| Not the antibody test, that was done but inconclusive.Only 70-80% of type 1s do test positive for GAD.To add to the complication there is a division between type 1a(autoimmune ) and type 1b (idiopathic) My Doctor(only last week) suggested that I could be either.
I think that the C peptide showed that I still was producing some insulin.
The main reason for a diagnosis of type 1.5 rather than type 2 with beta cell exhaustion was my history.I presented with high fasting BG and ketones but only needing relatively small amounts of insulin to lower it and get rid of the ketones. History of initial weight loss, three years off and on with diabetes symtoms followed by further rapid weight loss.
I've just gone on a pump 3 years after diagnosis, so I've had diabetes for at least 6 years. Its early days but at the moment my basal/bolus ratio is 40%:60% which according to John Walsh may be because I still have some insulin of my own at least 6 years after the first symptoms.
If you can get the antibody tests do so. They may confirm 1.5 but if negative it doesn't mean that type 1(1.5) of some sort is out of the question.  | 
