Two steps lead to the diagnosis. The first is a blood test, chiefly tissue transglutaminase IgA (tTG-IgA), along with a total IgA level to check for deficiency. If it is positive, most adults need an upper endoscopy with small-bowel biopsies to settle the matter. The rule that matters most is to carry on eating gluten until every test is done, since cutting it out early can hide genuine disease.
According to Dr. Vipulroy Rathod, Gastroenterology Specialist in Mumbai, “Almost everyone who suspects celiac disease wants to start the diet that same day. Both tests depend on gluten being in the body. When it is removed, the antibodies fall and the lining of the small bowel begins to heal, so a genuine case can look normal. Test first, and change the diet afterwards.”
Which tests help confirm celiac disease?
What Tests Are Used for Celiac Disease Diagnosis?
- tTG-IgA blood test: This is the first test almost everyone gets. It picks up antibodies your body makes when gluten damages the gut lining, and it works best while you’re still eating gluten.
- Total IgA level: It’s ordered alongside tTG-IgA. A small number of people with celiac disease (around 3 in 100) are IgA deficient and can test falsely negative. In that case, IgG-based tests such as tTG-IgG or DGP are used instead.
- Upper GI endoscopy with duodenal biopsy: This is the confirming test in most adults. A thin scope goes through the mouth, and small samples are taken from the first part of the small intestine. See our overview of endoscopic services, and read what to ask before an endoscopy.
- HLA-DQ2/DQ8 gene test: This doesn’t diagnose celiac disease. A negative result, though, rules it out, so it’s useful when someone has already gone gluten-free or when results don’t add up.
What Happens During the Endoscopy and Biopsy?
- The procedure: You’re sedated, and the scope passes through your mouth into the duodenum. It’s a short procedure, and the doctor also checks your food pipe and stomach on the way.
- Why several samples: Celiac damage can be patchy, so guidelines recommend taking four or more biopsies. The pathologist then looks for flattened villi (the tiny finger-like folds that absorb food) and extra inflammatory cells.
- Afterwards: Most people go home the same day. Our guide to recovery after endoscopic procedures covers what to expect.
- If the scope isn’t enough: When symptoms continue or the picture is unclear, the small bowel may need a closer look. See capsule endoscopy and double balloon endoscopy.
What Determines the Right Diagnostic Approach?
- Whether you’re eating gluten now: Tests only work if gluten is in your diet. UK guidance suggests including it in more than one meal a day for at least six weeks before testing. Chapati, bread and biscuits all count.
- Your age: Adults usually need a biopsy. Some children with very high tTG-IgA levels and a second positive antibody test can be diagnosed without one, but only under a specialist’s guidance.
- Your antibody results: A high tTG-IgA gives a stronger case. A negative result with a normal total IgA makes celiac disease less likely, but not impossible if your symptoms strongly point to it.
- Your symptoms and history: Long-standing bloating, diarrhoea, weight loss or anaemia, or a close relative with celiac disease, all raise suspicion. Similar symptoms can come from other conditions, so see bloating after every meal and microscopic colitis.
Key Takeaways
- Celiac disease diagnosis starts with a tTG-IgA blood test plus a total IgA level.
- In most adults, an endoscopy with duodenal biopsies confirms it.
- Don’t stop eating gluten before testing is finished.
- A negative blood test doesn’t always close the case if your symptoms are strong.
- If you’re already gluten-free, a gluten challenge or a gene test may be needed.
Frequently Asked Questions
In adults, usually not. A positive blood test is normally confirmed with an endoscopy and biopsy. In some children with very high antibody levels, the biopsy can be skipped.
No. Stopping early can give false-negative results on both the blood test and the biopsy. Keep eating gluten normally until your doctor says the testing is complete.
Speak to your gastroenterologist. You may be asked to eat gluten again for a few weeks before repeat testing, or to have an HLA gene test, which isn’t affected by diet.
Not always. IgA deficiency or a low antibody level can hide it. If your symptoms still point to celiac disease, an endoscopy with biopsies may be advised.
Disclaimer: This blog is for educational and informational purposes only and should not be considered professional advice.
