From the Guidelines
To diagnose gluten intolerance, the most reliable initial test is the tissue transglutaminase antibody test (tTG-IgA), which has high sensitivity (93%) and specificity (98%) for celiac disease, as supported by the latest guidelines 1. When diagnosing gluten intolerance, several laboratory tests are recommended.
- The tissue transglutaminase antibody test (tTG-IgA) is highly sensitive for celiac disease and should be accompanied by a total serum IgA test to ensure the patient can produce enough antibodies for accurate results.
- Additional tests include deamidated gliadin peptide antibodies (DGP IgA and IgG), endomysial antibodies (EMA), and genetic testing for HLA-DQ2 and HLA-DQ8 markers.
- For definitive diagnosis, an intestinal biopsy is often necessary, performed during an endoscopy while the patient is still consuming gluten, as evidenced by the guidelines for best practices in monitoring established coeliac disease in adult patients 1.
- Blood tests for wheat allergy include IgE antibodies specific to wheat proteins. It's essential to continue eating gluten before testing, as eliminating it can lead to false negatives, and non-celiac gluten sensitivity is diagnosed by ruling out celiac disease and wheat allergy, then observing symptom improvement with gluten elimination and return with reintroduction, as discussed in the systematic review with meta-analysis on the accuracy of serological tests for diagnosing coeliac disease 1. These tests help distinguish between celiac disease, wheat allergy, and non-celiac gluten sensitivity, allowing for appropriate treatment approaches, ultimately improving patient outcomes in terms of morbidity, mortality, and quality of life.
From the Research
Labs for Gluten Intolerance
- The following labs can be used to diagnose gluten intolerance:
- These labs can be used to monitor patients with celiac disease on a gluten-free diet, with tTG antibodies being a hallmark for celiac disease 6
- The sensitivity and specificity of these labs vary, with tTG antibodies having high sensitivity and specificity in detecting celiac disease 3, 5, 4
- However, the sensitivity of tTG antibodies in detecting persistent villous atrophy in patients with celiac disease on a gluten-free diet is low, ranging from 0.45 to 0.50 2
- Different assays for tTG antibodies can give different results, with some being more sensitive than others 6
Comparison of Labs
- A comparison of human tissue transglutaminase antibodies with antigliadin and antiendomysium antibodies found that tTG antibodies had a high positive predictive value of 90% and a negative predictive value of 98% 4
- The presence of human anti-tTG is a reliable indicator for the diagnosis and follow-up of celiac disease 4
- The concordance rate between EMA and tTG antibodies was 100% in patients with untreated celiac disease, 94% in control subjects, and 76% in patients with treated celiac disease 3
Limitations of Labs
- The tests for serum tTG IgA and EMA IgA levels had low sensitivity in detection of persistent villous atrophy in patients with celiac disease on a gluten-free diet 2
- The normalization of tTG-IgA in patients on a gluten-free diet depends on the assay used, with some assays being more sensitive than others 6