Diagnosis of Coeliac Disease
Diagnosis of coeliac disease involves a thorough combination of blood tests, genetic markers, and intestinal biopsies. Because coeliac disease can mimic many other conditions, a proper diagnosis requires careful evaluation and should always be conducted while the individual is still consuming gluten. Stopping gluten prematurely can cause false-negative results.
The first step is a blood test to check for elevated coeliac-related antibodies. The most commonly used is the tissue transglutaminase antibody (tTG-IgA) test, which is highly sensitive and specific. If IgA deficiency is suspected, the total serum IgA is measured, or alternative tests like DGP-IgG (deamidated gliadin peptide) may be used. Elevated antibody levels strongly suggest coeliac disease, particularly when symptoms are present.
Diagnosis of Coeliac Disease
If blood tests indicate coeliac disease, the next step is usually an upper endoscopy with small bowel biopsy. This procedure allows the doctor to view the duodenum (first part of the small intestine) and take tissue samples. The hallmark findings include villous atrophy, crypt hyperplasia, and increased intraepithelial lymphocytes — all indicative of gluten-induced damage. Biopsies remain the gold standard for confirmation.
In some cases, especially among children with high antibody levels and symptoms, diagnosis can be made without a biopsy, particularly if genetic testing confirms the presence of HLA-DQ2 or DQ8. However, this approach is more common in Europe than in other regions and must follow strict diagnostic criteria.
Genetic testing for HLA-DQ2 and HLA-DQ8 can also be useful in ambiguous cases. While a positive result doesn’t confirm the disease (since many people carry the genes without developing it), a negative result effectively rules it out, as these genes are present in over 99% of affected individuals.
Diagnosis of Coeliac Disease
If someone has already started a gluten-free diet before testing, a gluten challenge may be recommended. This involves reintroducing gluten under medical supervision, usually over a 6–8 week period, followed by antibody testing or biopsy. This process can be physically uncomfortable and must be monitored closely.
Additionally, bone density scans, vitamin and mineral assessments, and liver function tests may be ordered to evaluate for complications or coexisting conditions, especially in long-term undiagnosed cases.
A correct diagnosis of coeliac disease is essential before initiating lifelong dietary changes. Misdiagnosis can lead to unnecessary restrictions, while delayed diagnosis increases the risk of long-term health issues. Therefore, all testing must be done methodically, and ideally under the care of a gastroenterologist or specialist dietitian.
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