I wish I had the answer...
DS1 (now almost 9) was diagnised with ASD 18 months ago. When we started the referral process a year before the assessment, I was convinced it was inattentive ADHD that would be the diagnosis, based on how he was/is at school. Classic appearance of day dreaming, inability to focus, needing to be "brought back" (three separate teachers told me this was their experience of DS), absence of any organisational skill, hyperfocus to the max on his own stuff but impossible to get interested in anything else, appalling short-term memory (but excellent long term). His teacher's completion of the Conors form said it all (I was astounded, she really got him to a tee).
But the psychologist who diagnosed said ASD - and I don't question that based on what came out in the assessment, stuff about his babyhood/toddler years and development, which I'd always known was "off", and particularly after having DS2, who is NT - the differences were subtle but also screamingly obvious in retrospect. I thought I was a bad mum who didn't connect well...
I queried the ADHD symptoms (as DS has a first cousin who has both ASD and ADHD, much more severely than DS) and he said he considered it all part and parcel of his ASD but that the acid test would be if he responded to medication. I'm leaning heavily towards pursuing this now, a trial, in any case, as behaviourally things are getting challenging, to put it mildly. He's definitely very impulsive.
But I don't know how to get a rereferral, or if that's even necessary. The psych we saw was a diagnostic clinic only, no follow up and we were left with basically that, no follow up, guidance, ideas of where to go next.
GP is involved again because of violence issues, Camhs bats a referral right back at him, school is thankfully having the EP see him in Sept. I'm hoping something will come of that... at least it'll be documented how he cannot focus in the classroom UNLESS he is really really engaged off his own bat on whatever it is. If he is - bingo.