Who is responsible for the care of patients treated with warfarin therapy?

To identify potential weaknesses in the system of managing warfarin therapy.

A structured interview-based study of 40 community-dwelling patients taking warfarin and with an international normalised ratio > or = 6.0 and 36 of their treating doctors (35 general practitioners and 1 specialist), conducted between July and November 2007. Patients all received services from and were recruited sequentially by a large, private metropolitan pathology provider in Melbourne.

Patients' demographic, clinical, cognitive and psychosocial characteristics, warfarin knowledge, medication complexity and adherence; and doctors' experience with, approach to and involvement in warfarin management, and their perception of responsibility for warfarin management and patient education.

Interviews revealed multiple difficulties, including cognitive dysfunction, possible depression, and medication non-adherence, in 30 of 40 patients. Of 36 doctors interviewed, 12 were unaware of these difficulties in their patients. Five doctors considered they had sole responsibility for their patients' anticoagulation, while 15 confirmed a mutual relationship with the pathology service, and 16 deferred total responsibility to the pathology provider. Only 14/36 doctors reported conducting patient education at commencement of warfarin therapy, with the other 22 stating this was the responsibility of the initiating specialist, pathology service or dispensing pharmacist.

There is a need for improved role clarification in coordinating warfarin management. We propose exploring the possibility of a Warfarin Suitability Score to assist better recognition of patients in whom treatment may be problematic, along with a model of care using practice nurses with GPs to facilitate optimal patient care.