I have been given this diagnosis and feel a bit confused as I have not had many tests to confirm it. For those who have AN, what tests did you have and who diagnosed you?

I am under the care of a gastroenterologist who specialises in gastroparesis and a rheumatologist. They both feel that I have AN, secondary to rheumatoid arthritis (which I've had since 2009). I had a gastric emptying study which showed very delayed gastric emptying. I also had a test which recorded nerve signals to the stomach. This showed that the actual muscle is healthy but the nerve has been damaged and is sending inappropriate signals to the stomach. I have an abnormal heartbeat and an echocardiogram was normal. All this has led them to conclude the diagnosis. Reading online has made me discover that people are usually diagnosed by a neurologist. Should I be asking for this or is my diagnosis pretty conclusive?

Thanks in advance. I freely admit that this area is not my forte, so would appreciate any information.