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Tissue Transglutaminase (tTG) IgA

Ordering Recommendation

Recommended single screening test for IgA-competent individuals with suspected celiac disease. (IgA testing recommended to identify IgA competence.).

May aid in monitoring adherence to gluten-free diet in celiac disease-confirmed patients.

Mnemonic
Methodology
Semi-Quantitative Enzyme-Linked Immunosorbent Assay
Performed
Mon-Sat
Reported
Within 24 Hours
New York DOH Approval Status
This test is New York DOH approved.
Specimen Required
Patient Preparation:
Collect:
Serum separator tube (SST).
Specimen Preparation:
Separate serum from cells ASAP or within 2 hours of collection. Transfer 0.5 mL serum to a Standard Transport Tube. (Min: 0.3 mL)
Storage/Transport Temperature:
Frozen.
Unacceptable Conditions:
Refrigerated.
Remarks:
Stability:
After separation from cells: Ambient: 48 hours; Refrigerated: 2 weeks; Frozen: 1 year (avoid freeze/thaw cycles)
Reference Interval
3 U/mL or less
4-10 U/mL
Negative
Weak Positive
11 U/mL or greater
Positive
Interpretive Data
Presence of the tissue transglutaminase (tTG) IgA antibody is associated with glutensensitive enteropathies such as celiac disease and dermatitis herpetiformis. tTG IgA antibody concentrations greater than 40 U/mL usually correlate with results of duodenal biopsies consistent with a diagnosis of celiac disease. For antibody concentrations greater or equal to 4 U/mL but less than or equal to 40 U/mL, 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
86364
Components
Component Chart Name
Tissue Transglutaminase (tTG) Ab, IgA
Component Test Code
0097709
LOINC
46128-5
Aliases
Human RBC tTG
Native tTG
TG2 IgA
Tissue Transglutaminase
Tissue Transglutaminase Ab IgA
tTG IgA
tTG, IGA
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