This topic is covered by the LITFL entry, Hazard Ratio, Median Ratio and Kaplan-Meier Curves. It refers to curves of events over time, eg. survival over time.
- Hazard rate = rate at which an event happens over time
- Hazard ratio = treatment hazard rate / control hazard rate
- Interpreted along a measure of time, eg. over 1 year
- "odds of winning the race" - not the margin of victory
- HR of 1 = equal event rate between treatment and control groups
- HR of 2 = twice the number of patients will have the event in the active treatment group
- HR of 0.5 = half the number of patients will have the event in the active treatment group
- "the margin of victory" - not odds of winning the race.
- Median time = time at which 50% of cases "win the race"
- Contrast with Mean time which is the average resolution rate for that group
- This measures how much faster the treatment achieves an outcome when compared to placebo)
- Median ratio = placebo median time / treatment median time
- Length of time from study entry to disease end-point
- Compares treatment group and control group
- Median time and mean time are derived from these curves