Referral guideline – Coeliac disease diagnosis

Introduction

Coeliac disease is common (1/100) and has a wide spectrum of presentations.

Accurate diagnosis is important as the disease is life-long.

An empirical gluten free diet makes diagnosis difficult or sometimes impossible.

Coeliac serology

Coeliac serology is used to test for coeliac disease (antibodies are elevated in the majority of coeliacs and a small minority of the general population). False positive elevation of coeliac antibodies is not unusual. Seronegative coeliac disease occurs but is rare.

When testing for coeliac disease, a patient must be on a diet containing adequate gluten. Ensure each of the following tests are performed:

• tissue transglutaminase – TTG IgA
• IgG dependent antibody (also known as deamidated antigliadin – DAG IgG)
• total IgA (as IgA deficiency can interfere with IgA antibodies).

In additional to coeliac serology, a duodenal biopsy is essential for diagnosis in most patients.

The “gene test”

HLA DQ2 or 8 is present in all patients with coeliac disease, but also in 30% of the general population. It should NOT be used to make a diagnosis or to justify gluten restriction.

HLA testing is primarily used to exclude coeliac disease in first degree relatives of index cases.

If HLA DQ2 or 8 negative, they will never develop coeliac disease and can be reassured. Specialist referral is unnecessary.

If HLA DQ2 or 8 positive, but seronegative for coeliac antibodies and without symptoms, they should not be placed on a gluten free diet. They may still develop coeliac disease in the future but specialist referral is unnecessary at this stage. In such patients, coeliac antibodies should be re-tested if symptoms develop, with appropriate referral at that point.

GP management

Request the following blood tests while maintaining gluten in the diet:

1. TTG IgA (tissue transglutaminase antibodies)
2. DAG IgG (deamidated antigliadin antibodies)
3. Total IgA.

Do not stop gluten. Emphasize the importance of continuing a normal diet with gluten until the diagnosis is confirmed, usually by duodenal biopsy.

When to refer

• If abnormal coeliac serology is identified
• Do not refer patients on the basis of HLA testing without serology

Essential referral info

• Details and severity of any clinical symptoms
• Results of coeliac serology
• Height/Weight or BMI, if type 2 diabetes suspected
• Confirmation that the patient has been recommended to continue a normal diet
• Patient details
• Medicare number
• Parent/carer name and contact details
• Referring clinician details (name, contact details, provider number, date and length of referral)

Helpful referral info

• Family history of coeliac disease, autoimmune conditions or gastrointestinal malignancy