GDA, ooppps, I meant GAD, but that will mean equally nothing to you
GAD = glutamic acid decarboxylase. A Type 1 and Type 1.5 will have these antibodies since they are related to your body attacking your pancreas. A Type 2 will general not have them.
My consultant is still trying to figure out what type of diabetic I am. They are pretty certain I'm not a Type 1 - so they are using that test to try figure if I'm a Type 2 or a Type 1.5.
I'm sure you know this, but just in case (and someone will probably have to correct the fine detail)...
Type 1 is where your body doesn't produce (much) insulin - generally found in young people (although as seen here it can be at any age)
Type 2 is where you body is resistant to insulin - generally found in older people
Type 1.5 / LADA - is a slow form of Type 1 where your body is slowly producing less and less insulin
MODY is Type 2 in young people
And yes I'll agree, a good GP will phone you if there is anything critically wrong.