An average practice of 2,000 patients will have between 20-40 patients with atrial fibrillation (AF). In rural practices with a higher percentage of older people, this can be significantly greater.¹ The numbers with AF are set to rise, and many commentators expect a doubling in numbers by 2020, as a result of an ageing population and increased survivors of heart disease. 

Using the CHA2DS2-VASc score as a risk assessment means that the vast majority of these older patients would be recommended for oral anticoagulation.² The results from clinical trials assessing the reduction in stroke when patients are effectively anticoagulated have been validated in clinical practice.^1,3

Oral anticoagulation with warfarin is currently the gold standard treatment for reducing the risk of stroke in AF.⁴ The rate of stroke in AF without anticoagulation is about 1% per annum in those with no risk factors, rising up to near 18% with the highest risk. Anticoagulation reduces the risk of stroke by up to 70% and has greatest effect in those with the highest risk.¹

Treatment with warfarin requires careful monitoring and considerable resources if undertaken in primary care. The novel anticoagulant dabigatran is licensed to prevent thromboembolic stroke in patients with AF and has been demonstrated to have greater efficacy at lower risk. More recently, rivaroxaban has been approved for a similar indication. This is a challenge for the HSE in terms of reimbursement issues.⁵

While there is a perception that GPs are not anticoagulating enough of their patients with AF, it has been demonstrated that when clinically indicated, the vast majority are offered and given appropriate anticoagulation.⁶

Factors that may lead to low rates of anticoagulation may be underdiagnosis, doctor reluctance to commence warfarin in the frail elderly and patient preference not to have serial blood testing. The biggest obstacle is not clinical but resource allocation, which is not delivered in the current HSE contract. 

Anticoagulating 25 people to target will require a minimum of 15-20 minutes per patient (eight hours of manpower each month). This work is shared between doctor, nurse and administration but is a considerable commitment for GPs currently providing the service and where anticoagulation is currently managed in secondary care, a barrier to transfer of care to the community. This needs to be addressed if general practice is to deliver in this area in the future.

It has been shown that when elderly patients with AF are given the facts regarding the risk of stroke and the potential for risk reduction offered by warfarin, most will accept oral anticoagulation therapy despite its inherent risk of increased bleeding. Anticoagulation could be completely managed in primary care if adequate resource allocation was provided. 

There is thus potential to provide an improved service for patients, with better anticoagulation control, improved patient safety and a potential reduction in dosing errors.

Setting up an anti-coagulation service 

Patient identification

Most patients on anticoagulants will be known to the practice either from repeat manual scripts or by a computer search of anticoagulant drugs. Once identified, it is good practice to review the original indication, the required length of anticoagulation treatment and decide on the appropriate target INR.⁷

Errors at this stage will reveal the occasional person whose indication for anticoagulation has time elapsed or they may be at inappropriate INR target (usually too low). 

In most practices there will be some patients with AF, currently not taking anticoagulation, who should be considered for intervention. These may be identified from morbidity registers or by a search for rate-controlling drugs, eg. digoxin and beta blockers. 

An average practice should expect the prevalence for oral anticoagulation to be around 1-2%, but this could be double in ‘older’ rural practices.

Workload and staffing issues

The amount of clinic time required to run an anticoagulation service is proportional to the number of patients and the interval of testing required. With 100 patients being tested at four weekly intervals, 8-10 hours clinic time/week will be required.

Computerised decision support software can reliably increase the average review period without reducing the quality of anticoagulation control; however it is not essential for high quality practice, and written algorithm-based adjustment works well.⁷

Staff training will need to cover: 

