Lab Test

Tissue Transglutaminase (IgA)

TTGA, TTG IgA, Tissue Transglutaminase Antibody, IgA

Test Codes

EPIC: LAB6912, SOFT: TTGAB

Department

Special Chemistry

Specimen Collection Criteria

Collect: One Gold-top SST tube. (Minimum Whole Blood: 2.0 mL)

Physician Office/Draw Specimen Preparation

Let specimen clot 30-60 minutes then immediately centrifuge to separate serum from cells. Refrigerate (2-8°C or 36-46°F) the centrifuged collection tube within two hours of collection. (Minimum Serum: 0.5 mL)

Preparation for Courier Transport

Transport: Centrifuged collection tube, refrigerated (2-8 °C or 36-46 °F). (Minimum Serum: 0.5 mL)

Rejection Criteria

Plasma specimens.

Severely hemolyzed, lipemic or icteric specimens.   

In-Lab Processing

Let specimen clot 30-60 minutes then immediately centrifuge to separate serum from cells. Room temperature is acceptable for a maximum of two hours. (Minimum: 0.5 mL)

Storage

Specimen Stability for Testing:

Centrifuged SST Tubes and Microtainers® with Separator Gels
Room Temperature (20-26°C or 68-78.8°F): 8  hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): Unacceptable

Red-top Tubes and Microtainers® without Separator Gels
Room Temperature (20-26°C or 68-78.8°F): 2 hours
Refrigerated (2-8°C or 36-46°F): Unacceptable
Frozen (-20°C/-4°F or below): Unacceptable

Serum Specimens (Pour-Overs)
Room Temperature (20-26°C or 68-78.8°F): 2 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): 3 months

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 7 days

Laboratory

Royal Oak Special Testing Laboratory

Performed

Tuesday, Wednesday, Friday.
Results available in 2 business days.

Reference Range

Negative: Less than 20 units.
Weak Positive: 20 – 30 units.
Moderate-Strong Positive: Greater than 30 units.

Test Methodology

Enzyme-Linked Immunosorbent Assay (ELISA).

Interpretation

Tissue transglutaminase antibodies appear to be highly specific for celiac disease and are useful to screen high-risk populations (e.g. first degree relatives of celiac patients, insulin dependent diabetics, etc.) for celiac disease. However, histologic confirmation is required for diagnosis. Patients should not begin a gluten-free diet until after intestinal biopsy has been performed and the diagnosis is established. Serial tissue transglutaminase antibody testing may at times be useful to monitor dietary compliance.

Note: The endomysial antigen has been identified as the protein cross-linking enzyme known as tissue transglutaminase. Detection of tissue transglutaminase antibodies is an aid in the diagnosis of certain gluten-sensitive enteropathies, such as celiac disease and dermatitis herpetiformis. Human tTg IgA antigen is used in this assay.

Clinical Utility

Tissue transglutaminase is an enzyme that is normally located within endomysial cells. IgA autoantibodies to tissue transglutaminase have been shown to be highly correlated with active celiac disease.

Note: Patients with IgA deficiency may have falsely negative test results. If there is a high degree of suspicion for celiac disease, tissue transglutaminase antibodies (IgG) and an IgA level should be requested.

CPT Codes

83516
LOINC: 46128-5

Contacts

Last Updated

1/13/2023

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