Phenylketonurias, Cardiovascular Diseases
Conditions
Keywords
PKU, CVD, Cardiovascular disease risk
Brief summary
This study will assess the cardiovascular disease (CVD) risk in Phenylketonuria (PKU) patients on a low-phenylalanine diet (LPD). Ultrasound tests, diet information and routine blood samples will be collected once per patient at their next outpatient appointment. 32 adults with PKU will be studied and compared to reference data for healthy people. The results will show if the PKU CVD risk differs from healthy people, and if CVD risk varies within people with PKU.
Detailed description
Cardiovascular disease (CVD) is the largest cause of deaths worldwide each year. Many factors affect CVD including diet, genetics, exercise and smoking. It is unclear if Phenylketonuria (PKU) and the low-phenylalanine diet (LPD) affect CVD risk. CVD risk can be predicted by measuring the thickness of the artery wall in the neck which supplies blood to the head. Thickness is measured using a non-invasive, safe ultrasound test (similar to pregnancy jelly scans). A wall thicker than normal indicates an increased CVD risk. A wall thinner than normal indicates a lower CVD risk.
Interventions
DIAGNOSTIC_TESTCarotid intima media thickness measurement (CIMT)
CIMT is a measurement of the thickness of the two inner layers of the common carotid artery wall. Using ultrasound, a linear array transducer is placed on the surface of the skin at the neck. Electrocardiogram(ECG) electrodes are placed on each wrist and one on the ankle. An image of the common carotid artery (CCA) is then produced in anterior, posterior and lateral views, and saved along with the ECG recording. The wall thickness can then be measured at the same point in the cardiac cycle using semi-automated detection software (Philips QLAB), which can reduce observer variability. The CIMT will be averaged across left and right CIMTs, as the control reference values use an average of both sides.
DIAGNOSTIC_TESTPulse Wave Velocity measurement
The PWV measures the speed of a pulse wave travelling between two points in the vascular systems of known distance between them. PWV will be measured by the gold standard carotid-femoral PWV method which is a direct measurement of aortic stiffness. A 3-Lead ECG is connected alongside measurements of the blood velocity trace for the left CCA 2cm proximal to the bifurcation, and for the left common femoral artery origin.
DIAGNOSTIC_TESTAnkle-brachial pressure index (ABPI)
A blood pressure cuff is placed around the ankle and upper arm of the participant. A continuous wave Doppler probe is used over the surface of the skin to locate the artery distal to the cuff (such as the brachial artery in the arm, or the anterior tibial and posterior tibial arteries in the ankle). The cuff is then inflated, and the systolic pressure identified by listening cessation of the sounds produced by the probe corresponding to blood flow in the artery. The ABPI is then the ratio of the highest systolic ankle pressure divided by the highest systolic brachial pressure for the left and right sides of the body.
OTHERDiet questionnaire and diet diary
Dietary information will be collected in two formats. One will be a 14-item questionnaire (Martínez-González et al., 2012), which is a simplified version of a comprehensive food frequency questionnaire. This provides a quick measure of compliance to a Mediterranean dietary pattern and a rough measure of protective and adverse dietary factors that could affect individual CVD risk. The second will be a 3-day diet diary (3DDD). This will consist of participants recording the foods that they consume and the quantities, which will then be analysed for macro- and micronutrient composition once completed.
OTHERRoutine blood samples
Blood samples will be taken from participants during their outpatient appointment. Patients routinely have blood samples taken during this clinic. The study will use the results from the routine blood tests, and also extra blood samples to collect data on other biomarkers. The laboratory facilities at Guy's and St Thomas Hospitals will be used to conduct analysis, no other laboratories will be used. Data will be collected on Phenylalanine levels, lipids, vitamin B12 and related biomarkers.
Sponsors
Guy's and St Thomas' NHS Foundation Trust
Study design
Observational model
CASE_CONTROL
Time perspective
CROSS_SECTIONAL
Eligibility
Sex/Gender
ALL
Age
18 Years to 60 Years
Healthy volunteers
No
Inclusion criteria
* Phenylketonuria patients at Guys and St Thomas' Centre for Inherited Metabolic Diseases, who have a diagnosis of Phenylketonuria at birth (following the introduction of the newborn screening programme), and who are over the age of 18 will be invited to take part in the study. * The study will only include patients diagnosed at birth, which will allow a better assessment of the effects of the diet, which are not influenced by a late diagnosis and a prior diet which is not low-Phenylalanine.
Exclusion criteria
* Phenylketonuria patients at Guys and St Thomas' Centre for Inherited Metabolic Diseases, who have a diagnosis of Phenylketonuria after birth (not diagnosed during newborn screening), will be excluded from taking part in the study. * If patients are pregnant, or plan to be pregnant during the study they will also be excluded. * Patients with a previous history of cardiovascular disease, and/or a history of cardiovascular disease in their immediate family will also be excluded. * Patients that are unable to understand and consent to the study (i.e. due to language issues or lacking capacity) will also be excluded.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| A single carotid-intima media thickness (CIMT) measurement in Phenylketonuria (PKU) participants and the corresponding age- and gender-matched controls. | 10 minutes | A single CIMT measurement in PKU participants at their most recent outpatient appointment, and the corresponding age- and gender-matched CIMT, generated from the male (1) or female (2) equation for a healthy population using each participants' age and gender (Engelen et al., 2013). |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Ankle brachial pressure index (ABPI) | 10 minutes | will be compared to PKU patient biomarkers (median annual Phe levels, biomarkers and dietary factors) to assess if there is any correlation between compliance to diet and variation in cardiovascular risk within PKU patients. |
| Vitamin B12 levels from blood sample | 5 minutes | will be compared to PKU patient measures (PWV, ABPI and CIMT) to assess if there is any correlation between compliance to diet and variation in cardiovascular risk within PKU patients. |
| Pulse Wave Velocity (PWV) | 10 minutes | will be compared to PKU patient biomarkers (median annual Phenylalanine levels, biomarkers and dietary factors) to assess if there is any correlation between compliance to diet and variation in cardiovascular risk within PKU patients. |
| Blood low-density lipoprotein (LDL) cholesterol levels | 5 minutes | will be compared to PKU patient measures (PWV, ABPI and CIMT) to assess if there is any correlation between compliance to diet and variation in cardiovascular risk within PKU patients. |
| Diet diary and diet questionnaire (Mediterranean Adherence Screener, 0-14 scale, 14 indicating full adherence, 0 indicating no adherence) | 3 days | will be compared to PKU patient measures (PWV, ABPI and CIMT) to assess if there is any correlation between compliance to diet and variation in cardiovascular risk within PKU patients. |
| Blood Phenylalanine levels | 5 minutes | will be compared to PKU patient measures (PWV, ABPI and CIMT) to assess if there is any correlation between compliance to diet and variation in cardiovascular risk within PKU patients. |
Countries
United Kingdom
Contacts
Primary ContactRadha Ramachandran
Backup ContactSam Dicken
Outcome results
None listed