Celiac Disease and Gluten-Free Diet Support
- Questions? Join our forum: Nearly 1 MILLION POSTS, and over 62,000 MEMBERS!
Follow / Share
|Get Email Alerts|
- Safe Gluten-Free Food List (Safe Ingredients)
- Unsafe Gluten-Free Food List (Unsafe Ingredients)
- Gluten-Free Alcoholic Beverages
- Celiac Disease Symptoms
- The Gluten-Free Diet 101 - A Beginner's Guide to Going Gluten-Free
- Interpretation of Celiac Disease Blood Test Results
- Is Buckwheat Flour Really Gluten-Free?
Tests for IgA Antibodies to Tissue Transglutaminase Vary Too Much For Easy Commutability
Celiac.com 08/26/2015 - People with IgA antibodies to tissue transglutaminase (anti-tTg) likely have a higher risk for celiac disease. Some clinicians and researchers have suggested that common multiples of the upper limit of normal (ULN) be useful tool in improving diagnostic pathways, as well as continuity between tests.
However, a new study suggests that both sensitivity and specificity of tests for IgA antibodies to tissue transglutaminase vary widely by individual kit, and that their test values are not easily commutable using common multiples of the ULN to correct for inter-assay variations. Commutability just means the ability to make sure that two different tests really are equal. If results of different tests are commutable, it means that they are equal. In this case, the term applies to test results for various representative samples from healthy and diseased individuals.
For the study, the research team recently looked at the use of immunoassays for the detection of IgA antibodies to tissue transglutaminase, and also sought to better understand of the significance of multiples of the upper limit of normal and inter-assay correlations. The research team included B.B. Suh-Lailam, K.W. Davis, and A.E. Tebo. Using indirect immunofluorescence assay (IFA) as reference, the team assessed characteristics of four anti-tTG IgA assays relative to endomysial IgA (EMA).
They also assessed commutability between anti-tTG immunoassays and/or EMA based on manufacturer's recommended cut-off values and three common multiples of ULN (3×, 5× and 10×). To do this, they analyzed samples from 200 patients and 100 healthy individuals.
They found that, at manufacturer's cut-off, the sensitivities for the tTG assays ranged from 72.5% to 98.6% and specificities from 60.3% to 99.2%. The percent positive agreements between any anti-tTG and EMA or any two anti-tTG immunoassays varied from 56.7% to 98.0% and 46.7% to 100.0%, respectively.
At 3×, 5× or 10× ULNs, the inter-rater reliability as measured by Cohen κ between any two anti-tTG assays were quite variable and ranged from 0.28 to 0.96, 0.26 to 0.89 or 0.13 to 0.78, respectively.
Furthermore, the percent positive agreements between any two anti-tTg IgA immunoassays ranged from 83.1% to 98.2%, 92.0% to 100%, or 100%, at 3×, 5× or 10×, respectively.
Hence, the team's basic takeaway that result parameters for tTG IgA immunoassays or tTG IgA and EMA vary by kit, and thus common multiples of the ULN are not enough to correct for variation between tests.
Celiac.com welcomes your comments below (registration is NOT required).
Increased Detection of Celiac Disease with Measurement of Deamidated Gliadin Peptide Antibody Before Endoscopy
Celiac disease is frequently mis-diagnosed.... [READ MORE]
Endoscopic Biopsy Technique in the Diagnosis of Celiac Disease: One Bite or Two?
Getting high-quality biopsy specimens is key to making accurate celiac disease diagnoses.... [READ MORE]
Vitamin Deficiencies and Celiac Disease
It is common for many people with celiac disease to have vitamin deficiencies.... [READ MORE]
Fingertip Rapid Point-of-care Test in Adult Case-finding in Celiac Disease
Celiac disease remains seriously under diagnosed in adults and, in many places, often takes years and even decades to diagnose.... [READ MORE]
Jefferson Adams is a freelance writer living in San Francisco. His poems, essays and photographs have appeared in Antioch Review, Blue Mesa Review, CALIBAN, Hayden's Ferry Review, Huffington Post, the Mississippi Review, and Slate among others.
He is a member of both the National Writers Union, the International Federation of Journalists, and covers San Francisco Health News for Examiner.com.View all articles by Jefferson Adams
In Celiac.com's Forum Now:
Celiac.com Celiac Disease & Gluten-Free Diet Forum - All Activity