Negative day values for Survival Analysis

Question

[Bnf83]

Hi guys

I'm applying Survival Analysis to some data. For the first time I encountered negative values (negative days) relative to the clinical info "last contact days to".

Does anybody know the reason why days are reported as negative values? What does it mean -5 days?

Best

e.

[Devon Ryan]

I assume that the negative day values you're observing are in the raw data. In that case, you'll need to ask whomever coded the data originally to see what they mean by that. There's no a priori meaning to negative days.