GP mythbuster 92: Anticoagulant monitoring in primary care

Anticoagulant medicines are used to treat and prevent blood clots.

We consider the proper and safe use of medicines under the safe, effective and well-led key questions. The relevant key lines of enquiry (KLOEs) are:

• S4: How does the provider ensure the proper and safe use of medicines, where the service is responsible?
• E2: How are people’s care and treatment outcomes monitored and how do they compare with other similar services?
• E3: How does the service make sure that staff have the skills, knowledge and experience to deliver effective care, support and treatment?
• W5: Are there clear and effective processes for managing risks, issues and performance?

Anticoagulation can be achieved using many different medicines. Here we consider how patients taking oral anticoagulants are managed.

• It is the responsibility of the prescriber to assure themselves that it is safe and appropriate to prescribe.
• Where prescribing and management of anticoagulants is carried out by secondary care, record this in line with practice procedure for recording hospital medicines. The record should be visible when a clinician is making a decision on prescribing.

Managing patients taking warfarin

Guidance on prescribing and managing warfarin is detailed in NICE oral anticoagulation clinical knowledge summary.

Patients who take warfarin need frequent monitoring to ensure that the effect is within a safe range. Patients are usually issued with a 'yellow book'. This details their test results, their recommended dose and the date of their next test.

The practice should make sure all patients taking warfarin attend on time for measurement of their INR.

There are different models of care delivery for patients prescribed warfarin in primary care.

For example:

• The local anticoagulation service is usually based in a hospital haematology department.
  • The patient’s GP practice is still responsible for prescribing the warfarin.
  • The practice must make sure appropriate monitoring and dosing advice is in place to manage the patient safely.
  • This should be recorded in the patient record.
• The practice sends a blood sample to the laboratory for testing.
  • We expect the practice to manage the incoming test results. See GP mythbuster 46: Managing test results and clinical correspondence.
  • Include results in clinical decision making, managing the patient’s warfarin dose and deciding the monitoring interval.
• Near patient testing or point of care testing at the practice or a community pharmacy. Results are available immediately.
  • Clinical decisions about dosing and testing intervals can be made by a clinician. This may be a doctor, nurse or pharmacist with suitable training and experience
  • They could also be made by using a computerised decision support system. For example, INRstar.
• The test is often carried out by a Health Care Assistant (HCA). The HCA must:
  • be trained to carry out this role and act in line with practice policy on managing anticoagulated patients. This may allow the HCA to make dosing recommendations using a computerised decision support tool within defined parameters, or require all warfarin doses to be approved by a doctor.
  • There should be a system of audit to review consistency and accuracy of clinical decision-making.
  • Equipment must be maintained in line with manufacturer’s instructions. Records should be kept of internal and external quality assurance.
• Self-testing or self-management
  • Prescribers may assess suitable patients to carry out their own blood tests. This depends on local commissioning arrangements.

Managing patients taking direct oral anticoagulants (DOACs)

There are four DOACs available in the UK. Each has its own specific indications and dosing information. NICE oral anticoagulation clinical knowledge summary provides detail on prescribing and managing patients.

Monitoring for patients on these newer medicines is less time consuming for both patients and practices.

Periodic review is necessary to check renal and liver functions which affect the way these medicines are metabolised. It is also necessary to assess compliance and check for adverse effects such as bleeding. However, the anticoagulant effect is not monitored in the same way as warfarin.

The correct dose must be prescribed. This depends on factors such as age, weight, renal function and clinical indication. It is important that the correct calculation is used for renal function and recorded in the patient record.