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Variability of AF guidelines

Clinical bottom line

There is considerable variation in guidelines for anticoagulant treatment for patients with atrial fibrillation. This variation is seen how guidelines are developed, and in the results if applied. When twenty UK guidelines were applied to 100 consecutive community patients with AF, the proportion recommended for anticoagulation varied from 13 to 100 patients.


R Thomson et al. Guidelines on anticoagulant treatment for atrial fibrillation in Great Britain: variation in content and implications for treatment. BMJ 1998 316: 509-513.


In 1996 various people and organisations in England, Wales and Scot land were contacted about the existence of guidelines for anticoagulant treatment of atrial fibrillation. These included regional ant national NHS bodies, professional and charitable institutions, and members of mailing lists of audit organisations. These represented purchasers and providers of healthcare and represented relevant national organisations.

Guidelines were defined as a document produced to help clinicians decide which patients should be given anticoagulant drugs. Drafts, or documents designed for single specialised units, or to provide guideance once warfarin treatment had begun were not included. Where possible, guideline developers were interviewed using a semistructured method about how guidelines had been developed.

All included guidelines were applied to 100 consecutive patients with atrial fibrillation aged 65 years or older identified in a community survey. Details of risk factors for stroke or contraindications for treatment were obtained.


The overall response rate was 66% (350/534), yielding 48 documents of which 20 fulfilled the requirements for definition of a guideline. They varied from a single page to 28 pages, and were primarily for use by general practitioners and for use in populations from 12,000 to 500,000.

Guidelines were not systematically developed. About half were developed by a group, half by a single person. About half had some outside consultation, but about a quarter had no external review. Distribution was haphazard and few had educational meetings to introduce the guideline. Only one was explicitly claimed to be evidence-based, and had outside consultations from a health economist and clinician, with external review and local consultation, with wide distribution and an educational meeting to introduce the guideline.

When applied to 100 consecutive patients, the number recommended for anticoagulation by the guidelines ranged from 13 to 100 (Figure 1). Only one patient would have had anticoagulant treatment recommended by all guidelines, but every patient would have been recommended for anticoagulation by at least two guidelines (but not the same two). Target INR values varied between 1.2 to 1.5 and 2.5 to 3.0.

Figure 1: Number of patients recommended for anticoagulation by each guideline


This is a stunning paper. It is stunningly good and important that guidelines have been assessed like this, and the methods of assessment are excellent. They examine the content and development of the guidelines, but also, and vitally, how the guidelines compare when applied to real patients.

It is also stunning that only 1 in 20 guidelines was apparently based on evidence, and that many developers were apparently unaware of much of the literature on guideline development and validity. A number had completely missed the point about what "evidence" was.

This should make us critical of uncritical guidelines. It should make purchasers and providers sit up and recognise that much of what is done in their name may be at best misguided, and occasionally frankly wrong and harmful.

How it might be done can be seen from a terrific exemplar from the same Newcastle researchers.