I was recently diagnosed (38 yr old) with Bass at Bristol. They used a combination of forms (one I answered and one completed by my mum) and 2 appointments with an autism nurse and a psychologist. In the first appointment I was given a book with pictures and asked to tell the story, some toys to make a story around, pictures to identify expressions and other similar tasks. At the second appointment they asked lots of questions about my relationships with others, what I enjoy, work, what I find difficult. I was asked to wait in the waiting room while they discussed between themselves and they gave me a diagnosis then. They explained what criteria they used and I had the chance to ask questions and followed up with a detailed letter.