The IMPACT Study (Pulse Wave Velocity follow-up study)
Research type
Research Study
Full title
A comparison of artery health in patients with and without psoriasis: A follow-up study
IRAS ID
148478
Contact name
Christopher Griffiths
Contact email
Sponsor organisation
Salford Royal Hospitals NHS Trust
Research summary
Previous studies have suggested that people with psoriasis are more likely to experience cardiovascular events such as heart attack and stroke than people without psoriasis. It is unclear whether psoriasis is an independent risk factor for cardiovascular disease or if the increased risk is explained by shared risk factors. One hundred and eighty-three people with psoriasis, identified by their General Practice have previously participated in two linked studies; IMPACT study, a cardiovascular screening study for people with psoriasis (11/NW/0654) and a pulse wave velocity sub-study associated with this study (12/NW/0239).
Pulse wave velocity is a measure of arterial stiffness and is related to the future risk of having a heart attack or stroke. The pulse wave velocity sub-study aims to assess whether pulse wave velocity is independently related to a) the presence and b) the severity of psoriasis. Data in people without psoriasis has been collected in another study.
After appropriate training, pulse wave velocity data was collected by four research nurses (observers) using three identical arteriograph machines. At the end of the data collection period, further observer reliability testing revealed no significant differences in measurements between machines but an important and significant difference in between-observer measurements. Our data showed that these measurement errors were accounted for by between-observer variation in the measurement of jugular symphysis distance. This manual measurement, between the suprasternal notch and the symphysis pubis, was taken by the nurses using callipers.
Our validation exercise has shown large inter-observer variation in the measurement of jugular symphysis distance that will interfere with the quality of the pulse wave velocity data. Knowing this, re-measurement by a single observer is crucial to the quality of the study. A 2 cm error in the measurement of jugular symphysis distance for an individual will produce a 4% error in the value of pulse wave velocity. This could lead to an 8% error in the difference between individuals. The expected difference in pulse wave velocity between study groups, for example, between individuals with and without psoriasis, is likely to be around 10%. Therefore, with the observed measurement error, we may fail to show differences between groups when real differences exist, and conversely we may falsely show differences between groups when no real differences exist.In this study we propose to re-measure jugular symphysis distance in all participants of the pulse wave velocity sub-study using one observer to reduce observer error. Jugular symphysis measurements can be re-entered into software to calculate the pulse wave velocity measurement.
We plan to use these recalculated values for pulse wave velocity in our analysis assessing whether a) the presence or b) severity of psoriasis independent risk factors for vascular stiffness.
REC name
South Central - Oxford A Research Ethics Committee
REC reference
14/SC/0119
Date of REC Opinion
24 Mar 2014
REC opinion
Further Information Favourable Opinion