Is there a way for an at risk person to detect early changes (via blood tests etc) that usually precipitate development of non-hodgkins lymphoma?

Yes. Seeing your general doctor regulary for check-ups and physical exams is the best way. Sometimes you can see signs of lymphoma in a blood test, like a high LDH, but this is not an effective screening method. Only if your doctor suspects that you may have lymphoma should she order further testing.

Related Questions

My granddad has non hodgkins lymphoma and bruising on tongue and lip, also coughing up chunks of blood in plegm, are there all related?

Likely. Lymphoma and it's treatments (eg: chemotherapy) can affect blood counts and platelet counts, which may cause bruising and bleeding. Make sure that your grandfather's doctor is aware of these symptoms. Read more...
It is possible. He needs to be seen by a physician quickly to know why he is having these symptoms. This could be very dangerous (low blood and platelet counts, etc.). Read more...