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UW Health SMPH
American Family Children's Hospital

UW Hospital and Clinics Lab Test Directory

Test Name: Tissue Transglutaminase Ab, IgA

Test Code(s): TTGIGA / XTTGA

CPT Code(s): 83516

Methodology: ELISA

Clinical Significance: Tissue Transglutaminase antibody assays are now considered the most sensitive and specific serologic tests for celiac disease. Although classically considered a gastrointestinal disorder, celiac disease can actually present with a variety of intestinal and extra-intestinal symptoms. It is an immune-mediated disorder triggered by exposure to specific dietary proteins (glutens) in wheat, barley, and rye. Affected individuals will show inflammation and atrophy of the small intestine on biopsy; this is the gold standard for diagnosis. Treatment is a gluten-free diet for life.  

Days Performed: Mon-Fri, dayshift - day varies.

Turnaround Time: Stat: Not available stat.
Routine: 2 - 3 working days.


Specimen Requirements

Specimen: Blood

Collection Container: Preferred: Red top
Also Acceptable: Red cap with yellow ring (SST)

Collection Volume: Preferred: 3 mL
Pediatrics: 1 mL

Sample Analyzed: Serum

Volume Required: Preferred: 1 mL
Pediatrics: 0.3 mL

Specimen Processing: Centrifuge. Transfer cell-free serum to clear plastic vial. Refrigerate.

Specimen Transport: Transport specimen to laboratory. Transport with coolant pack if coming from satellite or outreach location.

Unacceptable Criteria: Grossly hemolyzed or grossly lipemic samples
Plasma and other body fluids

Stability: Ambient: 2 days
Refrigerated: 14 days at 2-8C
Frozen: 3 months at -20C or lower


Interpretation

Reference Interval:

6 years and up:

 

Negative <20 units
Borderline 20-30 units

Moderate to Strong

Positive

>30 units

 

Assay peformance not established for pediatric population under age 6

Test Limitations:

This test has high sensitivity and specificity for biopsy proven celiac disease. A small portion of the population is IgA deficient and will have a negative IgA TTg antibody test. If the patient has a high clinical suspicion of celiac disease and the IgA TTg antibody test is negative, quantitative serum IgA levels should be measured. If the patient is IgA deficient, IgG TTg antibody testing is recommended.  The Immunology Laboratory will review IgG TTg antibody requests prior to sending them out.

 

Individuals on a gluten-free diet may have a negative IgA TTg result.

 

 

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