Tissue Transglutaminase (TTG)
Department of Immunology
Indication
Highly sensitive and specific test for coeliac disease or dermatitis herpetiformis.
Notes
- This assay is used as a primary screen for coeliac disease. Confirmatory IgA anti-endomysial (AEA) is performed on all positives.
- AEA will not be performed independently of TTG.
- The assay has a built-in check for detectable IgA, and when low serum immunoglobulins will also be measured. If IgA<0.2g/L the sample will be referred for IgG endomysial antibodies.
- In children, with a TTG >100 this is highly suggestive of coeliac disease (so a biopsy may not be necessary).
- TTG requests will not routinely be processed within a year of a previous negative TTG.
- Serological assays for the investigation of Coeliac disease are only accurate if the patient is on a gluten - containing diet, e.g., gluten in more than 1 meal per day, for at least 6 weeks prior to testing.
Sample Requirements
Adult
5ml Gold-top SST tube or 3.5ml Rust-top gel tube (Trust users only)
Paediatric
1ml Serum Sample
Turnaround Times
7 days
Range (U/ml) | Interpretation |
---|---|
< 7 | Negative |
7 - 10 | Equivocal |
> 10 | Positive |
Time Limit for Add-ons
2 weeks (whilst stored at 2°C - 8 °C)