Celiac Disease Panel (Anti-tTG IgA & Total Serum IgA)
Also known as: Tissue Transglutaminase IgA, Anti-tTG Test, Celiac Serology, Gluten Sensitivity Blood Test, IgA Anti-tTG
Parameters Measured in the Report
A breakdown of individual biomarkers and biological reference intervals typically found in your report:
| Biomarker | Standard Range | Unit | What It Means |
|---|---|---|---|
Anti-tTG IgA (Tissue Transglutaminase) (tTG-IgA) | Negative: < 10.0 Weak Positive: 10.0–15.0 Strongly Positive: > 15.0–100+ (High Titer: ≥ 10x ULN) | U/mL (or CU) | Primary screening autoantibody; >95% sensitive and specific for celiac duodenal villous atrophy. |
Total Serum IgA (Quantitative IgA) | Adults: 70–400 | mg/dL | Evaluates baseline IgA; identifies Selective IgA Deficiency (which causes false-negative tTG-IgA). |
Deamidated Gliadin Peptide (DGP IgG) (DGP-IgG) | Negative: < 20.0 | U/mL | Secondary celiac biomarker used when Total Serum IgA is deficient, or in young children under 2 years old. |
* Note: Reference ranges may vary slightly between testing instruments and reagent kits. Always refer to the reference interval printed on your specific pathology report.
Clinical Focus
High-affinity IgA autoantibodies directed against tissue transglutaminase (tTG) enzyme in intestinal mucosa, standardized against Total Serum IgA.
Sample & Specimen
Venous blood (Serum tube)
Fasting Protocol
Must be on a regular daily gluten-containing diet (wheat, barley, rye) for 6–8 weeks before testing. Do NOT start a gluten-free diet before testing.
Turnaround Time
12–24 hours
What Is This Test?
Why Did Your Doctor Order This Test?
Physicians routinely prescribe the Celiac Screen (tTG-IgA) in the following clinical scenarios:
How to Prepare Before Your Test
- CRITICAL: You MUST be eating a regular gluten-containing diet (at least 1 to 2 slices of wheat bread or equivalent daily) for 6 to 8 weeks prior to testing.
- If you eliminate gluten before the blood test, autoantibody levels will clear from your bloodstream, leading to a FALSE-NEGATIVE test result.
Understanding Your Results
What higher or lower readings generally mean in clinical practice:
If Values Are Higher Than Normal
A strongly positive Anti-tTG IgA (>10x upper limit of normal, ≥100 U/mL) accompanied by positive Endomysial Antibodies (EMA) is virtually 100% predictive of Celiac Disease. In children and adults, high titers guide confirmatory upper endoscopy with duodenal biopsy to verify Marsh Grade 3 villous atrophy.
If Values Are Lower Than Normal
A negative Anti-tTG IgA in an individual with normal Total Serum IgA who is consuming gluten virtually rules out Celiac Disease (>98% negative predictive value), suggesting that digestive distress may be Non-Celiac Gluten Sensitivity, wheat allergy, or Irritable Bowel Syndrome (IBS).
Frequently Asked Questions
Why do I have to eat gluten before my celiac blood test?
Anti-tTG antibodies are manufactured only when active gluten enters your small intestine. If you adopt a gluten-free diet before testing, your immune system stops producing antibodies, and the test will look completely normal even if you have severe celiac disease.
Why is Total Serum IgA always tested alongside Anti-tTG IgA?
About 1 in 40 celiac patients has an inherited condition called "Selective IgA Deficiency" (their body produces zero IgA). If their total IgA is zero, their Anti-tTG IgA will also be zero (a false negative). Measuring total IgA catches this, alerting the lab to test IgG-based antibodies (DGP-IgG) instead.
Related Laboratory Tests
Tests frequently prescribed together or used as follow-up investigations:
Iron Profile & Serum Ferritin
Serum Iron, Total Iron-Binding Capacity (TIBC), Transferrin Saturation (% Sat), and Stored Tissue Ferritin.
Vitamin D3 (25-Hydroxy Vitamin D)
Total circulating concentration of 25-hydroxyvitamin D (D2 and D3 combined).
Vitamin B12 (Cyanocobalamin)
Total concentration of water-soluble vitamin B12 (cobalamin) in blood serum.
Complete Blood Count (CBC / Hemogram)
Counts and evaluates red blood cells, white blood cells, hemoglobin, hematocrit, and platelets.
Medical & Diagnostic Disclaimer
This guide is published for educational and patient informational purposes only. It is not a substitute for professional medical evaluation, diagnosis, or clinical advice.
A laboratory result that falls slightly outside standard statistical reference intervals does not automatically indicate disease; conversely, a normal result does not guarantee the absence of medical conditions. Only your attending physician can interpret lab findings in the context of your medical history, physical exam, and symptoms.