Here is a link to an old journal article on this site. It appears that the “definitive” diagnostic criteria for CIDP have changed quite abit.
The wikipedia entry for CIDP is also interesting and gives some context:
This study demonstrates that neurologists should be able to identify/diagnose CIDP without the nerve biopsy.
Hope this helps. There are different schools of thought around biopsy, obviously – if your neuro is keen to use as a diagnostic tool then you have to decide whether you are prepared to go through it. I haven’t had one myself, so I can’t help on that score.