Is consent ever informed if the numbers that describe risk remain a mystery to most people? Better ways and numbers1 to explain overall benefits and risks like numbers needed to benefit (NNB) and numbers needed to damage (NND) are welcome, but may fail to inform most decisions. Doctors often don’t know the numbers needed to treat (NNT) and numbers needed to harm (NNH) or don’t explain the true benefits and harms of tests and treatments. Patients usually consent with only a poor understanding of their risks.
Patients usually overestimate the benefit of treatments.2 For example, many people using statins or antihypertensive’s believe they are substantially reducing their risk of heart attack or stroke. Assuming that the treatment is safe and used for 5 years, only a few patients would take a drug if they thought that they had a 5% chance or less of benefiting (NNT 20). Half of the patients would take a drug if the chance of them benefiting was 20% (NNT 5). If the benefit was 5% or less then the number of patients willing to take a preventive drug was doubled if their doctor recommended the treatment. Most interventions are not that good.
Different doctors and patients cope with the same risk differently and the subsequent management of the same conditions varies widely.3
How can understanding of risk and consent become better informed?
GPs need to know and explain the frequency of benefits and harms of the tests and treatments that they recommend to patients. To be able to do this risk scores like NNT, NNH, NNB, NND for tests and treatments need to be easily accessible to inform everyday decision making and GPs need to benchmark their own understanding and tolerance of risk and make this clear when they make recommendations to patients.
If patients can make sense of their risk they will make more informed and personal choices about their care (and may often decline care).
- © British Journal of General Practice 2013