Tissue Transglutaminase IgG
Label Mnemonic: TTGG
Epic Lab Code: LAB8014
Downtime Form: A-1a General Laboratory Requisition
Chemistry
6240 RCP
356-3527
Specimen(s):
Plasma
Collection Medium:
Plasma Separator Tube 4.5 mL
Minimum:
Adult - 3 mL plasma separator tube
Pediatric - two Microtainer® devices
Testing Schedule:
24 hrs/day, 7 days a week, including holidays.
Turn Around Time:
3 hours (upon receipt in laboratory)
Reference Range:
Negative: <15 U/mL
Positive: 15 U/mL or greater

This testing is not directly orderable and is only available as reflex to tissue transglutaminase IgA if total IgA is too low for tissue transglutaminase IgA measurement.
Comments:
Celiac disease or gluten-sensitive enteropathy is an immune- mediated disorder that primarily affects the gastrointestinal tract and is characterized by chronic inflammation of the small intestine mucosa, which may result in atrophy of intestinal villi, malabsorption and a variety of clinical manifestations. It is caused by a pathological intolerance to gliadin, the alcohol-soluble fraction of gluten in wheat, rye and barley. Celiac disease manifests at any age with a peak onset in early childhood. Recent studies now suggest that its prevalence is in the range of 0.5 to 1.0% of the U.S. population with certain populations having an increased prevalence of celiac disease. Celiac disease is also associated with selective IgA deficiency and autoimmune disorders. The US incidence rate is 1:130, which is similar to European countries. Diagnosis of celiac disease is based on a combination of clinical symptoms and the following factors: IgA and/or IgG antibodies to tissue transglutaminase (TTG) IgA and/or IgG antibodies to deamidated gliadin Endomysial IgA and/or IgG antibodies Human leukocyte antigen (HLA)-DQ2 or DQ8 genotypes Biopsy of the small intestine (demonstrating flat mucosa) Or a patient's satisfactory response to a gluten-free diet (GFD). IgA deficiency is more common in the celiac disease (2-3%) versus the average population (0.1-0.2%). Therefore, it is recommended that IgG antibodies to deamidated gliadin be determined if there is total IgA deficiency. TTG IgG has much lower sensitivity (44%) than TTG IgA in patients without IgA deficiency. Therefore, it is not recommended to test TTG IgG except when there is IgA deficiency. References: 1. The National Institutes of Health (NIH) Consensus Development Conference on Celiac Disease, NIH Consensus Development Conference Statement, June 28-30, 2004. 2. van der Windt, et al. Diagnostic Testing for Celiac Disease Among Patients with Abdominal Symptoms: a Systematic Review. JAMA May 2010, 303(17);1738-46. 3. G. Holmes, C. Catassi, A. Fasano. Fast Facts: Celiac Disease. 2nd Edition; August 2009, 57-63. 4. Rashtak S., Ettore M., Homberger H., Murray J. Comparative Usefulness of Deamidated Gliadin Antibodies in the Diagnosis of Celiac Disease. Clin Gastroenterol Hepatol April 2008, 6(4); 426- 32. 5. Green, P.H., Jones. R. Celiac Disease: A Hidden Epidemic. 2006, 45-48. 6. Van Meensel B, Hiele M, Hoffman I, et al. 2004. Diagnostic accuracy of ten second-generation (human) tissue transgluta¬minase antibody assays in celiac disease. Clin Chem. 50: 2125–35.
Methodology:
Multiplex flow immunoassay
CPT Code:
83520