Thanks for posting. Before anything else, you'll need to establish what variables you need to qualify an observation as a unique observation. It sounds like you are most the way there with patient ids, but you may need to go a bit further. For example, can one patient id appear for several dates in the same table? If so, date is probably needed to get at unique variables. Once you have that, I would recommend using a join function from dplyr (such as inner_join) to merge all of your data frames into one cohesive dataset, then use dplyr::select to look at the variables you want to look at.
If you want to look at some code for how to do that, please provide a REPRoducible EXample, instructions for which can be found here.