If a patient is status post organ transplant and comes in to have bloodwork done every so many months to check their levels what diagnosis code would you use as the principal diagnosis? The patient is not having any problems and they come in stricly for bloodwork only. Would you use the aftercare code V58.44 as the principal diangois, or would you use the follow-up code V67.09 as the principal diagnosis. I have some confusion on this matter and would appreciate some input from some other coders. What do you guys think?