Baseline risk

Baseline risk, sometimes called the control event rate, is the probability of the outcome in the absence of the intervention. It anchors every other risk measure, because relative figures only become meaningful once you know what they are relative to. A person's baseline risk depends on age, sex, existing conditions, and other factors, so a trial's average may not match any individual reader. When reading a study, find the event rate in the control group and use it to translate relative results into absolute terms. For example, a drug that lowers relative risk by 30 percent removes 3 events per 100 people when baseline risk is 10 percent, but only 0.3 per 100 when baseline risk is 1 percent. Look for whether the study population's baseline risk resembles the group the results are being applied to; borrowed conclusions from high-risk trials often overstate benefit in lower-risk settings.