Warfarin Sensitivity Testing

People vary up to 40 fold in their response to warfarin. Age and BMI are key variables together with lifestyle factors. Genetic variation is also a major contributor. Approximately 1 in 3 people have at least one variant copy of one of the two key genes. Approximately 1 in 30 people have two variant alleles of both genes. People carrying these variant alleles have reduced enzymatic activity and require lower warfarin doses. Because they are highly sensitive to warfarin, this can make achieving a stable INR within therapeutic range very difficult.

The new pathway makes pharmacogenetic testing routinely available to GPs and hospital clinicians. Using a buccal swab or blood sample, analysis can identify specific variants. The results from this test can be used to inform anticoagulant choice and dosing during loading and maintenance regimen.  This test works well for individuals of North European descent. For individuals of different descent, the traditional slow loading approach is recommended.


This project is part of the AHSN NENC Optimising Pathways for Anticoagulation in Newcastle (OPAN) Programme

In January 2018 the AHSN NENC, in partnership with Newcastle Gateshead CCG and the Newcastle upon Tyne Hospitals NHS Foundation Trust launched a novel personalised clinical pathway of anticoagulation treatment for AF patients in the Newcastle area as part of OPAN. The pathway comprises three innovations: warfarin sensitivity genotype testing before choice of anticoagulant is made, then where appropriate, genotype guided warfarin initiation, and subsequently an option for patients to self-test their INR at home.