ARUP's Laboratory Test Directory

Tissue Transglutaminase (tTG) Antibody, IgA : 0097709

Mnemonic: TTG

Ordering Recommendation: Do not use in IgA-deficient individuals; recommended single screening test for celiac disease. In confirmed disease, this test may be used for monitoring.
Methodology: Semi-Quantitative Enzyme-Linked Immunosorbent Assay
Performed: Sun-Sat
Reported: Within 24 hours
Specimen Required: Collect: Serum separator tube.

Specimen Preparation: Separate serum from cells ASAP or within 2 hours of collection. Transfer 0.5 mL serum to an ARUP Standard Transport Tube. (Min: 0.3 mL)

Storage/Transport Temperature: Refrigerated.

Unacceptable Conditions: Plasma or urine. Contaminated, heat-inactivated, or severely hemolyzed specimens.

Stability (collection to initiation of testing): After separation from cells: Ambient: 48 hours; Refrigerated: 2 weeks; Frozen: 1 year (avoid freeze/thaw cycles)
Reference Interval:
19 Units or less: Negative
20-30 Units: Weak Positive
31 Units or greater: Moderate to Strong Positive
Interpretive Data: Presence of the tissue transglutaminase (tTG) IgA antibody is associated with gluten-sensitive enteropathies such as celiac disease and dermatitis herpetiformis. tTG IgA antibody concentrations greater than or equal to 100 Units usually correlate with results of duodenal biopsies consistent with a diagnosis of celiac disease. For antibody concentrations greater than 20 Units but less than 100 Units, additional testing for endomysial (EMA) IgA concentrations may improve the positive predictive value for disease.
Note: Testing for tTG IgA antibodies is recommended as an initial screen to identify patients at risk for celiac disease, and in whom duodenal biopsy should be performed to confirm disease.

Some patients may have positive tTG IgA but negative EMA IgA and/or deamidated gliadin peptide (DGP) IgA results, which may be associated with false positivity or may indicate early disease. Close clinical correlation with continued testing may be indicated in patients with a family history of or who are at increased risk for celiac disease. A positive serology but normal biopsy may also indicate a gluten-free diet (GFD) prior to testing, latent disease, or early enteropathy. Re-challenge with a gluten diet may be recommended if GFD had been initiated prior to subsequent testing. In the case of latent or early disease, HLA DQ2 and DQ8 testing may be necessary to determine risk for disease.

For patients with a high degree of suspicion for celiac disease and who test negative for tTG, EMA and/or DGP IgA tests, selective IgA deficiency should be considered and testing for tTG, EMA and/or DGP IgG antibodies performed.

If serology is negative and suspicion for celiac disease is strong, intestinal biopsy may be warranted. Biopsy is particularly important for patients with diarrhea, steatorrhea, weight loss, failure to thrive, or with inherited genetic deficiencies such Down or Turner syndrome.
CPT Code(s): 83516
Cross References: Celiac Disease (Tissue Transglutaminase Antibody (tTG), IgA), Human RBC tTG (Tissue Transglutaminase Antibody (tTG), IgA), Native tTG (Tissue Transglutaminase Antibody (tTG), IgA), TG2 IgA (Tissue Transglutaminase Antibody (tTG), IgA), tTG, IGA (Tissue Transglutaminase Antibody (tTG), IgA)