Celiac Disease Screening Test: Purpose, Test Details & Results

Celiac disease is a common, yet often underdiagnosed, autoimmune disorder driven by a reaction to gluten. Early and accurate diagnosis is essential to prevent long-term complications and improve quality of life. In this article, we'll take a deep dive into the why, what, and how of celiac disease screening—exploring not only the rationale but also the science behind the tests and what the results truly mean.

Purpose of Celiac Disease Screening Test

Understanding why screening for celiac disease matters is the first step toward early diagnosis and better health outcomes. Celiac disease can present with a spectrum of symptoms—or even no symptoms at all—making it tricky to spot without targeted testing. Screening helps identify individuals who might otherwise go undiagnosed and at risk for complications.

Why Screen for Celiac Disease?

Celiac disease affects about 1% of the Western population, but rates of diagnosed cases are much lower—largely because many people show only mild, atypical, or no symptoms at all 1 3. Screening can uncover hidden cases, especially in high-risk groups such as those with a family history of celiac disease, type 1 diabetes, autoimmune thyroid disease, or certain genetic syndromes 3 5.

Who Should Be Screened?

• High-risk groups: These include first-degree relatives of people with celiac disease, individuals with autoimmune disorders, and those with unexplained iron deficiency anemia, osteoporosis, or infertility 3 5 9.
• Asymptomatic populations: Some studies suggest that the majority of undiagnosed cases are found in people without classic gastrointestinal symptoms, supporting targeted screening over mass population screening 1 3 4.

Health Benefits of Screening

Early detection allows for timely treatment—namely, the initiation of a gluten-free diet—which can:

• Prevent complications such as malnutrition, osteoporosis, growth delay in children, and increased risk of certain cancers 3 10.
• Improve health-related quality of life, especially in those who were symptomatic before diagnosis 10.
• Reduce long-term morbidity and mortality associated with untreated celiac disease 3 10.

Is Mass Screening Recommended?

While mass screening can identify asymptomatic cases and prevent potential complications, current evidence does not fully support mass screening in the general population due to uncertainties around cost-effectiveness and benefits for asymptomatic individuals 3 4. Instead, a targeted, case-finding approach in high-risk groups is often recommended 3 5.

Celiac Disease Screening Test Details

Celiac disease screening hinges on reliable, noninvasive blood tests that detect specific antibodies. By understanding the options, their accuracy, and their limitations, patients and healthcare providers can make informed decisions about the diagnostic process.

How Do Celiac Disease Screening Tests Work?

Most screening tests are serologic—they detect antibodies produced by the immune system in response to gluten exposure.

IgA Tissue Transglutaminase (tTG) Antibody

• Role: The preferred initial screening test for both adults and children.
• Accuracy: High sensitivity and specificity (>90% in most studies); best used in patients consuming a gluten-containing diet 4 5 6 7.
• Limitations: May yield false negatives in individuals with IgA deficiency 5 6.

IgA Endomysial Antibody (EMA)

• Role: Highly specific; often used as a confirmatory test after a positive tTG result.
• Accuracy: Sensitivity and specificity approach 100% in some studies, but slightly less sensitive than tTG in mild disease 2 4 7 9.

Total Serum IgA

• Purpose: Screens for IgA deficiency, a condition more common in people with celiac disease. If IgA deficiency is present, IgG-based tests are used instead 5 6.

Deamidated Gliadin Peptide (DGP) Antibodies

• Role: Can be useful in young children under two and those with known IgA deficiency.
• Limitations: Lower accuracy when used as an isolated screening test, especially in IgA-sufficient children 7 13.

HLA-DQ2/DQ8 Genetic Testing

• Role: Not a diagnostic test but a powerful tool to rule out celiac disease. Virtually all people with celiac disease have HLA-DQ2 or DQ8, but these markers are also common in the general population 9.
• Usefulness: Best in complex cases, such as when a patient is already on a gluten-free diet before testing, or when serology and biopsy results are inconclusive 5 9.

Small Bowel Biopsy

• Role: The gold standard for confirming diagnosis. Recommended after positive serology before starting a gluten-free diet 5 9.

