults without PAD.
What does the study involve?
All participants attend an appointment at their local GP practice. At the appointment, the ABPI is undertaken. This involves having a blood pressure cuff inflated around the calf and slowly deflated as a small ultrasound probe is used to detect the pulse from two places on the foot. These values are then used, along with blood pressure measurements taken from the arms, to calculate the ABPI. Next, participants undergo the MPPG test. This involves small blood flow sensor clips being gently attached to specific peripheral sites and the pulses measured for analysis. Patients finally undergo a duplex ultrasound scan of both legs, whiwhich shows up significant blockages. Duplex ultrasound is currently the best way of measuring whether arteries are blocked (a gold or index standard). The ability of the ABPI test and MPPG test for diagnosing PAD is then compared to the results of the ultrasound scan.
What are the possible benefits and risks of participating?
There is no direct benefit to participants in this trial. However, findings in this study will contribute to further understanding of this disease and potentially lead to earlier diagnosis of PAD in the future. There are no notable risks involved with participating in this study.
Where is the study run from?
Royal Victoria Infirmary (UK)
When is the study starting and how long is it expected to run for?
February 2015 to January 2017
Who is funding the study?
National Institute for Health Research (UK)
Who is the main contact?
Mr Michael White
Innovative photoplethysmography technology for rapid non-invasive assessment of peripheral arterial disease in primary care (NOTEPAD)
The aim of the study is to evaluate the performance of innovative MPPG photoplethysmography technology when diagnosing peripheral arterial disease (PAD) in comparison to ankle brachial pressure index (ABPI) when used in a GP setting.
North East - Newcastle & North Tyneside 1 Research Ethics Committee, 13/01/2015, ref: 14/NE/1238
Observational case-control diagnotic accuracy study
Primary study design
Secondary study design
Patient information sheet
Not available in web format, please use the contact details below to request a patient information sheet
Peripheral arterial disease (PAD)
GP Practices will identify eligible patients and send invite letters in the post. Once an invite is accepted, the GP Practice will match the PAD patient with a control (matched by age and sex) and send out another invitation. At this stage, the NOTEPAD team and GP Practice will work collaboratively to arrange a clinic. When a patient attends this clinic, they will first be consented and then be asked to do a short questionnaire. They will then be invited for ABPI and MPPG measurements (order is randomized). These procedures will take approximately 45 minutes. A Duplex ultrasound scan of the legs will then be performed to provide a reference standard for PAD, this will take a further 45 minutes.
Once these three measurements are complete the patient will be free to leave and no follow ups are required.
ABPI (current recommended standard test): A portable Doppler ultrasound probe is used to measure the systolic blood pressures in the posterior tibial and dorsalis pedis arteries for each foot, with the probe detecting the return of the pulse at each site during careful ankle blood pressure cuff deflation. The brachial systolic pressures for the right and left arms are measured the same way and then the ABPI is calculated (with normal range between 0.9 and 1.3).
MPPG (index test): Small optical sensor clips are gently attached to specific finger, toe and ear sites to detect the blood flow pulses.
Duplex ultrasound scan (reference standard test): Participants will have a duplex ultrasound scan performed on both legs by a vascular scientist.
Primary outcome measures
Diagnostic accuracy of MPPG and ABPI with each compared with Duplex scan using values of sensitivity, specificity, and positive and negative predictive values.
Secondary outcome measures
No secondary outcome measures.
Overall trial start date
Overall trial end date
Participant inclusion criteria
1. Aged 45 years and over
2. Provision of informed consent
3. Diagnosed with PAD
1. Aged 45 years and over
2. Provision of informed consent
3. Not diagnosed with PAD
Target number of participants
Planned Sample Size: 250; UK Sample Size: 250
Participant exclusion criteria
1. Those under 45 years of age
2. Those unable to provide informed consent.
3. Individuals with renal failure receiving renal support therapy (ESRF)
4. Patients with tender or painful calves, ankles or feet who would be unable to tolerate ABPI measurements (ulcerated legs)
5. Toe/limb amputees (bilateral comparisons needed to make pulse and pressure-based assessments)
6. PPG measurement site (big toe pad, index finger pad, earlobe) having any visible damage to local skin area (skin needs to be intact)
7. Significant limb tremor
8. Patients unable to understand English sufficiently to give informed consent
Recruitment start date
Recruitment end date
Countries of recruitment
Trial participating centre
Royal Victoria Infirmary
Leazes Wing Queen Victoria Road
Newcastle Upon Tyne
Newcastle upon Tyne Hospitals NHS Foundation Trust
Northern Medical Physics and Clinical Engineering
Newcastle upon Tyne
National Institute for Health Research
Funding Body Type
Funding Body Subtype
Results and Publications
Publication and dissemination plan
Study results will be shared widely and in particular will be disseminated to GP Practices, Vascular Surgical Groups and vascular disease charities. It is also planned to publish articles and present the findings of this research to scientific conferences. It is envisaged that findings will be disseminated through the media.
Intention to publish date
Participant level data
Not provided at time of registration
Results - basic reporting