Methodological issues in using prescription and other databases in pharmacoepidemiology

Abstract

ABSTRACT

Development in technology has led to a considerable increase in the number of individual-based registers

and databases, that may be of value in pharmacoepidemiological research, and the number of studies that

are based on these secondary data may be expected to increase. The focus of this paper is to review methodological

problems related to use of such databases in pharmacoepidemiological studies with respect to the

four basic types of associations which can be observed in an observational study: 1) bias, 2) confounding,

3) chance or 4) causal. The following factors will affect the value and validity of registries and databases:

1) the completeness of registration of persons, 2) the validity and degree of completeness of the registered

data, 3) the size of the data source, 4) the registration period, 5) data accessibility, availability, and costs, 6)

data format, and 7) the possibilities of linkage with other data sources. The importance of these issues

depends on the use of the data and on the problems they have to address. The Nordic countries have a

unique possibility of record-linkage between registries because of the civil registry number assigned to

every citizen at birth. In pharmacoepidemiological research this gives us the opportunity to study different

outcome events in relation to drug use, and this has been extensively used in the Danish pharmacoepidemiological

approach. The Nordic countries could play a leading role in future pharmacoepidemiological

research. This, however, requires considerably more efficient and comprehensive use of the collected data

on which the society has spent many resources for other purposes.