Celiac disease test: symptoms, blood values and when to test

Thinking about a celiac disease test? Start here: celiac disease is a lifelong auto-immune reaction to gluten, and roughly 1 in 100 people have it. The first step is usually a blood test that looks at a specific antibody. Your symptoms need not be in your gut, and you can arrange such a test yourself.

What strikes me after reading a lot of results: people look for celiac disease in the wrong place. They expect severe gut complaints, while in adults fatigue or a low iron level is sometimes the only clue.

Below I lay out what celiac disease actually is, which symptoms may play a part, which blood values give insight, and what a sensible next step looks like. Read it as an overview, not a diagnosis.

What is celiac disease?

Celiac disease is an auto-immune condition in which your defences react to gluten, a protein in wheat, barley and rye. Over time that reaction damages the lining of your small intestine. It's not an allergy and not an ordinary intolerance, even if the complaints sometimes look alike.

Researchers found in 1997 that the enzyme tissue transglutaminase is the target of that immune reaction (Dieterich, 1997). That insight underpins the blood test used today.

According to Thuisarts.nl, celiac disease often goes unnoticed for a long time, because the complaints vary so much. If you want to understand the difference with a gluten intolerance, read our piece on the difference between gluten intolerance and celiac disease.

What are the symptoms of celiac disease?

Celiac disease can cause gut complaints, but far from always. In adults the signals are often vague: fatigue, anaemia, a low iron level or unexplained weight loss. It's that silent form that gets missed most, because no one thinks of the gut.

The classic complaints are stomach pain, bloating, diarrhoea or, instead, constipation. Skin rash, mouth ulcers and joint pain also occur.

Many adults mainly notice trouble outside their gut. Think of lasting fatigue, anaemia or shortfalls in iron, vitamin B12 and folate, because your gut absorbs nutrients less well (Halfdanarson, 2007).

Your skin, your joints and your bones can speak up too. An itchy skin rash, vague joint pain or early bone loss sometimes fit the picture. On their own these are vague signals that say little. Together they can still give a doctor reason to look further.

What makes it tricky: the same complaints also fit a busy life, stress or a shortfall without celiac disease. That's exactly why the pattern matters more than one single complaint.

Recognise yourself in this? Read on in celiac disease symptoms in adults. If you're mostly tired, our guide on causes of persistent fatigue helps line up the trails.

Which blood test shows celiac disease?

The first step is almost always a blood test. It looks at an antibody called anti-tTG of the IgA type, and at your total IgA at the same time. A raised anti-tTG can point to celiac disease, but a gut biopsy usually confirms the diagnosis (Ludvigsson, 2014).

Why that total IgA too? Because some people make little IgA. With such an IgA deficiency the anti-tTG test can read falsely negative, and then a different antibody type is needed.

The table below links a complaint or situation to the blood value that can help. Read it as a tool to prepare the talk with your GP, not as a result in itself.

If you want to know exactly what each value means, read which blood values indicate celiac disease. With your result, watch the laboratory's reference ranges, as they can differ per lab.

How reliable is the celiac disease blood test?

The anti-tTG test is a strong first step, but not an absolute result. In clear celiac disease the test is usually raised, while a normal result doesn't always rule the condition out. So a doctor often confirms a raised result with a gut biopsy.

There are a few situations where the test is less reliable. With an IgA deficiency the anti-tTG can read falsely negative, and if you already eat gluten-free, the antibodies may have fallen again.

A slightly raised value isn't proof either. The level of anti-tTG says something about the chance, but not everything. So a doctor weighs your result together with your complaints and your history.

If you're unsure about your result, discuss it with your GP. They can decide whether a repeat or additional test makes sense.

Important: keep eating gluten before the test

This often goes wrong. The blood test and any biopsy only read reliably if you keep eating gluten in the weeks beforehand. If you've already gone gluten-free, the antibodies can fall and the test sometimes reads falsely reassuring.

Picture someone who has avoided bread and pasta for a month because it feels better. That's exactly when the test can give a skewed picture.

If you doubt whether you're getting enough gluten, discuss it with your GP before testing. That way you avoid a result that says little.

What happens after the blood test?

A blood result is usually back within a few working days. If your anti-tTG is raised, the GP often refers you for a gut biopsy. A doctor then looks at a small piece of gut tissue through an endoscopy, and that confirms the diagnosis.

If your result is normal, but your complaints persist? Then a doctor can look at other causes, or repeat the blood test later on.

A normal result doesn't always rule celiac disease out completely, especially if you were already eating gluten-free. So discuss a doubtful result with your GP, so together you can decide whether looking further makes sense.

