Primary healthcare news, information & resources


What we've been reading - December


Keeping up with medicine is made easier when we share clinical stories with our colleagues. On this page we share brief learnings and articles that have interested our GP liaison team during the month of December. If you come across an article, video or resource you think clinical and management teams should know about, send it to newsletters@pinnacle.health.nz.

Cardiovascular Disease and asprin use - thoughts from Dr Jo Scott-Jones

The 2018 Cardiovascular Disease (CVD) guideline says that the risks of taking aspirin outweigh the benefits for patients with a >15 per cent CVD risk over 70 years of age, and this has caused some GPs to question whether or not to stop aspirin in these patients even if they have established cardio or cerebro-vascular disease.

The short answer is NO!  

Aspirin is recommended for secondary prevention CVD for all ages.

What about the advice for primary prevention?

The new guideline says the following of Aspirin.

  • In patients under 70 years with a five-year CVD risk of 15 percent or greater the benefits of aspirin may outweigh the bleeding risk and should be considered. Potential benefit (reduction in non-fatal MI and possible small net years gained) and bleeding risk must be carefully assessed and discussed during shared decision-making.
  • In patients aged over 70 years with a five-year CVD risk of 15 percent or more the balance of benefits and harms cannot be determined with aspirin and use is not recommended for primary CVD prevention.
  • In patients with a five-year CVD risk of less than 15 percent, aspirin for primary prevention of CVD alone is not recommended.


What about patient choice and shared decision making?

The guideline suggests avoiding using aspirin for patients over 70 for primary prevention based on a value judgement that an approximate 25 per cent improvement in the 15 per cent 5-year risk of a CV event by taking aspirin is not worth the doubled increased relative risk of bleeding.

How do you explain this to patients?

The best way I have found of visualising CVD risks and benefits is using an online calculator from James McCormack which uses a 100 person "happy face" chart and he has adapted it so it can be based on the NZ PREDICT data combining this with the risks and benefits of various interventions.

Using this tool to give a 70 year old woman a 15 per cent 5-year risk of CVD she needs to be a smoker, have a systolic BP of 166, a total cholesterol of 6.4 and an HDL of 0.8 if she is living in an area of low deprivation and has no other associated risk factors.

When she starts aspirin her 5-year risk drops by  1.5 per cent - a numbered need to treat (NNT) of 67 over 5 years.

To have the same risk as a man, the same parameters apply except he is a non-smoker, and starting aspirin gives a 2.3 per cent reduction in risk (a NNT of 44 over 5 years.)

What about the risks of harm from aspirin?

James McCormack has this as a number needed to harm (NNH) of 200 yearly for a major bleed. But we know the baseline risk of GI bleeding changes with age and gender and the baseline risk also changes when symptoms are present, or when people use NSAIDs.

The antithrombotic trialist secretariat indicate the baseline incidence rate for an asymptomatic person aged 70-79 is estimated to be 1.8 (women) 3.6 (men) and over 80 years to be 3.0 (women) and 6.0 (men).

If the baseline risk is doubled by aspirin use to between 3.6 and 12 depending on age and gender, this gives a NNH of between 500 for women and 166 for men.

This makes me think that for women aged 70 with a 15 per cent 5-year risk primary prevention with aspirin may be an easier choice than it is for men as she has a NNT of 67 which is not so good but OK, but a NNH of 500 which is pretty good. For a man with a NNT of 44 and a NNH of 166 it's still an option that many would take.

In support of using aspirin in secondary prevention for whatever age in the guideline (table 5 page 11) says where established CVD is present there is strong evidence for medication including anti-platelets for secondary prevention.

This is reiterated clearly in the BPAC interpretation of the new guideline.

Further evidence is cited in DynaMed Plus (which you can access for free by going to DynaMed Plus, choosing institutional login - username: midlandsdmp password: midlands.)  

The last major review of the evidence I can find is from January 2002 (Papers Collaborative meta-analysis of randomised trials of antiplatelet therapy for prevention of death, myocardial infarction, and stroke in high risk patients) but there continue to be trials involving aspirin for secondary prevention mostly in "polypills" or using a ppi to reduce potential bleeding - no recent papers I have found are questioning the value of aspirin in secondary prevention.

From the above paper

"Benefits exceed hazards in most high risk patients.

Our results suggest that among individuals at high risk of occlusive vascular disease, the proportional risk reductions with antiplatelet therapy are roughly similar in most categories of patient (although they are smaller in acute stroke). Consequently, a patient's absolute risk is likely to be more important than the proportional reduction in serious vascular events in determining the likely benefit of antiplatelet therapy. In patients at particularly high risk of vascular events, the benefits of antiplatelet therapy are large. For example, among 1000 patients with acute myocardial infarction who are given one month of aspirin and then continue to take low dose aspirin for some years, about 40 would avoid a serious vascular event during the first month and about a further 40 would avoid a vascular event in the next couple of years. Similar sized long term benefits are likely to be seen if antiplatelet therapy is started soon after stroke or transient ischaemic attack and continued long term. Even in patient populations at intermediate risk (2-3% a year of serious occlusive vascular events) such as some patients with no previous vascular event but with stable angina, atrial fibrillation, or peripheral arterial disease, antiplatelet therapy for a couple of years would be expected to prevent about 10-15 vascular events for every 1000 patients treated.

The present evidence suggests that the proportional increase in the risk of major bleeding of about one half is similar among a wide range of categories of patient. Population based observational studies have found that regular use of aspirin (at a dose of ≤300 mg/day) is associated with around a twofold increased risk of upper gastrointestinal bleeding (or perforation).57 It therefore seems likely that the benefits of antiplatelet therapy will far outweigh any hazards unless the absolute risk of bleeding is high (such as among haemodialysis patients) or the absolute risk of a vascular event is low (as in apparently healthy people). Consequently, unless some definite contraindication exists, antiplatelet therapy should be considered routinely for all patients whose medical history implies a significant risk of occlusive vascular disease over the next few months or years, and it should generally be continued for as long as the risk remains high."

I know this is from 2002 but I won't be stopping prescribing aspirin in patients of any age with established CVD unless there is a compelling reason to avoid it (or my patient refuses!) and I may well co-prescribe a PPI especially for patients over 75 years as suggested by Rothwell and colleagues recently.

I hope this helps reduce any confusion, or maybe it adds to it?  

Meningitis W and advice to patients - thoughts from Dr Jo Scott Jones

Has anyone else been asked by parents if their child should be vaccinated against Meningitis W? The press coverage has caused great concern, which is understandable. The Immunisation Advisory Center (IMAC) provides unequivocal advice mengincoccal vaccine should be offered to: "Other infants and young children aged under five years, adolescents and young adults. Particularly adolescents and young adults living in close proximity to each other (eg. boarding school, university halls of residence or in long-term institutional care)." 

They indicate that Meningitis B is the most likely organism and needs Bexsero (at a cost of $96.50 plus, each, and at least two doses) where the other strains ( A,C,Y, and W ) can be covered with one of a choice of two vaccines Nimenrix or Menactra which again can be purchased at a cost of $80-90 plus. 

What are you going to say to a parent who asks if they should vaccinate their three month old? Will it change if they are dep 9/10 and Māori?

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Mengincoccal disease information for health professionals: read the latest information from the Immunisation Advisory Centre (IMAC).

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