I am doing a survival analysis in R with the
I think I am working with left-truncated data, but I'm not entirely sure how to handle it.
I have a cohort of patients diagnosed between 1990 and 2012. All the patients have a well-defined time of diagnosis (entry time). However, the outcome of interest (specific worsening of disease) has only been documented from the year 2000 and onwards. For patients diagnosed before 2000, it is therefore not known whether the outcome has occurred before that time - only after.
My first thought was that I needed to restrict the analysis to the time period from 2000, only including patients diagnosed after that point in time. After doing some reading, it appears to be unnecessary to exclude patients diagnosed before 2000. This seems to be left-truncation and that can be dealt with in
Surv(time1, time2, event), where time1 is left-truncation time (time from diagnosis to the start of documentation of the outcome) and time 2 is the time-to-event (from time of diagnosis).
Here are two examples of patients in my dataset:
Patient #1: Diagnosed in 1999. Outcome observed in 2001. Left-truncation time: 1 year (to 2000). Time-to-event: 2 years.
Patient #2: Diagnosed in 2001. Outcome observed in 2005. Left-truncation time: 0 years. Time-to-event: 4 years.
For these patients, I suppose their survival times (in years) in the survival object would be (respectively):
Surv(time1 = c(1,0), time2 = c(2,4), event = c(1,1))
Is this an example of left-truncated data? If so, is this the correct way to handle it?