Ascertainment and accuracy of Down syndrome cases reported in congenital anomaly registers in England and Wales
George Savva 1* and Joan K Morris 2
1 University of Cambridge, United Kingdom
2 Wolfson Institute of Preventive Medicine, United Kingdom
* To whom correspondence should be addressed. E-mail: george.savva{at}phpc.cam.ac.uk.
Accepted 7 March 2008
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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 on national and regional registers in England and Wales.
Methods: Probabilistic record linkage was used to match records of Down syndrome 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 prenatally and postnataly diagnosed cases of Down syndrome. NCAS collects data only on births and ascertains 55% of cases of Down syndrome births, which is currently around 25% of all Down syndrome 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 Down syndrome, whereas that of NCAS is not.
