Tissue Transglutaminase IgA

Label Mnemonic:	TTGA
Epic code:	LAB8013
Order form:	Laboratory Requisition
Supply order:	Supply Order Form
Billing:	Billing Policies
CPT code:	83520

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 reflexes automatically to tissue transglutaminase IgG if total IgA is too low. In these cases, tissue transglutaminase IgA will be resulted as "LOW IGA" and the charges credited.

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 IgA has sensitivity and specificity for celiac disease diagnosis 
of approximately 95% and 99%, respectively, and is thus a front-line 
test in the diagnostic work-up of celiac disease.

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 transglutaminase antibody
   assays in celiac disease. Clin Chem. 50: 2125-35.

Methodology:

Multiplex flow immunoassay

Sample Processing:

Centrifuge at a speed and time necessary to get barrier separation of plasma/serum and cells within 1 hour of collection. Send specimen in original tube. Do Not transfer to another tube.
Each sample must be labeled with at least TWO full patient identifiers (First/Last Name & DOB are sufficient for non-UIHC affiliated clients) to avoid sample rejection/delays.

Sample Storage:

Refrigerate.
All sample storage requirements are intended for delivery to UIHC within 24 hours of collection for testing. If samples won't arrive in this time period, please call the UIHC Core Lab for alternative storage/shipping instructions (319-356-3527).

Transport Instructions:

Place labeled specimen into zip-lock type biohazard bag; seal bag.
Place completed requisition into outside pocket of bag.
Transport in cooler with refrigerated coolant packs.