C Peptide Test

Take a read of the following Anna:

http://www.diabetes.co.uk/c-peptide-test.html

Hi Anna

You're doing the right thing.
Type 2 diabetes needs more care from medical teams than it's getting. People should be taught from the start to regularly test their BGLs, etc. I spoke to a recently diagnosed type 2 today and they still get told to only test their BGLs twice a week... that is ridiculous and irresponsible.
I'm type 2 and I was also told I was insulin resistant.... I still have on my medical records that I have "metabolic syndrome". The thing is you get to a point where nothing is working and you need to know what your body is doing.
The C-peptide test will tell your doc just how much insulin your pancreas is producing and whether or not it's enough. If you don't produce enough insulin, they take you off oral meds and put you onto insulin... as they did with me. I got told that I no longer produce sufficient insulin so I now have to top it up for rest of my life.
Then of course if they also include the GAD test along with the C-peptide they can see whether or not you actually have LADA (type 1.5).... which is often misdiagnosed as type 2.

Wishing you the best. :thumbup:

As you already using insulin, a GAD test would be useless really as the insulin you'll taken is likely to effect the result.. But you don't need both the GAD and C-Peptide test to determine whether somebody is T2 or not...

Not sure how much a C-Peptide test costs, but 10 years ago the GAD cost £500 hence why it was restricted to consultant authorization only..

If you'll under the hospital consultant, the C-Peptide test is very useful, as not only will it be able to indicate whether you'll are T2 or T1.5 it will also give an indication to whether you insulin response phasing is out, and what sort of insulin resistance you have..

Armed with this information your team will be able to work out what medication/s would work best in bring your diabetes into better control..

Hey Jopar!

jopar said:

As you already using insulin, a GAD test would be useless really as the insulin you'll taken is likely to effect the result..

Click to expand...

I'm afraid I have to completely disagree with you here. The GAD test looks for the presence of GAD antibodies which are markers for an autoimmune type of diabetes i.e. Type 1 or 1.5. The use of injected insulin has no impact on this. It is usually used to diagnose Type 1 diabetes. It isn't especially reliable as sometimes the antibodies are present and sometimes they're not. A positive result indicates Type 1/1.5 and is usually seen as a diagnosis. A negative test does not rule out Type 1/1.5. The cost is around £160 incidentally.

The fasting insulin test is affected by injected insuliln as they cannot differentiate between injected and natural insulin. It can be used to check for the level of insulin in the body at a given time; high insulin/high BG = Type 2, low insulin/high BG = Type 1/1.5. (It's a bit more complicated than that, but it will do as a simple explanation). Because this test is affected by injected insulin, it is not suitable for those who already inject insulin. Insulin also stays in the body only a short time, so it is not easy to get an accurate result. Naturally produced insulin starts as two parts which split to produce an insulin molecule and a c-peptide molecule. Injected insulin has no c-peptide. Therefore, measuring the c-peptide level can indicate how much insulin is being produced without being affected by injected insulin. It also lasts longer in the body than insulin (5 times longer I think, but I haven't checked that so could be wrong), so is easier to measure than insulin. Hence it is used in preference to the fasting insulin test. I don't know how much it costs.

Taken together, the c-peptide and GAD tests are used to distinguish between autoimmune and metabolic types of diabetes.

Anna - I would accept the c-peptide test and wait for the results. If it comes back low you could be either a progressed Type 2 (i.e. progressed to the stage where your beta cells have been destroyed) or Type 1/1.5. At that point, ask for the GAD test to differentiate. If your c-peptide test comes back as high, you are Type 2 insulin resistant.

All the best

Smidge

Sorry but I disagree this was the reason why I didn't have a GAD test, I had been using insulin for too long, and it would likely alter the test, so be non-conclusive..

As explained to me by my consultant...

And I don't think he was lying to me, as this was after I warned him on my first visit that I would not entertain any Bull *cough* and yes I said about wasn't anti-bodies different when I asked and he explained why not!

I agree with Smidge on this one.... I have had both GAD and C-peptide tests done a couple of times.

