Recommended single screening test for celiac disease. IgA testing recommended to identify IgA deficiency. Use IgA test in individuals who are IgA competent. May aid in monitoring adherence to gluten-free diet.
- Patient Preparation
- 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
- Unacceptable Conditions
- Plasma or urine. Contaminated, heat-inactivated, or severely hemolyzed specimens.
- After separation from cells: Ambient: 48 hours; Refrigerated: 2 weeks; Frozen: 1 year (avoid freeze/thaw cycles)
4-10 U/mL: Weak Positive
11 U/mL or greater: Positive
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.
|Component Test Code*||Component Chart Name||LOINC|
|0097709||Tissue Transglutaminase (tTG) Ab, IgA||46128-5|
- Human RBC tTG
- Native tTG
- TG2 IgA
- Tissue Transglutaminase
- Tissue Transglutaminase Ab IgA
- tTG IgA
- tTG, IGA