The epidemiology of coeliac disease in East Dorset 1993-2002: an assessment of the 'coeliac iceberg', and preliminary evidence of case clustering.

BACKGROUND

Coeliac disease (CD) results from mucosal exposure to dietary gluten in genetically predisposed individuals, although other environmental factors may be involved. The seroprevalence of CD is approximately 1%, with a high ratio of undiagnosed to diagnosed cases, leading to the concept of a 'coeliac iceberg'.

AIM: To provide contemporary estimates of the incidence of diagnosed CD and the size of the submerged 'coeliac iceberg', and to seek evidence of disease clustering.

DESIGN

Prospective observational study in a defined local population.

METHODS

Data were collected prospectively for all biopsy-proven cases diagnosed at Poole Hospital, 1993-2002. Age-specific incidence was calculated and point prevalence estimated for cases within the defined study zone. Evidence of disease clustering was sought using a space-time scan statistic based on a Poisson model.

RESULTS

The overall incidence of CD was 8.7 cases/100,000/year (95%CI 7.4-10.1), with a median age at diagnosis of 53 years. Incidence increased progressively during the study period, and the estimated point prevalence of biopsy-proven CD rose from 0.18% to 0.4%. An area of significant space-time clustering was identified, with an incidence of 22.9 cases/100,000/year (95%CI 16.1-31.6), but there was no evidence of seasonality.

DISCUSSION: The submerged component of the 'coeliac iceberg' may be diminishing due to increasing case ascertainment, with a projected ratio of undiagnosed to diagnosed cases as low as 1.5:1. Our identification of clustering must be interpreted with caution, but suggests that an additional environmental factor may influence the pathogenesis of CD.