Plain English Summary
Background and study aims
Oral anticoagulant (blood thinning) drugs are very useful for treating and preventing blood clots. However, with them comes a risk of bleeding if the blood gets too “thin” (too slow to clot). Currently, warfarin is the most commonly used drug for treating/preventing blood clots, however dosages must be closely monitored as it can cause several severe side effects, such as making people more prone to bleeding. A new generation of anticoagulant drugs have become available which are believed to be safer than warfarin. It is already known that people who eat little vitamin K (a vitamin mainly found in green leafy vegetables which plays a key role in blood clotting), are very sensitive to the blood-thinning effect of warfarin. However, it is unknown whether these people would also more sensitive to the new drugs. Tests in animals have shown that those with little vitamin K in their diets were more sensitive to the new drugs, however as yet, no one has checked whether this is the same in humans. This study is looking at whether the blood-thinning activity of two new drugs (dabigatra and rivaroxaban) is influenced by how much vitamin K we eat.
Who can participate?
Thirty patients over the age of 65 suspected of even little vitamin K and thirty patients under the age of 65 with healthy, balanced diets.
What does the study involve?
All participants are asked to complete a questionnaire about the foods that they have eaten over the last week. A sample of blood is then taken through a vein which is tested in the laboratory for vitamin K levels and how much clotting factor is present (proteins that control bleeding) so that the clotting time between the two groups of patients can be compared.
What are the possible benefits and risks of participating?
There are no direct benefits involved for those taking part in this study. There is a small risk of pain, bruising or bleeding during and after blood samples are taken.
Where is the study run from?
Royal Victoria Infirmary (Newcastle)
When is the study starting and how long is it expected to run for?
September 2013 to April 2018
Who is funding the study?
NIHR Newcastle Biomedical Research Centre (UK)
Who is the main contact?
Professor Farhad Kamali
Investigation of the effect of vitamin K deficiency on anticoagulant response to novel oral anticoagulants (direct thrombin inhibitors and FXa inhibitors) ex-vivo
Vitamin K deficiency enhances anticoagulation response to new generation of oral anticoagulants.
NRES Committee North East- Newcastle & North Tyneside 2, 18/05/2016, ref: 12/NE/0209
Single-centre observational cohort 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.
The study will recruit 30 subjects suspected of low dietary vitamin K intake (elderly inpatients not on warfarin), 30 elderly medically stable subjects (inpatients not on warfarin) with healthy diets, and 30 healthy younger subjects with adequate dietary vitamin K intake.
All subjects will complete a validated simple questionnaire (FFQ) which records their food intake of vitamin K containing foods on average and over the past week. A sample of 20 ml fasting venous blood is then taken for later laboratory tests Plasma fasting vitamin K levels will be measured as an indication of subjects’ dietary status. Activated partial thromboplastin time (aPTT), prothrombin time (PT) and modified PT will be measured in plasma incubated with rivaroxaban (100-500ng/ml). The kinetics of thrombin formation in plasma in the presence of drug will be determined using the endogenous thrombin potential (ETP) test.
Primary outcome measure
Secondary outcome measures
No secondary outcome measures
Overall trial start date
Overall trial end date
Reason abandoned (if study stopped)
Participant inclusion criteria
1. >65 years old
2. Medically stable
3. Without liver dysfunction
4. Able to give informed consent
5. Suspected of vitamin K deficiency as evaluated by the use of dietary questionnaire
1. <65 years of age
3. Having a normal healthy diet as evaluated by the dietary questionnaire
Target number of participants
Participant exclusion criteria
1. Less than 18 years of age
2. Liver dysfunction
3. Receiving anticoagulation therapy
Recruitment start date
Recruitment end date
Countries of recruitment
Trial participating centre
Royal Victoria Infirmary
Newcastle upon Tyne
Newcastle upon Tyne Hospitals Foundation Trust
Royal Victoria Infirmary
Newcastle upon Tyne
NIHR Newcastle Biomedical Research Centre
Funding Body Type
Funding Body Subtype
Results and Publications
Publication and dissemination plan
Research output (publications, conferences and presentations), and educational materials for patients and health professionals involved in anti-coagulation management, including GPs and hospital doctors.
Intention to publish date
Participant level data
Stored in repository
Basic results (scientific)