Change of diagnosis.

So I've been battling a claim that went into HLR for about two years. It was denied and closed because there was not sufficient enough evidence to raise it from a 0%. As it turns out my Doctor told me I actually was misdiagnosed and diagnosed me with another medical condition. I have very relevant evidence now for this condition that I hope can get rated at 30%. In this case would I file a supplemental claim because of the misdiagnosed condition? Or do I now have to start back to square one all over again with a new claim.