mumof3,
If you live in the UK or not- the Liza Jane spreadsheets list all the tests for every possible form of PN. These tests are available universally. and if some places are not equipped to do them, Johns Hopkins has a mail-in kit for the skin punch biopsy that any GP can follow instructions on how to obtain the samples and send then off.
These spreadsheets were designed for PN'ers by PN'ers and medical professionals.
Use them, they're free.