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Anticoag monitoring in general practice

Peggy Johnson
MRPharmS MSc PGDip ComPharmHC
Practice Pharmacist
Well Street Surgery

We have all come across patients who have expressed dissatisfaction with the inconvenience and the long waits in hospitals. However, advances in technology mean that certain tests and conditions that require ongoing monitoring are no longer confined to a laboratory or hospital setting.
An excellent example is the development of near-patient testing (NPT) or point-of-care testing (POCT) in anticoagulation monitoring at the primary care level. This involves checking the patient's INR (international normalised ratio) with a reliable, simple-to-use coagulometer (CoaguCheck S, CoaguChek XS, ProTime, SmartCheck INR) and dosing the patient with support from computerised decision support software (CDSS).
NPT or POCT is defined as any analytical test performed for a patient by a healthcare professional outside the conventional laboratory setting. The advantages are easier accessibility, rapid results and portable equipment.(2)
CDSS is a computer software programme that provides guidance on warfarin dosing by using a formal algorithm or mathematical equation as a basis for calculating the warfarin dose based on the INR reading. Wilson and James showed that dosing using CDSS resulted in a decrease in the percentage of blood results out of range when compared with the manual dosing system.(3) It also provides the basis for administering a reliable, effective anticoagulation clinic in primary care, with consultation and auditing being the key facilities.

Anticoagulation monitoring
An anticoagulant is an agent that prolongs the clotting time, and its effect is monitored by measuring the INR. In the UK, the main agent used as oral anticoagulant therapy (OAT) is warfarin. It is prescribed in conditions relating to venous thromboembolism (DVT, PE, recurrent DVT/PE), antiphospholipid syndrome, atrial fibrillation, mechanical prosthetic heart valves and other cardiac diseases. The target INR and the treatment duration are dependent on the indication.(4,5)
There are many factors that can affect warfarin control, namely coprescribing medications that interact with warfarin, comorbidities, certain food and supplement intake, changes in alcohol consumption and changes in the patient's physical condition.(5) Coupled with its complex pharmacokinetics, the monitoring periods are kept to a minimum. In City and Hackney, stable patients are given as a maximum an eight-weekly review.(1)
In summary, patients on OAT need to be monitored regularly in order to maintain their INRs within their INR target range, to ensure that the blood is sufficiently anticoagulated to prevent any clot formation, and at the same time to ensure they have not been overanticoagulated and hence at risk of having a bleeding event.
Traditionally, anticoagulation monitoring is undertaken in secondary care. However, with the increasing number of elderly patients requiring OAT, more and more primary care trusts,(1) GP practices(1,6) and community pharmacists(7,8) are working with secondary care to transfer suitable patients to primary care monitoring to provide a level 4 service (ie, sampling, testing and dosing patients according to locally agreed protocols).
Establishing a safe and effective primary care-based anticoagulation clinic
The advantages of a practice-based anticoagulation clinic are better knowledge of concomitant disease and drug therapy of the patient and better continuity of care. Most patients, and their carers, welcome the convenience of a local clinic, reducing long waiting times to hospital and travelling costs. It also helps to reduce the ever-increasing demands on existing hospital clinics. Other advantages include improved disease control and greater patient awareness and motivation.(6)
Appropriate training, competency, effective communication and good administration are regarded as the keys for effectiveness and efficiency.

Training requirement
It is paramount that the clinic should only be managed by trained staff. They must have attended an accredited training course for anticoagulation management in primary care, covering topics such as an introduction to OAT; the INR and how it is derived; the target INR (including how it relates to the diagnosis and any action that needs to be taken if the results are outside limits); an understanding of the specific NPT method for deriving INR; how to set up and maintain the coagulometer and to perform the test; the internal and external quality control procedures; how to use the CDSS programme confidently; the clinical guidelines and clinic procedures; and lastly the health and safety issues.

All personnel involved in the anticoagulant service  should be aware of their own responsibility and professional accountability and should undertake the clinic procedures only if they feel competent to do so. BCSH recommends that the personnel should be approved.(4) Indeed, in City and Hackney, the CHtPCT undertakes the competency assessment visits.

