Use absolute risk rather than relative risk

information prescriptions groupFor example, the risk of an event increases from 1 in 100 to 2 in 100, rather than the risk of the event doubles.

On occasion, it may be justifiable to include relative risk, for example in certain screening tests when relative risk may be more effective at encouraging uptake. However, absolute risk should always be included in addition to relative risk.

‘Number needed to treat’ is sometimes used to convey probabilities and risk but several studies suggest that this format is poorly understood by patients and may increase the perceived effect of treatment (for example BMC Medical Informatics and Decision Making, 13(Suppl 2)).

Why is this important?

For communicating risk reductions, relative risk reduction (RRR), compared with absolute risk reduction (ARR) and number needed to treat (NNT), may be perceived to be larger and is more likely to be persuasive. However, it is uncertain whether presenting RRR is likely to help people make decisions most consistent with their own values and, in fact, it could lead to misinterpretation.

Akl EA, Oxman AD, Herrin J, et al., Using alternative statistical formats for presenting risks and risk reductions. (2011.) Issue 3. Art. No.: CD006776. DOI: 10.1002/14651858.CD006776.pub2.. Cochrane Database of Systematic Reviews.
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