When things were looking pear shaped for me in 2010.... my endo did both GAD and C-peptide to re-diagnose for me. I guess I could've continued wasting money on thowing pills down my throat, etc.... but thankfully the result of this test showed why pills were not working on me. I'm now on insulin as a result.

I think that if you're type 2... one thing I've learnt is that you need to make sure your medical team is treating your condition correctly. They simply can't do that properly if they haven't done the diagnostic tests. And these tests may be needed more than once in your lifetime with diabetes.... as it's considered to be progressive by medical professionals afterall. If they can monitor what stage cancer and other diseases are at.... that should include diabetes too.

Well even on the main page on this site it says... That insulin shouldn't be started before the test

www.diabetes.co.uk/gad-antibody-test.html

But also interestingly, GAD anti-bodies are found in Gestational diabetes, as well as Stiff Man Syndrome and several other medical condition...

Problem with initialising insulin treatment it can give the pancreas a rest and lower the anti-bodies destroying the cells, so give a false negative, which is something a lot of newly diagnosed diabetics find, that just after starting on insulin, that their insulin needs drastically reduce even stop for a while...

C-Peptide is a cheaper test, this is a screening type test to the GAD testing, so should be done first then perhaps if not enough information is gained then GAD testing to see if a clearer picture can be built..

Interesting our Triglycerides can also be used as an indicator of insulin resistance, if the ratio is higher than 4 then insulin resistance is present!

Hey Jopar

jopar said:

Well even on the main page on this site it says... That insulin shouldn't be started before the test

http://www.diabetes.co.uk/gad-antibody-test.html

But also interestingly, GAD anti-bodies are found in Gestational diabetes, as well as Stiff Man Syndrome and several other medical condition...

Click to expand...

I think they are saying the GAD test should be done before insulin is started so that the consultant can make sure he/she is treating the correct condition. Injected insulin has no impact on the outcome of a GAD test. I was on insulin at the time my test was done and it still came back positive. The consultant was perfectly happy to perform a GAD test on an insulin user.

You are correct that GAD antibodies can be a marker for a couple of other conditions, but if you are not pregnant it isn't going to be Gestational diabetes. If you are already diagnosed with diabetes, a positive GAD test almost always indicates an autoimmune form of diabetes rather than a different condition, so by a process of elimination, they usually regard a positive GAD test as a diagnosis for Type 1/1.5.

Smidge

+1 That's how I was re-diagnosed with LADA

This is why GAD testing should be done before insulin therapy
www.labtesthelp.com/test/Glutamic_Acid_ ... e_Antibody

jopar said:

This is why GAD testing should be done before insulin therapy
http://www.labtesthelp.com/test/Glutami ... e_Antibody

Click to expand...

Ah, I see where the confusion might be. We oversimplify what is commonly referred to as the 'GAD test'. When you have a GAD antibody test for the purpose of distinguishing between autoimmune and metabolic types of diabetes, you actually have 2 or 3 antibodies tested for. There are four that can be used:

ICA - islet cell antibodies
GADA - beta cell protein cell antibodies (non-specific)
IA2A - beta cell antigen antibodies (non-specific)
IAA - insulin antibodies (specific)

The first three tests are not affected by injected insulin. The fourth test is affected by injected insulin, so is not used for patients who are already injecting insulin. The first two antibodies are found in around 70/80% of newly-diagnosed Type1s. However, the first test is lab intensive so they sometimes don't use it. The third set of antibodies are found in about 60% of newl-diagnosed Type1s. The fourth set (although specific) is only found in around 50% of Type1 children, and rarely found at all in adults. Therefore they simply drop this test from the 'GAD test' in anyone already using insulin. The more of the above tests come back positive, the more definite they are with a Type 1 diagnosis. However, as tests 2 and 3 are non-specific, they can indicate other conditions, so the consultant has to use his/her experience and judgement to interpret the results. Overall, around 95% of Type 1s show at least one type of the above antibodies at diagnosis.

Smidge