I am working with a data that is I believe left truncated. I am looking at how Veterans with MPNs have a different timing of arterial thrombosis (AT) compared with Civilians with MPNs.
In the data some veterans and civilians have AT after being diagnosed with MPN, which is no problem. However, some of the veterans and civilians experienced AT before being diagnosed with MPN. We are only considering first AT. This could lead to immortal time bias.
From the nature of the question, it seems to me that patients become at risk when they are diagnosed with MPN. So patients who experience AT prior do not enter the risk group before they are diagnosed, however they can never experience first AT again.
Are the patients who experience AT first left truncated? I am planning on doing a log rank test for veterans and civilians, but should I remove these left truncated patients first?
Any guidance is appreciated!