Ok, I just looked it up. As far as the GAD antibodies go:
GAD antibodies - Persons with LADA usually test positive for GAD antibodies, whereas in type 1 diabetes these antibodies are more commonly seen in adults rather than in children.[2][10] Latent autoimmune diabetes - Wikipedia, the free encyclopedia
It's all very complicated, and I don't pretend to get it, which is why I go for text-bites like the quote above. Oh, and apparently you can have GAD antibodies and never become diabetic.

Great.