Executive summary
- Test while eating gluten: avoid starting a gluten-free diet before serology — it can normalise tests and delay diagnosis.
- First-line: total IgA + IgA tissue transglutaminase (tTG).
- IgA deficiency: use IgG-based tests (e.g., IgG EMA/IgG tTG depending on local lab offering) and refer if suspicion remains high.
- Confirmatory diagnosis usually needs specialist assessment (often duodenal biopsy in adults) before committing to lifelong dietary treatment.
Who to test (high-yield primary care triggers)
- Unexplained iron deficiency anaemia or folate/B12 deficiency.
- Persistent GI symptoms: chronic diarrhoea, bloating, abdominal pain, weight loss, IBS-type symptoms with red flags.
- Associated conditions: type 1 diabetes, autoimmune thyroid disease, first-degree relative with coeliac disease.
- Bone health: premature osteoporosis/osteopenia, recurrent fractures with no clear cause.
Testing pathway (practical and pitfalls)
- Order together: total IgA + IgA tTG.
- If total IgA low/deficient: use an IgG-based serology strategy per local lab (and refer if clinical suspicion persists).
- Borderline/discordant results: don’t “reassure and discharge” if the story fits — discuss/referral is appropriate.
- Do not start gluten-free before testing; if the patient already has, a supervised gluten challenge may be required (specialist-led).
Frequently asked questions
Can I diagnose coeliac disease purely on blood tests in adults?
In adults, diagnosis is usually confirmed via specialist assessment (often including duodenal biopsy) before recommending lifelong dietary therapy. Blood tests guide likelihood and referral urgency.
What is the commonest primary-care “miss” in coeliac testing?
Testing after the patient has started a gluten-free diet. Even a few weeks of gluten reduction can reduce antibody titres and produce false negatives.
Transparency
This page is an educational, clinician-written summary of publicly available NICE guidance intended for trained healthcare professionals. It uses original wording (not copied text) and should be used alongside the full NICE source, local pathways, and clinical judgement. Doses provided are for general reference; always check the BNF/SPC.