Effective communication
Communication must start at the planning stage and be continual. Early liaison with the haematologist is crucial to ensure that the training requirements and the guidelines and procedures (including validating the CDSS parameters, establishing the referral procedures and quality control) are set up to meet the highest standard. Furthermore, effective routes of communication with the haematology department and the laboratory at the hospital are needed for ongoing support and advice.
The referral procedure should state clearly how patients are identified, how to confirm with the hospital that the patients are monitored in primary care, and how to refer patients back. A secure referral system is important to ensure that no patients are lost between secondary and primary care.
Effective communication with the PCT will ensure that the training and the service provision are supported and monitored and that the anticoagulation service is standardised across the PCT.
Within the GP practice, effective routes of communication between the patient, the GP, the practice staff and the anticoagulation personnel are essential. On the one hand, the anticoagulation personnel should be informed of relevant clinical changes, and on the other, the GP must be informed of adverse events and patients who fall outside the criteria for primary care monitoring. In addition, there must be a contingency plan for holiday and emergency cover.

The clinic procedures should take into consideration all the issues that have been covered so far. In addition, there must be a traceable recall system for non­attendees, an alert system for patients who have passed their monitoring and/or treatment duration, and an annual review for each patient to assess the appropriateness of continuing OAT. To summarise, a carefully written standard operating procedure (SOP) should be in place to ensure that the anticoagulation clinic is run safely and effectively, and it must be reviewed regularly.(1,6-8)

Results from Well Street Surgery
The anticoagulant monitoring service at Well Street Surgery is an enhanced service commissioned by CHtPCT. The service model was developed by a multidisciplinary cross-organisational group that included GPs, consultants, nurses, pharmacists, managers and public health professionals.
The novelty of this service is its use of web-based CDSS, which links general practices, the haematology department and the PCT, allowing for a more joined- up service as well as improved clinical monitoring and oversight.(1)
CHtPCT conducted a patient satisfaction survey as part of the Practice Annual Review last December.(9) The survey result indicated that, of the 41 responses received (response rate was 83%), 75% rated the services provided at Well Street as excellent and 92% indicated that they would not want to return to the hospital for monitoring. As for measures of therapeutic control, audit results of the Well Street clinic indicate that the point prevalence (percentage of patients' last test in range) is always above 70%, and that more than 50% of patients have their INRs more than 70% of the time in range. This compares very favourably with the standards recommended in the BCSH.(4)
In terms of adverse events, Well Street clinic has had one major and three minor events reported. The patient who suffered the major adverse event had a massive epistaxis and haemorrhaged severely, even though her INR was within her target range of 3.0-4.0. This patient required substantial hospital intervention. Following her adverse event, the GP, the consultant haematologist and the patient weighed carefully the risk and benefit for her to continue with the OAT. The final clinical decision was to continue with warfarin but to reduce the INR target range to 1.9-2.4 and limit the review period to every four weeks at the most.

Anticoagulation monitoring in primary care is far better for the patients. Advances in technology for near- patient testing devices and computerised decision support software have meant that the monitoring can be delivered easily, safely and effectively. As for the clinicians involved in anticoagulation monitoring, it is not a business without risk, but it is up to us to ensure that the risks are reduced to an absolute minimum.
As for further development in anticoagulation monitoring, patient self-testing and patient self-management is imminent, but that will be for a future discussion.


  1. Mason J, et al. Pharm Manage 2005;21(4) Available from:
  2. MDA. Management and use of IVD point of care test devices. Available from URL:
  3. Fitzmaurice DA, et al. Oral anticoagulation management and stroke prevention: the primary care perspective. Newmarket: Hayward Medical Communications; 2002.
  4. British Committee for Standards in Haematology. Guidelines on oral anticoagulation. (3rd ed) Br J Haematol 1998;101:374-87.
  5. British Committee for Standards in Haematology. Guidelines on oral anticoagulation (warfarin). (3rd ed) 2005 update. Br J Haematol 2005;132:277-85.
  6. Sheehan O, Stinson JC, Freely J. Ir Med J 2000;93(2). Available from URL:
  7. Macgregor S. Prim Care Pharm 1999;1(1). Available from: http://www.pjonline.comPrimaryCarePharmacy/199911/articles/anticoagulati...
  8. Coleman B, et al. Pharm J 2003;207:308-11.
  9. CHtPCT. Anticoagulation clinic: patient survey results. Survey conducted September-December 2005.