Abstract

Objective: Congenital anomaly registers allow the rates of anomalies to be monitored and are essential for understanding their epidemiology. We estimate the ascertainment and accuracy of records of Down syndrome (DS) on national and regional registers in England and Wales.

Methods: Probabilistic record linkage was used to match records of DS from three sources: the National Down Syndrome Cytogenetic Register (NDSCR), seven regional members of the British Isles Network of Congenital Anomaly Registers (BINOCAR) and the National Congenital Anomaly System (NCAS). Capture-recapture methods were then used to estimate the ascertainment of each register.

Results: The NDSCR and BINOCAR registers ascertain around 95% of both pre-natally and post-natally diagnosed cases of DS. NCAS collects data only on births and ascertains 55% of cases of DS births, which is currently around 25% of all DS diagnoses. NCAS ascertainment varies according to whether a BINOCAR register covering the same area contributes information to NCAS, varying from 80% in areas where regional registers contribute to 50% where regional registers do not.

Conclusions: Active case finding through regional registers is essential for monitoring congenital anomalies. The ascertainment of the NDSCR and BINOCAR is sufficient to provide reliable epidemiology and surveillance of congenital anomalies, whereas that of NCAS is not.