Hopes and Aspirin-ations3 Mar 2010

An article from our January newsletter

Once again the practice nurse or GP working at the coal face has been put in a difficult position when two sets of experts offer conflicting advice.  This time it's about aspirin when recommended as a primary prevention therapy, especially in diabetes.

The theory goes something like this:

1.    Aspirin is the single most effective means of preventing people who have had a myocardial infarction from having another.
2.    If it's effective in doing this then it must be logical to go back in time and prevent this situation happening in the first place in people who are at high risk of developing or may already have sub-clinical cardiovascular disease.
3.    People with diabetes are in this position so they should be given low dose aspirin to prevent myocardial infarction.
4.    NICE recommend this course of action.

So that's alright then?

Well, no it isn't actually because the evidence doesn't support this course of action.

Two large trials have reported recently to bear out what many people already thought, that there was no benefit supporting the use of aspirin as a primary prevention measure.  Belch et al (2008) followed well over 2000 people for over four years and found that low dose aspirin did not reduce the risk of cardiovascular events.  Ogawa et al (2008) in Japan followed a similar number of people for a similar time and echoed the results.

NICE (2008) recommends the use of aspirin for the primary prevention of cardiovascular events in people with diabetes

Once again, we have a conflict similar to the one where eminent bodies recommended different target levels for blood pressure.

This put people in primary care who are trying to the best of their ability to do what is right in a very difficult position.

If they put a patient on aspirin and that person suffers a gastro-intestinal bleed, they will be asked why they prescribed the drug when it is not supported by the evidence.

If they do not put a patient on aspirin and that person suffers a myocardial infarction, they will be asked why they did not prescribe the drug when national guidelines recommend this course of action.

There are several things that are worrying about the way the research is performed and reported.  Unlike the days when DCCT reported, there now seems more incentive to publish a large number of articles rather than getting everything into one publication.  Some results are deliberately held back to provide fodder for a future tranche of articles which may provide extra kudos but do little to help a patient.

It is irresponsible of experts to produce guidelines without any regard for what other experts are recommending and consequently places the actual prescriber in a real quandry. 

It is perhaps expecting too much for bodies such as NICE to respond immediately to clear new evidence.

Belch J et al (2008) The Prevention and progression of arterial disease and diabetes trial (POPADAD) (2008) BMJ 337 1840
Ogawa H et al (2008) Low-dose aspirin for primaryprevention of atherosclerotic events in patients with type 2 diabetes: a randomised controlled trial JAMA 300 2134-2141
National Collaborating Centre for Chronic Conditions (2008) Type 2 Diabetes: National Guidelines for Management in Primary and Secondary Care (update) Royal College of Physicians