A Simple Guide for Patients and Families
Celiac disease is an autoimmune condition triggered by gluten—a protein found in wheat, rye, and barley. For people with celiac disease, eating gluten causes the immune system to damage the lining of the small intestine. If left untreated, it can lead to malnutrition, chronic diarrhea, fatigue, anemia, and more.
So how is celiac disease diagnosed in the U.S.? Here’s a step-by-step overview in plain language.
1. When Will a Doctor Recommend Testing?
Doctors may suspect celiac disease and suggest testing if someone has:
- Chronic diarrhea, bloating, constipation, or unexplained weight loss
- Fatigue or iron-deficiency anemia
- Type 1 diabetes, thyroid disease, or other autoimmune conditions
- A family history of celiac disease
- Growth problems or developmental delays in children
2. Step One: Blood Tests (Antibody Screening)
The first recommended test is a simple blood test to look for specific antibodies related to celiac disease.
The most common tests include:
- tTG-IgA antibody – the most accurate and sensitive first test
- Total IgA level – to rule out IgA deficiency (which can cause false results)
- DGP (deamidated gliadin peptide) IgG antibody – used if IgA levels are low
🔺 Important: These tests must be done while you are still eating gluten. A gluten-free diet before testing can cause false negatives.
3. Step Two: Small Intestine Biopsy (Endoscopy)
If antibody results are positive, doctors typically recommend an upper endoscopy to take small tissue samples from the small intestine (usually the duodenum).
If the biopsy shows damage to the intestinal lining (such as shortened or flattened villi), it confirms a diagnosis of celiac disease.
📌 Why is a biopsy important?
- It confirms the diagnosis
- Shows the level of damage
- Helps track healing after starting a gluten-free diet
4. Are There Exceptions to the Biopsy?
Yes, in certain cases a biopsy may be skipped:
- Young children with very high antibody levels (10× the normal limit) and typical symptoms may be diagnosed without a biopsy
- People with dermatitis herpetiformis (a skin form of celiac) can be diagnosed via a skin biopsy
- In patients unable to undergo endoscopy for medical reasons, doctors may rely on blood tests and symptoms
Still, most adults and children are advised to have a biopsy for accurate diagnosis.
5. Is Genetic Testing Necessary?
Celiac disease is strongly linked to two specific genes: HLA-DQ2 and HLA-DQ8.
- About 97% of people with celiac have one of these genes
- If neither gene is present, celiac disease can almost certainly be ruled out
- Genetic tests are useful when:
- Blood and biopsy results are unclear
- The patient is already on a gluten-free diet
- Screening family members for risk
Summary
The standard U.S. diagnostic process for celiac disease typically includes:
- Blood antibody tests
- If positive → Small intestine biopsy
- In special cases → Genetic testing or biopsy may be skipped
If you or your loved one has symptoms or risk factors, talk to a doctor about getting tested. Early diagnosis and a lifelong gluten-free diet are key to preventing complications and improving quality of life.
References:
Mayo Clinic Laboratories
CHOKKALLA, Anil K., et al. Path Towards Biopsy-Free Diagnosis of Celiac Disease in Pediatric Patients. Clinica Chimica Acta, 2024, 557: 117891.
PARRINELLO, Giuseppe, et al. Diagnostic accuracy of a novel point‐of‐care test for simultaneous detection of anti‐transglutaminase IgA and anti‐deamidated gliadin IgG antibodies. Journal of Clinical Laboratory Analysis, 2024, 38.3: e25003.
