Microvisk Continuous Blood Donation Study

The number of patients receiving anticoagulation therapy with warfarin and other vitamin K antagonists has been rising in recent years. Increasing life expectancy is increasing the proportion of the population having conditions such as Atrial Fibrillation and venous thrombosis, where primary and secondary prevention of thromboembolic complications are best achieved with anticoagulation.

Unpredictable pharmacokinetics, widespread interactions with drugs and food and the narrow therapeutic window make closely monitoring Vitamin K antagonists a necessity. Portable point of care (POC) coagulometers which measure PT from capillary whole blood and provide an INR reading within a few minutes are already widely available throughout North American and Europe. They give comparable results when compared to laboratory based systems are popular with patients and significantly shorten the duration of clinics. In addition, the United Kingdom Department of Health has been encouraging the use of anticoagulation services in Primary Care Trusts the aim being to provide INR monitoring in community clinics and General Practice surgeries relieving pressure on hospital services and reducing inconvenience for patients.

Although coagulometers are now commercially available the Microvisk INR Testing System has been designed to have advantages, particularly in terms of test robustness, user comfort, ease of use and reduction of user error. The present trial has been designed to develop the second generation Microvisk INR Test System; blood samples will also be used to optimise manufacturing processes and verify the quality of Test Strip Lots.

• Venepuncture (Procedure): Venepuncture to collect blood samples from Patients undergoing Warfarin Therapy, additional tubes of blood drawn during normal clinical vist.
• Collection of relevant information (Other): Collect relevant information to ensure potential participant meets all inclusion/exclusion criteria.

Primary outcomes

• Ongoing development of Microvisk Technologies PT/INR products [5 years]: The Primary Outcome will be measured in terms of differences in International Normalised Ratio when the Generation 2 CoagMax system is tested against the lab benchtop analyser using the blood samples from the same donors. Those differences will be reported in terms of accuracy, precision and sensitivity to interferents.

Secondary outcomes

• The Secondary Outcome will be measured in terms of differences in International Normalised Ratio when the Generation 2 system is tested against the International Standard Method using the blood samples from the same donors. [5 years]: A master batch of test strips will be calibrated against an International Reference Preparation (rTF/09) thromboplastin. The accuracy of the master batch will be verified using patient samples.

Sex: All, ages: 18 Years to any

Inclusion Criteria:

* Currently undergoing Warfarin therapy.
* Over 18 years old

Exclusion Criteria:

A participant is not eligible for participation if ANY of the following criteria are met:

* Participant is <18 years of age
* Participant is unable to give consent
* Participant has been treated with Unfractionated Heparin, or Low Molecular Weight Heparin, within the last 7 days
* Participant has, or is suspected of having, Anti-Phospholipid Syndrome (APS)
* Participant is pregnant, or has been in the past 12 months
* Participant is known to have HIV/AIDS, is a carrier of Hepatitis A, B or C, has had tuberculosis or a tropical disease
* Participant is suspected of intravenous drug use

• Susan Shapiro, Principal investigator, Oxford Haemophilia and Thrombosis Centre Oxford University Hospital NHS Foundation Trust