Screening Process: Step-by-Step

1. Initial serologic testing: Begin with IgA tTG and total serum IgA.
2. If IgA deficiency detected: Use IgG-based tests (e.g., IgG DGP).
3. If serology positive: Refer to gastroenterology for small bowel biopsy to confirm diagnosis.
4. If diagnosis is uncertain: Consider HLA typing and additional testing 5 9.

Practical Considerations

• Serologic tests should be performed while the patient is consuming a gluten-containing diet. Starting a gluten-free diet before testing can lead to false negatives 5.
• Do not rely on symptoms alone; many individuals with celiac disease are asymptomatic or have atypical symptoms 1 3 5.

Celiac Disease Screening Test Results & Follow-Up

Receiving screening test results for celiac disease can be both relieving and overwhelming. Interpreting the results correctly and following up with the right steps are crucial to ensure an accurate diagnosis and optimal management.

Understanding Your Test Results

• Positive serology (tTG, EMA): Indicates a strong likelihood of celiac disease, especially if both are positive. However, a small bowel biopsy is still necessary to confirm the diagnosis before starting a gluten-free diet 5 6 9.
• Negative serology: Makes celiac disease unlikely, but does not completely rule it out, especially in people with IgA deficiency or if testing was done after starting a gluten-free diet 5 9.
• Positive DGP (with negative tTG): Rarely predicts celiac disease, especially in IgA-sufficient children. Additional testing or specialist referral is advised before making any dietary changes 13.
• HLA typing:
  • Positive results indicate genetic risk but do not confirm disease.
  • Negative results virtually exclude celiac disease, making further testing unnecessary in most cases 9.

Confirming the Diagnosis

Why is a Small Bowel Biopsy Needed?

Despite the high accuracy of serologic tests, a biopsy is considered the gold standard because:

• Some conditions can cause false-positive or inconclusive antibody results.
• Biopsy allows direct visualization of the intestinal lining to confirm characteristic damage 5 9.

When Might a Biopsy Not Be Needed?

Select pediatric guidelines allow for a diagnosis without biopsy in highly specific cases (very high tTG levels, positive EMA, appropriate symptoms), but this is not universally adopted 5 6.

Follow-Up After Diagnosis

Immediate Steps

• Start a gluten-free diet only after confirmation. Premature dietary changes can interfere with diagnosis and future monitoring 5.
• Referral to a dietitian: Essential to ensure nutritional adequacy and support adherence 5 12.

Ongoing Monitoring

• Regular follow-up: Annual check-ups to monitor dietary adherence, assess for nutritional deficiencies, and screen for associated autoimmune diseases 12.
• Antibody testing: Used to monitor response to the gluten-free diet, but not fully reliable for detecting ongoing intestinal damage 11.
• Repeat biopsy: Sometimes recommended if symptoms persist or serology remains positive despite a gluten-free diet 11 12.

Long-Term Outlook

• Symptom improvement: Most patients see significant health and quality-of-life improvements after diagnosis and treatment 10.
• Complication prevention: Early and accurate diagnosis helps prevent long-term complications such as osteoporosis, infertility, and certain cancers 3 10 12.

Conclusion

Celiac disease screening is a vital tool for uncovering this common but often hidden condition. Early and accurate diagnosis can transform lives and prevent serious complications. Here’s what we covered:

• Screening is essential for early detection, particularly in high-risk and asymptomatic individuals 1 3 4 5.
• IgA tTG antibody testing is the preferred first-line screening tool due to its high accuracy 4 5 6 7 9.
• Total IgA measurement is crucial to prevent false negatives in those with IgA deficiency 5 6.
• HLA-DQ2/DQ8 genetic testing is valuable for ruling out celiac disease, especially in complex cases 9.
• Small bowel biopsy remains the gold standard for confirmation before initiating a gluten-free diet 5 9.
• Ongoing follow-up is key to ensuring dietary adherence, monitoring health, and preventing complications 12.

By understanding the purpose, process, and implications of celiac disease screening tests, patients and healthcare providers can work together for timely, accurate diagnosis and lifelong health.