2a Critical Numbers - Survival Analysis Flashcards
What is survival analysis?
The analysis of tables showing the amount of time for death (event) to occur
What is the event in survival analysis?
Death
What is survival time in survival analysis?
Outcome of interest to the event occurring
What are the different features on a survival analysis diagram?
1) Red X: Represents death of participant
2) Circle: Represents censored individual
- If don’t cross final line then either died before end or have left the study before the end depending on symbol
Define censoring
When a person leaves study either through reason not related to event or surviving until the end of the study
What are the 3 different types of censoring?
1) Person survives until the end of the study
2) Person leaves study midway through e.g. moves away or dies from another cause
3) Person excluded as they experienced event (death) before study commenced
What do Kaplan-Meier graphs show?
Two different survival groups being compared, starting at 1.0 as all are alive
- Line at 0.5 to highlight median
- Time on X axis
- Vertical lines to trend show when individual censored
What is the shading around each line on a Kaplan-Meier graph?
Confidence Interval
What is the log rank test?
Basic statistical test which tests the hypothesis that there is no significant difference between the survival curves of two or more groups over the study time
How does Cox regression work?
Regression tool to model the time to event accounting for censored data, whilst building in confounders
What is a special ability of cox regression?
Able to include multiple predictors to take into account background factors.
What is the risk of the event presumed to do in Cox regression?
Stay the same
What are the main interpretations of a Hazard Ratio?
> 1 means increase in hazard/risk
<1 means decrease in hazard/risk
e.g. HR of 2 means a 2 fold increase in risk
