It's Michigan State University that runs the tests for IAA, the same labs that do the IGF-1. It's a lot cheaper to do both tests at once. Greater than 20% IAA is considered positive. Most vets do dismiss it as unimportant, but most vets also don't do see a lot of home testing. The action of the antibodoes can change our dosing strategies. You need to be more aggressive with dosing, if positive for IAA, and similarly, you have to be very conservative if the IAA break. IAA is supposed to be self limiting after around a year and dosing needs can change dramatically when it happens.
Plus my vet talked about a consultation with the UofM to see if we wanted a CT scan and possible radiation therapy. Is that the same as SRT
Given Titan's IGF-1 number, I would save money and not do the CT scan, unless you were planning on following up with radiation therapy. Depends on what type of radiation equipment UofM has as to whether it's the same as SRT. There is conventional radiation therapy too, which is much harder on the cats. SRT can be completed in 2-4 days. The first day is a CT scan to confirm the tumour and map it for radiation purposes. The following 1-3 days are the radiation therapy. The SRT equipment is more expensive, which is why there are a limited number of locations that have it. But the corresponding good part about SRT is that they can be much more focussed on the tumour, and radiate very little tissue outside the tumour boundaries. Which means less side effects or damage to non tumour tissue. Which is why SRT is very good for brain tumours, which is what the benign pituitary essentially is. Note that radiation just neuters the tumour cells, it can still take up to two years to take full effect. Cyberknife is another option that possibly even better than SRT. But only available in a few places in the US for pets.
Other possible treatments for acromegaly, which your vet may or may not know about, is hypophysectomy (surgical removal of the pituitary) or some medical treatments (paseriotide and cabergoline). There are few places in the US that have experience with hypophysectomy for acromegaly, Washington State University and in LA. Ideally you don't want to be a vet surgeons first patient in this tricky surgery. The Royal Veterinary College in London are the most experienced and it is the gold standard (and most expensive) treatment option - most kitties are cured. The medical treatments are still being researched. Pasireotide (Signifor) is effective but very expensive - the long acting version Signifor LAR is best as it's just once a month injections. Cabergoline is in the research phase, again under the Royal Veterinary College, and a much cheaper option. Most kitties in the trial had their insulin needs greatly reduced, but so far only one, Marvin (on FDMB) has gone off of insulin.
Side note: looks like it's time for another increase with Titan.
. We are increasing his dosage every 6 cycles by .5 unit each shot. Initially we zoomed to 4 units 2x a day but thought bouncing or Symogyi might be in play. Went slowly back down to 1 unit 2x to see if a change and/or start over. Then did a IGF test. Positive at 255 o now with an AcroCat we are climbing the scale to see where we land. Thanks again for the link. He's already a 10,000 dollar puddy cat with his previous issues 
but he's ours!