Overview
Gluten constitutes more than 85% of the protein content of wheat and is mainly a conglomerate of gliadin and glutenin. These proteins are rich in the amino acids glutamine and proline and therefore belong to a group known as prolamines.
It is present in several commonly consumed grains and foods, including wheat, barley, rye, bread, pasta, pizza, and cereals. Although gluten provides no essential nutrients, its unique physical and chemical properties make it a valuable ingredient in baking and food processing. It improves texture, elasticity, volume, and moisture retention in processed foods.
However, in individuals with celiac disease, gluten proteins trigger a harmful immune response that leads to intestinal damage and systemic complications.
Pathophysiology
In genetically susceptible individuals carrying HLA-DQ2 or HLA-DQ8 molecules, dietary gluten triggers a T-cell–mediated autoimmune enteropathy. This immune reaction results in chronic inflammation, villous atrophy, and damage to the intestinal lining, leading to impaired nutrient absorption.
The disease process involves a complex interaction between environmental exposure (gluten), genetic predisposition, and immunological mechanisms.
A notable neurological manifestation is gluten ataxia, in which antibodies produced against gluten mistakenly attack the cerebellum, affecting balance, motor coordination, and muscle tone, resulting in progressive ataxia.
Functions of Gluten
It serves several functional roles, particularly in food science and grain biology. It adds protein content, texture, and flavor to foods and acts as a binding agent that helps processed foods retain shape and structure.
Gluten-containing whole grains are also described as sources of antioxidants, dietary fiber, B-complex vitamins, vitamin E, magnesium, iron, folic acid, and other micronutrients, provided they are tolerated.
In grains, gluten proteins support germination and seedling development. Consumption of whole grains is associated with lower cholesterol levels and improved blood sugar regulation, though these benefits do not apply to individuals with gluten-related disorders.
Indications for Estimation
Evaluation for gluten-related disorders is indicated in a wide range of clinical conditions, including:
- Celiac disease
- Non-celiac gluten sensitivity / non-celiac wheat sensitivity (NCGS/NCWS)
- Cerebellar ataxia
- Dermatitis herpetiformis
- Type 1 diabetes mellitus
- Unexplained weight loss
- Malabsorption
- Persistent or unexplained gastrointestinal symptoms such as chronic diarrhea, bloating, and abdominal pain
- Unexplained iron deficiency anemia
- Unexplained elevation of liver enzymes
- Delayed puberty
Dermatitis Herpetiformis
Dermatitis herpetiformis (DH) is described as the “celiac disease of the skin” and represents a cutaneous manifestation of gluten-sensitive enteropathy.
Patients with DH have serum IgA antibodies against epidermal transglutaminase and tissue transglutaminase, confirming the autoimmune nature of the condition and its strong association with gluten sensitivity.
Diagnostic Approach
When celiac disease is suspected, further evaluation includes:
- Endoscopy with intestinal biopsy, which remains the gold standard for confirming villous atrophy
- Capsule endoscopy, used selectively to visualize the entire or distal small intestine
Blood sample collection requires a fasting serum sample, with 2–3 mL of blood collected in a plain red-capped tube. Samples are stored at 2–8°C and rejected if hemorrhagic, icteric, or grossly lipemic.
Methods of Estimation
Diagnostic methods include:
- Serology: Anti-gliadin antibodies (IgA & IgG), anti–tissue transglutaminase (anti-tTG), anti-endomysial antibodies (EMA)
- Genetic testing: HLA-DQ2 and HLA-DQ8 typing
- Immunoassays: ELISA for gluten peptides
- Advanced methods: Mass spectrometry and PCR-based detection
- Food testing: Cross-contamination checks and labeling compliance
IgA-based tests are more sensitive for celiac disease, while IgG antibodies are useful in IgA-deficient individuals.
Limitations and Utility
In patients with extremely low total IgA levels, antigliadin antibody results may be unreliable. Overall, test sensitivity and specificity are approximately 90%.
Clinically, gluten testing helps:
- Diagnose and manage celiac disease
- Determine the need for a gluten-free diet
- Monitor response and compliance with dietary restrictions
- Ensure accuracy of gluten-free food labeling
- Prevent cross-contamination during food production
