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Problems of Ascertainment of Congenital Anomalies

Published online by Cambridge University Press:  01 August 2014

J. Little*
Affiliation:
MRC Medical Sociology Unit, Institute of Medical Sociology, Aberdeen, Scotland
R. A. Carr-Hill
Affiliation:
MRC Medical Sociology Unit, Institute of Medical Sociology, Aberdeen, Scotland
*
Ecole de Santé Publique, Université Catholique de Louvain, Unité d'Epidémiologie, Epid 30.34, Clos Chapelle aux Champs 30, B-1200 Bruxelles, Belgium

Abstract

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Problems of ascertainment bedevil the investigation of the etiology of congenital anomalies in singletons and in multiple births by epidemiological methods. It is shown that the definition of the population of affected births is ambiguous and that the problem of tracing etiology is complicated by the systematic way in which anomalies may be missed at birth. The available methods of dealing with problems of ascertainment are reviewed. Methods of adjusting for possible bias of ascertainment of affected births, by fitting statistical models to data from several sources, have been employed in some previous studies. In these methods, it is assumed that there are no errors of diagnosis or of recording. However, it is shown that there may be discrepancies in recorded diagnoses between sources, rendering this assumption untenable. In these methods, it is also assumed that the model which is the best fit to the data on the ascertained cases in also the best model for the cases which were not ascertained. This assumption is tested indirectly in a retrospective analysis of data from Aberdeen and Belfast collected concurrently through routine recording systems. It is demonstrated that there was a social process in ascertainment which renders the methods of adjusting for bias of ascertainment at best very complicated and at worst inapplicable.

Type
Research Article
Copyright
Copyright © The International Society for Twin Studies 1984

References

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