I have survival data on patients, coming from a clinic's datawarehouse. I want to do a survival analysis. The timeframe starts on the day a patient gets a certain examination, and ends 730 days (two years) later.
The data comes in with timestamps.
patient | examination.date | date.of.death | date.of.last.contact | comment |
---|---|---|---|---|
A | 01.01.2000 | NA | 01.01.2010 | Alive |
B | 01.02.2000 | NA | 01.03.2000 | Lost to followup |
C | 01.03.2000 | 01.04.2000 | 01.04.2000 | Died during study |
D | 01.04.2000 | 01.04.2010 | 01.04.2010 | Died after study |
So far, I have transformed the data to have the length of actual survival times, and an event column.
patient | surv.time | event | comment |
---|---|---|---|
A | NA | FALSE | Alive |
B | NA | FALSE | Lost to followup |
C | 31 | TRUE | Died during study |
D | 3653 | FALSE | Died after study |
Surv seems to take no argument for a time of last contact, so I am quite certain that I should at least make a correction for patient B, who was lost to followup, and enter 28 there (the duration between examination and last contact). Patient C is also quite clear: died during the study, and the duration until death is entered.
But my question is about the other two patients:
- should I enter 730 (the study duration) for patients like A, who lived beyond the end of the study?
- should I enter 730 for patients like D, who died after the study timeframe? Note that I have already set the event column to FALSE for these cases.
I read some examples on how to use the survival package, but they used very simplified cases with already-prepared datasets.