A relative hazard and an absolute promise
A fictional randomized trial reports a progression-or-death hazard ratio of 0.65 with a confidence interval excluding one. For this exercise, assume that the proportional-hazards model is an appropriate summary. A trainee tells a patient that the drug guarantees a 35-percentage-point reduction in the chance of progression for every treated person. The report has not supplied the individual baseline risk or the event probability at the time point being discussed. It also has not established an overall-survival or quality-of-life advantage. The supervising clinician asks for a careful explanation of what the relative estimate does and does not show before a benefit-harm conversation.
1. What does the supplied estimate describe?
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Under the stated model it describes an estimated 35 percent lower hazard of the defined event, not a 35-percentage-point absolute risk reduction.
2. Which information is still needed?
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Actual event risks and time point, uncertainty, other outcomes, harms and population applicability are needed for an informed individual discussion.