Estimating the incidence of coeliac disease with capture-recapture methods with four geographic areas in Italy

Study objective - To estimate the incidence rate of newly diagnosed cases of coeliac disease in Italy. Design - This was a descriptive study of coeliac disease incidence in the period 1990-91. Setting - During 1990-91 newly diagnosed cases of coeliac disease were signalled by several sources including diagnostic records of departments of paediatrics, general medicine and gastroenterology, national health service records for the supply of gluten free diets and the archives of the Italian Coeliac Society. Patients - Altogether 1475 cases were flagged throughout Italy, 478 of whom were Selected, corresponding to 270 individual patients from a target population resident in four areas: Provices of Turin and Cuneo (Piedmont Region, northern Italy); Province of Brescia (Lombardia Region, northern Italy); Umbria Region (central Italy) and Sardinia Region (insular Italy). Only for these areas were patients flagged from several sources and the reference population was identifiable. Main results - The overall crude incidence rates for all ages per 100 000 residents per year were 2.4, 2.7, 1.5, and 1.7 in the four areas, respectively. The childhood cumulative incidence rates (aged less than or equal to 15 years) per 100 000 live births were 143, 141, 72, and 80 respectively. The mean ages at diagnosis were similar for both childhood and adult cases throughout the areas - these were around 4 and 34 years respectively. For each area, the incidence rate was constantly higher in main city than elsewhere. Using the capture-recapture method, an estimated completeness of case archives of 0.84 was obtained, whereas this figure was only 0.47 for hospital sources. Conclusions - This population based study of the disease rather than different environmental patterns affecting the clinical presentation.