The term “informed consent” implies that patients need to be aware of any possible benefits, risks and complications before agreeing to commence with a treatment. Most patients don’t have a medical or scientific background, so it is not practical for them to be fully informed of every aspect of the treatment; however, with respect to preventative treatments, it is important that patients are aware of just how likely they are to benefit.
Preventative medication is available for a wide range of conditions, most notably cardiovascular diseases, which may be prevented with beta-blockers, statins, aspirin, ACE inhibitors, diuretics and so on.
Let’s take statins – or ‘HMG CoA reductase inhibitors’ – which lower blood cholesterol levels by inhibiting cholesterol production in the liver and increasing the liver’s ability to remove cholesterol from the blood:
Statins are widely prescribed*1. Presently, NICE advises statins be prescribed for patients either with pre-existing cardiovascular disease (CVD), or with a >20% estimated 10 year risk of developing CVD . Their guidelines also state that:
“The decision whether to initiate statin therapy should be made after an informed discussion between the responsible clinician and the individual about the risks and benefits of statin treatment, and taking into account additional factors such as comorbidities and life expectancy.”
This is where I get uneasy. Yes, statins have been show to be beneficial using a number of different measures, but how the extent of their benefit is presented to the patient (if at all) is what concerns me.
To keep things simple, I’m going to use the statistics presented in the NICE guidelines in the document entitled “Statins for the prevention of cardiovascular events”. (They rather conveniently conducted a meta-analysis of all studies which had data in a “usable form”.)  The data shows that there is a significant reduction in deaths from cardiovascular disease in patients taking statins. The relative risk given was 0.79, meaning that the death rate from cardiovascular disease is 21% lower in the statin-treated groups than the control groups.*2
Let’s say then, that a patient presents to a physician with an estimated 20% risk of having a cardiovascular-related death in the next 10 years, and that physician believes it is in the best interests of the patient to prescribe statins. Those statins will reduce the risk of cardiovascular death by 21% (the relative risk reduction), to 15.8%.
This means that there is only a 4.2% chance that the patient will benefit from the drug if he takes it for 10 years (the absolute risk reduction) – 80% of the time he wouldn’t have died of cardiovascular disease anyway, and 15.8% of the time, he will die of cardiovascular disease regardless. That means he will take 3,650 tablets, with almost a 96% chance they will have no effect.
For many patients, the side effects and inconvenience associated with taking a regular medication may not outweigh the 4.2% chance that they will benefit – statins are not free of adverse effects and can be expensive. Yet many patients (and indeed doctors) may not be aware of just how small the chance of benefit is: perhaps if they did know, they’d be less likely to adhere to their medication (if they agreed to commence treatment at all).
Consider each of the following three statements:
● “This drug will reduce your risk of a heart attack by 21%.”
● “There is a 96% chance you will not benefit from taking this drug.”
● If 24 people take this drug, only one will benefit from the treatment
All paint very different pictures, but it is of great importance that all of these (and arguably others) be presented to the patient if they are to make a fully informed decision on a particular treatment. The third statement is based on the Number Needed to Treat, the inverse of absolute risk reduction. It is a figure which describes the number of patients who need to be treated to prevent one additional bad outcome, in this case a cardiovascular death. This is a particularly useful measure when discussing risks with patients, since it does not require an understanding of percentages to effectively convey its meaning.
However, while patients have a right to be fully aware about the possible benefits of any treatment they are on, we cannot ignore the economic argument – while a particular preventative treatment may only have a very small chance of benefiting the individual taking it, on a population-wide scale where large numbers of people are prescribed the drug, this may lead to a significant reduction in morbidity and mortality. In terms of life-years and the cost required to save them, preventative treatments are much more cost effective than so-called “rescue treatments” such as surgery or dialysis. This fact is of particular importance in healthcare systems with finite resources such as the NHS.
For medicine as a whole, it makes sense for people to take long-term preventive medicines that have benefit based in evidence. The overall reduction in mortality is cost effective for healthcare systems, much more so than waiting until a patient needs more expensive interventions such as surgery. However, at all times, doctors must respect the autonomy of a patient and should present the more realistic absolute risk reductions or numbers needed to treat when informing the patient about the efficacy of any treatments, even if this means fewer patients agreeing to take such medications.
 Tony Hope, Medical Ethics: A Very Short Introduction, OUP, 2004
*1 In the 12 months to March 2007, 41.03 million statin items were prescribed and dispensed in the UK at a cost of £550 million , about 0.7% of the NHS’s total budget for the same year. NICE estimates the number of patients taking statins regularly to be around 4.2 million (12 months to March 2007). Another report found 13% of those over the age of 30 had received at least one prescription of statins in the 12 months leading up to October 2006.
*2 I ought to point out here that all-cause death rates are also of crucial importance, since they take into account any side effects of the drug which may also increase mortality – there’s no point having a drug which reduces fatal MIs if it going to increase deaths from other causes. Statins have been shown to reduce the risk of disease from any cause by 17%.