Home Biomarkers Anti-Tissue Transglutaminase IgA

Anti-Tissue Transglutaminase IgA

Autoimmune disorder Biomarker

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Collection Type: Blood

Body System

Related System: Autoimmune disorder

Overview

Anti–tissue transglutaminase IgA (tTG‑IgA) is an autoantibody directed against the enzyme tissue transglutaminase in the intestinal mucosa. The blood test measures IgA class antibodies to tTG and is used primarily to screen for and support diagnosis of celiac disease (immune‑mediated enteropathy triggered by gluten). It is indicated in patients with chronic diarrhea, malabsorption, iron‑deficiency anemia, unexplained weight loss, growth failure in children, dermatitis herpetiformis, or in at‑risk groups (first‑degree relatives of people with celiac disease, type 1 diabetes, autoimmune thyroid disease). Results vary with age (titres may be lower in very young children), immune status (selective IgA deficiency can give false‑negative results), and with recent adoption of a gluten‑free diet (antibody levels fall after gluten withdrawal).

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Test Preparation

No special preparation is required

Why Do I Need This Test

Profile: Autoimmune disorder (celiac disease serology) - Symptoms suggesting test: chronic diarrhea, bloating, unexplained anemia, failure to thrive, dermatitis herpetiformis, weight loss - Purpose: diagnose or monitor celiac disease and response to gluten‑free diet - Reasons for abnormal levels: active intestinal autoimmune response to gluten (high); false negatives with IgA deficiency or prior gluten avoidance - Biological meaning: elevated tTG‑IgA indicates immune reaction against gut tissue transglutaminase and correlates with mucosal damage - Lifestyle: adhering to a gluten‑free diet will lower titres; ongoing gluten exposure raises them - Family history: first‑degree relative with celiac disease warrants screening

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Understanding Test Results

<7 U/mL: Negative argues against active celiac disease if the patient is eating gluten and total serum IgA is normal; if IgA deficiency exists, tTG‑IgA may be falsely negative and tTG‑IgG or DGP‑IgG should be used.
7–20 U/mL: Borderline/weakly positive equivocal result; repeat testing, check total IgA, or perform confirmatory testing (endomysial antibody (EMA), duodenal biopsy if indicated) and correlate with symptoms.
>20 U/mL: Positive consistent with celiac disease; higher titres increase the likelihood of villous atrophy.
Many labs and guidelines consider very high titres (≈10× the laboratory upper limit of normal e.g., >70 U/mL if ULN 7 U/mL) as strongly predictive of mucosal damage and, in selected pediatric cases with confirmatory EMA, may allow diagnosis without biopsy.
Trend interpretation: falling titres over months indicate good adherence to a gluten‑free diet; persistently high or rising titres suggest ongoing gluten exposure or refractory disease.
False positives can occur rarely with other autoimmune disorders; false negatives occur with selective IgA deficiency, immunosuppression, or if testing is done after starting a gluten‑free diet.
Always interpret results with clinical context and laboratory reference ranges.

Normal Range

0-7 U/mL

FAQs

Q: What is anti tissue transglutaminase IgA for?

A: Anti-tissue transglutaminase IgA is a blood test that detects IgA autoantibodies against tissue transglutaminase. It’s used to screen for and help diagnose celiac disease and to monitor response to a gluten-free diet. The test is highly sensitive and specific when total IgA is normal; results need caution in IgA deficiency and may prompt intestinal biopsy for confirmation.

Q: What is the normal range for serum anti tissue transglutaminase IgA?

A: Serum anti‑tissue transglutaminase (tTG) IgA is interpreted against the laboratory’s reference range; most labs consider values below the assay upper limit—commonly <4–20 U/mL—as negative. Many clinical labs use <10 U/mL as normal, with values above the lab-specific cutoff (often ≥20 U/mL) considered positive. Always interpret results alongside total IgA and the lab’s reference.

Q: What are IgA levels for celiac disease?

A: Diagnosis relies on IgA-based serology: raised anti‑tissue transglutaminase IgA (tTG‑IgA) and positive anti‑endomysial IgA (EMA) suggest celiac disease. Total serum IgA should be checked because selective IgA deficiency (seen in ~2–3% of cases) can cause false‑negative IgA tests then IgG-based tests (tTG‑IgG or DGP‑IgG) are used. Lab cutoffs vary; interpret against reference ranges and clinical findings.

Q: Is transglutaminase IgA antibody for celiac disease?

A: Tissue transglutaminase (tTG) IgA is the preferred initial blood test for celiac disease because it’s highly sensitive and specific. Always check total IgA concurrently, since IgA deficiency can cause false-negative results; in that case test tTG IgG or deamidated gliadin peptide (DGP) IgG. Positive serology typically prompts gastroenterology referral and an intestinal biopsy to confirm diagnosis.

Q: What is a normal IgA level?

A: Normal adult serum IgA is roughly 0.7–4.0 g/L (70–400 mg/dL). Reference ranges vary by laboratory, age and assay method; children usually have lower values. Mild deviations may reflect infection, immune deficiency, or chronic disease. Significantly high or low IgA should be reviewed by a clinician and interpreted using the lab’s reference interval and medical context.

Q: How to confirm celiac disease?

A: To confirm celiac disease, remain on a gluten-containing diet and get serologic testing (tissue transglutaminase IgA and total IgA; deamidated gliadin antibodies if needed). If serology is positive or suspicion persists, an upper endoscopy with duodenal biopsies provides definitive diagnosis. HLA DQ2/DQ8 testing can help exclude celiac in unclear cases. Improvement on a strict gluten-free diet supports the diagnosis.