Introduction: The phenotypic composition of intraepithelial lymphocytes (IELs) changes after development of coeliac disease. It is not known whether this precedes symptoms or histological changes but persists despite dietary adherence and mucosal healing. We previously demonstrated that the proportion of surface CD3+ IELs and of CD3+ gamma-delta (GD) TCR cells are co-related variables in the diagnosis of coeliac disease such that an algorithm (CD3+(2x GD) >/=100) effectively separates those with coeliac disease from those without regardless of mucosal healing.
Method and patients: Patients who underwent routine flow cytometry on duodenal biopsies were retrospectively categorised as active coeliac disease (ACD – TTG>7, Marsh 2+), treated coeliac (Marsh 1 or less, TTG-), or non coeliac (TTG never >7, Marsh 1 or less). IELs were separated and immunostained for flow cytometry as previously described. In 12 cases, 2 individual biopsies were subjected to separate analysis of CD3, TCR GD and alpha beta as a reduced protocol alongside our usual 10 biopsy extended marker panel for validation purposes.
Results: n=84 non-coeliac, n=84 active coeliac and n=73 treated coeliac. 5/157 (3.2%) patients with coeliac disease (1 active, 4 in remission) had a score <100, 5/84 (6%) of non- coeliac patients had a score >100 (sens 96.8%; spec 94%; PPV 96.8%; NPV 94%), of which one was an identical twin of a patient with proven coeliac disease and another had a father with EATL. The reduced protocol validation group showed good correlation with the extended panel (R2 = 0.84) – only 1 out of 12 patients would have been misclassified in this group
Discussion: The diagnostic algorithm we have developed based on both CD3 and GD TCR IEL proportions remains of diagnostic value independent of mucosal healing and dietary adherence. A reduced protocol technique performs well and will be used to assist validation across other centres.