Clinical Practice Change:
The Shared Health Immunology Laboratory at St Boniface Hospital will be changing its testing platform for workup of suspected celiac disease and dermatitis herpetiformis.

Background Information:
Antibodies against tissue transglutaminase support the diagnosis of gluten-sensitive enteropathy (celiac disease). Tissue Transglutaminase Antibodies (TTG-IgA) will be positive in about 98% of patients with celiac disease who are on a gluten-containing diet.

Changes in Test Procedure:

1. Testing for TTG IgA will be changing from an ELISA to a Chemiluminescent (CLIA) method.
2. Pediatric positive samples ≥10 AU/ml will automatically reflex to endomysial antibody testing by immunofluorescence (all instances).
3. Adult positive samples in the range 10.0 – 100.0 AU/ml will automatically reflex to Endomysial antibody testing by immunofluorescence (first instance only).
4. The new method can also identify IgA Deficiency (IgA ≤0.07 g/L) in patients. A separate request for total IgA is no longer required. Samples determined to be IgA deficient, and all children ≤3years of age, will automatically reflex to Deamidated Gliadin IgG.

References/Resources:
Test: TTG IgA Laboratory Information Manual – TTGA
Delphic Code: TTGA
Delphic Labels: CLIA
Sample: Serum 1.0 ml
Normal Range: 0.0 – 9.9 AU/ml
Availability: Weekdays (3-5day TAT)
Requisition: Immunology Autoimmune Laboratory Requisition
Test: Deamidated Gliadin IgG Laboratory Information Manual – DGG
Delphic Code: TTGA
Normal Range: 0.0 – 9.9 AU/ml
Availability: Weekdays (3-5day TAT)

Patient Impact:

• As no international reference serum exists for antibodies against tissue transglutaminase, the calibration and reporting is in arbitrary units (AU/ml). There is no linear correlation between the CLIA and ELISA methods. Any patients being followed for treatment response or to monitor disease activity should have baseline data reevaluated.

System Improvements:

1. Will reduce the inappropriate ordering of Tissue Transglutaminase IgG and Deamidated Gliadin
2. Improved TAT

Contact Information:

• Dr. Ping Sun, Hematopathologist, Medical Director Hematology & Immunology, Shared Health Manitoba, 204-787-4682 or
• Jason Warren, Immunology Technical Director, Shared Health Manitoba, 204-471-0370 or

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Submitted by Tamara Burnham, Collaborative Practice Lead