Does it really matter? Evaluating the Continuous Morbidity Registration—The Nijmegen Project

The maintenance of a programme of continuous registration of morbidity over 40 years calls for the highest praise and, in particular, commendation of the foresight of Frans Huygen, the founding father. However, the Nijmegen team has taken a large, additional step in transferring the information into a database suitable for the analysis of clinical, social, and economic facets of illness in the community as it presents in primary care. The introduction of computerized medical records has opened new opportunities for primary care research, but they are all dependent on highquality, consistent and disciplined recording. It is important to note that this is a fully anonymized database, thus ensuring confidentially. The Steering Committee has been flexible, adapting to new developments over time, but, in the interest of consistency, has retained its original disease classification system (the E-book). The fundamentals of the information system*a fixed registered population database, a composite score of socio-economic status, the recording of episode type by the reporting doctor, regular meetings with the recorders, the definition of continuing disease activity, and the assessment of severity*are all issues which have been similarly addressed in the programme of national morbidity surveys in England and Wales, and mostly resolved in similar ways (1,2). Experience from this project contributed to the recommendations made in the Electronic Health Indicator Data (eHID) Project funded by the European Commission and concerned with optimizing the electronic medical record for use in epidemiology (3). The similarity of many of the findings concur with experience in England and Wales*increase in hypothyroidism but not hyperthyroidism, decrease in duodenal ulcer and in threadworms (4 6). The ability to corroborate the findings of one information system in another is a strong argument for having independent databases, and the ability to do that internationally further supports the conclusions (7). The trend data are particularly valuable, since they are less limited by constraints of sample size, and neatly illustrate the changing nature of primary care with the implied lessons for medical education. New types of analysis applicable to general practice databases are reported and welcome; in particular, the analysis of relapse in irritable bowel disease and of the time between diagnosis and commencement of medication. The analysis of the management of hypertension in relation to guidelines is an example of the increasing use of databases to examine the quality of care. The use of the database to examine illness in families and links between different types of illness all illustrate the potential of primary care databases. However, the complexity of studying comorbidity should not be underestimated (8). As van de Laar emphasized when discussing rare diseases, ‘‘Medical reasoning is not only based on knowledge of diseases, but also on a profound knowledge of epidemiology. ’’ Particularly important points are made in the chapter by van den Dungen and colleagues, addressing the explanations for differences in the estimates of disease prevalence reported in general practice registration networks. In this regard, we cannot ignore the comparatively