Absolute numbers are important in patient information – with examples from labor induction research

Background Research literature and patient information material often present relative and not absolute risk differences. We argue that absolute numbers should be used more in patient information contexts, because relative and absolute risks are interpreted differently by the recipient: Risk differences tend to seem greater when presented in relative terms (e.g. relative risks (RR) or odds ratios (OR)), compared to absolute risks (e.g. absolute risk reduction/increase (ARR/ARI)). Patient information material should present probabilities of outcomes in an understandable way to help patients to make appropriate decisions. However, since relative estimates do not take into account the background prevalence of an outcome, it may be difficult for patients to consider the size of the problem. The aim is to raise awareness of the communication of scientific evidence among researchers, clinicians and stakeholders. We illustrate how absolute numbers can be used to make scientific knowledge more comprehensible and discuss the implications of the choices we make regarding type of information when communicating risks. Method With examples from labor induction research, we will define ARR, ARI, and number-needed-to-treat (NNT), compare them to their corresponding relative estimates, and demonstrate why they are often interpreted differently, even though they are equally correct and based on identical data. Findings As an example, we found RR=1.90 for low pH (<7.10) after induction at 41+0-6 gestational weeks compared to expectant management. In relative terms, the interpretation is that the risk of low pH is increased by 90 %, while in absolute terms, the interpretation is that labor induction increases the number of children with low pH by 4 %. Conclusion As health professionals we should be aware that our choice of which risk measures to present works as a tool by which we can influence people’s decisions regarding a certain intervention or treatment.