Who is more likely to get celiac disease?

Celiac disease is more common in certain groups. If you have a first-degree relative with celiac disease, the chance is higher, because the tendency is inherited. It's also seen more often alongside some other autoimmune conditions.

Think of people with type 1 diabetes or an autoimmune thyroid condition. Celiac disease is also more common in Down syndrome and Turner syndrome.

That doesn't mean you have to do anything straight away. It does explain why a doctor sometimes thinks of celiac disease sooner in these groups. Worldwide about 1 percent of people have celiac disease, and a large share don't know it yet (Singh, 2018).

Can you develop celiac disease later in life?

Yes, you can. Celiac disease is regularly found only after your forties or fifties, sometimes triggered by an infection, a pregnancy, surgery or prolonged stress (Vilppula, 2009). The predisposition was already there, but surfaced later.

In adults between 30 and 55 the trail is often missed. The complaints get blamed on being busy or getting older, while a blood value sometimes explains part of it.

Read more in late-onset celiac disease.

What does gluten do to your intestinal villi?

Your small intestine is full of villi, tiny folds that absorb nutrients. In celiac disease the immune reaction to gluten damages those villi, so they flatten. That explains why shortfalls and fatigue so often play a part.

The hopeful part: once gluten leaves your diet, the villi recover gradually in many people (Rubio-Tapia, 2010).

How that process works, read in intestinal villi and celiac disease.

Celiac disease, gluten intolerance or an allergy?

These three are often mixed up, while they differ. Celiac disease is auto-immune, a gluten allergy is an allergic reaction, and gluten sensitivity causes complaints without gut damage or antibodies. So the test and the approach differ.

For the details I point you to our piece on gluten intolerance or celiac disease. If you wonder whether it's a broader food intolerance, read food intolerance testing.

Living with celiac disease: eating without gluten

If you have celiac disease, a lifelong gluten-free diet is currently the only approach. That sounds strict, but many people notice within weeks that their complaints ease. The Voedingscentrum explains that gluten sits mostly in wheat, barley and rye, and so in lots of bread, pasta and biscuits.

Gluten also hides in products where you wouldn't expect it, such as sauces, soups and some spice mixes. Reading labels soon becomes a habit.

As your gut recovers, the absorption of iron and vitamins often improves too. Some people therefore have those values checked again after a while, together with their doctor.

Getting a celiac disease test yourself

You can also have a celiac blood test done without a referral. You choose a test yourself, get pricked at a collection point and receive your result digitally, with an assessment by a doctor. That gives you insight quickly, without a wait.

A celiac disease test usually measures the anti-tTG antibody and your total IgA. If you want a broader look, at iron and vitamins at the same time for instance, an extended health checkup fits.

Some people choose to test when complaints persist and are hard to place. Whether that fits you depends on your situation and your preferences.

When your result arrives digitally, take time to read it calmly. The explanation and the doctor's assessment help you put the numbers in perspective, especially when a value sits just outside the reference range.

Frequently asked questions about the celiac disease test

Can you confirm celiac disease with a home self-test? There are home tests that look at antibodies, but they give a first signal at most. A blood test with a doctor's assessment is more reliable, and the diagnosis is usually confirmed with a gut biopsy.

Do you need to fast for a celiac disease test? For the antibody test you usually don't need to fast. What matters is that you keep eating gluten as usual in the weeks beforehand.

How long before you have the result? A blood result is often back within a few working days. With an online test you get it digitally, with a doctor's explanation included.

Does celiac disease ever go away? No, celiac disease is lifelong. With a gluten-free diet the complaints and the gut damage can largely recover, though.

My experience: people who go to their GP with a concrete question have a better conversation. If your complaints persist or you doubt your result, discuss your values with your GP, so together you can decide whether further tests make sense.

Every blood test result includes a professional assessment from a BIG-registered doctor. For treatment decisions, discuss your results with your GP.

References

• Singh P, et al. Global prevalence of celiac disease: systematic review and meta-analysis. Clin Gastroenterol Hepatol. 2018. PMID 29551598.
• Dieterich W, et al. Identification of tissue transglutaminase as the autoantigen of celiac disease. Nat Med. 1997. PMID 9212111.
• Ludvigsson JF, et al. Diagnosis and management of adult coeliac disease: guidelines from the British Society of Gastroenterology. Gut. 2014. PMID 24917550.
• Thuisarts.nl. Ik heb coeliakie. Nederlands Huisartsen Genootschap (NHG).