Understanding Celiac Blood Tests
So, to make a diagnosis of celiac disease, you need to have positive blood test results and positive small intestinal biopsies ON a gluten-containing diet.
The blood tests can be complicated, so I’ll try to make it simple.
As with a lot of things in medicine, the celiac blood tests have their own language. Your doctor may refer to the celiac blood tests as “serology”. Serology is another term for antibody, or immunoglobulin (Ig). The reason for this is because the celiac blood tests are, in fact, a measurement of specific antibodies or immunoglobulins produced in your blood stream upon exposure to gluten.
Are you still with me?
There are various classes of antibodies – the A class, M class, G class etc,. The celiac specific antibody is usually based on the ‘A’ class.
The most frequently tested celiac antibody is the immunoglobulin A-based tissue transglutaminase (commonly known as “tTG”). I know, it’s a mouth-full.
This antibody has been determined to be the single best test to help detect celiac disease. In addition to the tTG, another commonly tested antibody is the IgA/IgG-based deamidated gliadin peptide (commonly known as “DGP”). Since both antibody tests are based on the antibody A level, it is important that your doctor check your IgA level to make sure that is normal at baseline.
To summarize, if your doctor suspects celiac disease, they should check:
- IgA level in your blood
You may have heard of the IgA-based endomysial antibody (EMA). This is an older blood test that is sometimes used to confirm the results of the tTG. The anti-gliadin antibodies (commonly called AGA) are older, less accurate blood tests that are rarely used in common practice. The AGA blood test has been replaced by the DGP test.
There is no easy way to detect celiac disease in someone already on a gluten free diet.
For that reason, it is very important to consult with your doctor first before going gluten free.
The tTG and DGP antibody tests are useful tests to monitor if someone with celiac disease is following a gluten free diet. A drop in these antibodies every 3 months or so is a good indication that a patient is following and responding to a gluten free diet. Usually, this goes along with an improvement in symptoms, but not always. In those cases, other co-existent conditions need to be investigated.
Despite the accuracy of the blood tests, still, the best way to see how you are doing on a gluten free diet is evaluation by an experienced nutritionist. There really is no substitute for a heart-to-heart with your nutritionist. Feel free to express your concerns and fears, your frustrations and questions, and let your healthcare team do the best they can to help you stay healthy.