• Basic theory of anticoagulation. The clinical aspects regarding the use of warfarin: side-effects, contraindications, interactions and dosing schemes.
• Patient education regarding warfarin use and interactions. Use of patient information leaflet
• Detailed training on the use of near-patient testing apparatus in use, eg. Coaguchek™ system
• Practice protocol for the clinic, including practicalities, eg. details of who to ask if there is a problem with equipment, what to do when INR out of range etc
• Call and recall system for testing
• A health and safety statement specific to the anticoagulation clinic with references to safe venesection or finger-prick testing, sharps disposal, preventing and managing needlestick injury, hepatitis B vaccination status, etc.
• Quality control: How is it to be assessed and maintained? Internal controls (using control solutions) and external controls sending random samples to hospital after near-patient testing. This will require agreement with the local laboratory and may involve cost. The latest Coaguchek™ model is self-calibrating and a control is run on each strip. External annual calibration of machinery is also advised. While HIQA has yet to get involved in this setting, it is highly likely that it will introduce standards for the accurate calibration of near-testing equipment used in general practice in the not too distant future. Currently, UK NEQAS provide verification of standard which costs €220 per annum
• Appropriate record-keeping and audit procedures must be in place. It is advisable to have a separate manual log of all patients on anticoagulation with details of dosage, test results in addition to results in the computer file and the patient-held record. Audit will be an essential component of the service and will assess outcomes of anticoagulation, eg. the amount of time that each patient has an INR within therapeutic range or, by point prevalence, the proportion of patients with INR results that are within, above or below the therapeutic range at any given time. Other aspects of the anticoagulation service looking at adverse reactions and complications, eg. thrombosis or bleeding, can be monitored as part of an audit or critical event analysis.

A lot of good advice is contained in the Quality in Practice publication on the use of warfarin in general practice. This is published by the ICGP and downloadable from its website (www.icgp.ie).⁷

While not suitable for all, self-monitoring is now a real option for patients, with decreased cost and increased accuracy of near-patient testing devices. In suitable candidates, self-management has been shown to improve both the quality of anticoagulation and reduce bleeding side-effects.⁸ Set up costs will vary depending on whether a GP purchases equipment for near-patient testing or opts to use a laboratory service and courier to transport samples. 

A Coaguchek™ machine costs over a €1,000 and the cost of each strip is about €5. Currently, strips are not reimbursable by the HSE so all patients will have to be charged a fee to cover costs. Ongoing costs will include: the cost of consumables; the cost of professional time of doctors, nursing staff and administration time; annual maintenance cost of software analysis tools if used; and the quality control costs.

All these costs must be built into the fee structure for patients.

In summary, anticoagulation can be part of structured care in general practice. It requires planning, organisation and has inherent set-up and recurring costs. Patients are generally very satisfied with the service, which is immediate, continuing, personal and delivered locally. The biggest barrier to implementation on a nationwide basis is the lack of resources. Consideration should also be given to self-management when feasible.

The days of warfarin in anticoagulation may be numbered and the novel anticoagulants are likely to succeed it eventually, when cost-effectiveness as well as clinical efficacy is proven. But for the time being, warfarin remains a vital component of stroke prevention in AF. 

References

1. Mant J et al. Warfarin versus aspirin for stroke prevention in an elderly community population with atrial fibrillation (the Birmingham Atrial Fibrillation Treatment of the Aged Study, BAFTA): a randomised controlled trial. Lancet 2007; 370(9586): 493-503
2. Van Staa TP, Setakis E, Di Tanna GL, Lane DA, Lip GY. A comparison of risk stratification schemes for stroke in 79,884 atrial fibrillation patients in general practice. J Thromb Haemost. 2011; 9(1): 39-48
3. Evans A, Kalra L. Are the results of randomized controlled trials on anticoagulation in patients with atrial fibrillation generalisable to clinical practice? Archives of Internal Medicine 2001; 161: 1443-1447
4. Saxena R, Koudstaal PJ. Anticoagulants versus antiplatelet therapy for preventing stroke in patients with nonrheumatic atrial fibrillation and a history of stroke or transient ischemic attack. Cochrane Database Syst Rev 2004; 4
5. Should dabigatran replace warfarin for stroke prevention in AF? DTB 2011
6. Weisbord SD, Whittle J, Brooks RC. Is warfarin really underused in patients with atrial fibrillation? J Gen Intern Med 2001; 16: 743-749
7. Kildea-Shine P, O’Riordan M. Warfarin in General Practice: Quality In Practice Committee ICGP, 2009
8. Heneghan C et al. Self-monitoring of oral anticoagulation: a systematic review and meta-analysis. Lancet 2006; 367: 404-11