GAD Antibodies and C-Peptide Tests

Hello @Hollieo4 - it's not unusual after diagnosis to experience a period of well controlled Bg levels, so after the stress of diagnosis it can recover slightly with controlled insulin intake. Whether or not you want to ask for GAD test is something you need to ask your GP, but the phase will end at some point and your insulin requirements will increase in time, however as your body suffered DKA through a period of increased stress it does point to the fact that type 1 is the cause, so not sure what purpose having a further confirmation will give you. Personally I went through a period of denial and questioning after being diagnosed, thinking it couldn't happen to me and that somehow I could cheat the diagnosis, however coming to terms with it meant I was more accepting of it and able to deal more pragmatically with it.

Hollieo4 said:

I really want these tests just for my own peace of mind so that I never have to doubt my diagnosis.

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Sadly a GAD test may not give you that, because it's perfectly possible to be T1 but have a negative result on the GAD test.
"Presence of the GAD antibodies is observed in 75% of people with type 1 diabetes at diagnosis.
If the test shows GAD antibodies are present, this indicates that the patient has type 1 diabetes. If no GAD antibodies are present, however, the test cannot be conclusive in saying that the patient does not have type 1 diabetes."
http://www.diabetes.co.uk/gad-antibody-test.html
Geoff

librarising said:

Sadly a GAD test may not give you that, because it's perfectly possible to be T1 but have a negative result on the GAD test.
"Presence of the GAD antibodies is observed in 75% of people with type 1 diabetes at diagnosis.
If the test shows GAD antibodies are present, this indicates that the patient has type 1 diabetes. If no GAD antibodies are present, however, the test cannot be conclusive in saying that the patient does not have type 1 diabetes."
http://www.diabetes.co.uk/gad-antibody-test.html
Geoff

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I think Geoff is spot on with this. Not all type 1-s come back positive for GAD.

However.....ALL type 1-s have almost non-existing C-Peptide levels (as far as I know).

Even in the very beginning (where I didn't have to give myself basal because bolus was enough all day and throughout the night) I still came back with 'zero point something' for C-Peptide. At the time we still had hope that I may be Type 2 instead...

As for making insulin on your own: newer research says that we actually have more beta cells left than we thought, and they can last you a lifetime (for some type 1-s). Now the bad news: the remainder of beta cells still won't cut it because they're constantly attacked by antibodies. :***:

Hallo Hollie04,

As I mentioned in a PM, I had the c-peptide and antibody tests because of the strange presentation of my diabetes.

I found this helpful article when I was trying to interpret my c-peptide result: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3748788/

You may find the article gives you useful material to think with and to prepare questions for when you meet with the consultant. I don't think the tests can provide any certainty or guidance about how long you will honeymoon. But there are more types of diabetes under the sun than T1 and T2, and the precise identity of your diabetes would be worth knowing. One question you might want to pursue is, "I understand that MODY patients are commonly misdiagnosed as T1 but are more effectively treated with oral therapies rather than insulin. I know of at least one person who had gestational diabetes and was subsequently rediagnosed with MODY [she's also in the GDUK group]. Given my age (>30) and presentation, how can you rule out monogenic diabetes in my case?".

The honeymoon period confounds the issue, and so it may be that the consultant advises you to wait and see. You could then say, "Well there are risks to insulin therapy (hypos). Would it not be better to confirm the T1 diagnosis with c-peptide and antibody tests?"

I should add that I am new to this malarky--this is just my thoughts after reading the article. In my own case T1 was clearly indicated as I had c-peptide of 0.2 and GAD antibodies in the 7900s. Can't say it has brought me peace of mind though

Take care,
Hannahx

Hi. I had my c-peptide done privately by MediChecks as my GP wouldn't accept I might be T1. It showed I had insulin right at the bottom of the range. I also had a GAD done which was negative. As NICE says, having GAD test several years after diagnosis reduces it's reliability and there are other causes of beta cell death than antibodies.

Hi all, this is fascinating reading! I was diagnosed with T1D 2 months ago. GAD antibodies came back at 2000 & subsequent tests for 4 other beta cell attacking antibodies came back positive also (I had these as part of some research I've got involved in with address-2 for newly diagnosed T1Ds). I've also had c peptide tests and are currently at 1.17 so my pancreas is still functioning at the lower end of normal?!? Fingers crossed this strong honeymoon lasts but will be ready and watching for when it does diminish. Just got a Libre, amazing to see how low fat high carb foods spike my sugars but high fatty foods cause a very small rise in BG. It's almost as if a high fat diet would cause my overall HbA1c to be nice and low, although this diet wouldn't help with my addition to long distance running haha!
Any info on anyone's honeymoon duration would be interesting. I find usual when I ask for this kind of info I'm met with comments about not thinking about it and just accept it... For me I accept I have T1D and just want to enjoy hypo complication free runs for as long as I can and this honeymoon thingy is magic for that!

andybraith said:

Hi all, this is fascinating reading! I was diagnosed with T1D 2 months ago. GAD antibodies came back at 2000 & subsequent tests for 4 other beta cell attacking antibodies came back positive also (I had these as part of some research I've got involved in with address-2 for newly diagnosed T1Ds). I've also had c peptide tests and are currently at 1.17 so my pancreas is still functioning at the lower end of normal?!? Fingers crossed this strong honeymoon lasts but will be ready and watching for when it does diminish. Just got a Libre, amazing to see how low fat high carb foods spike my sugars but high fatty foods cause a very small rise in BG. It's almost as if a high fat diet would cause my overall HbA1c to be nice and low, although this diet wouldn't help with my addition to long distance running haha!
Any info on anyone's honeymoon duration would be interesting. I find usual when I ask for this kind of info I'm met with comments about not thinking about it and just accept it... For me I accept I have T1D and just want to enjoy hypo complication free runs for as long as I can and this honeymoon thingy is magic for that!

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The difference between high fat and low fat is probably related to fat slowing the emptying of food from the stomach to the small bowel. Carbohydrates are absorbed in the small bowel so if the food leaves the stomach more slowly then less insulin is required and a failing pancreas can cope.