National database of patients visiting rheumatologists in The Netherlands: the standard diagnosis register of rheumatic diseases. A report and preliminary analysis.

I most countries, little is known about the number Netherlands, patients do not have direct access to rheumatologists, but have to present with the rheumof patients who attend rheumatological out-patient clinics, or about the type, characteristics and severity atic complaints to a general practitioner (GP) first. Nearly all people are registered with a GP. The GP of their diseases, because existing registers predominantly focus on hospitalized patients. Perhaps the can decide whether or not it is necessary to refer someone, for instance to a rheumatologist, another best known example of a rheumatology register is the ARAMIS (American Rheumatism Association medical specialist or a physiotherapist. In addition to the primary focus of the register, the SDR can be used Medical Information System) database [1–4]. However, this is not a register that can be used to to select or sample cohorts of patients with specific diagnoses for clinical or epidemiological research. This study the morbidity patterns and the number of patients with particular diseases in rheumatological system for collecting data could be used in other countries to enable comparison of rheumatological practices because the data do not include all patients attending out-patient clinics. Recently, three articles practice at an international level. In this report, we first describe the set-up and were published describing morbidity patterns in paediatric rheumatology clinics in the USA [5], the UK [6 ] contents of the register. We then present the results of analyses of data from the 1993 database of the SDR and Canada [7]. This article describes morbidity patterns in rheumatology out-patient clinics in general. to give an impression of morbidity patterns in rheumatological practices in the Netherlands. In the discusUntil 1978, little was known about the attendance of rheumatological out-patient clinics in the sion, we address some issues about the strengths and weaknesses of the SDR. Netherlands, even though 95% of the patients of rheumatologists are treated at out-patient clinics. For DESCRIPTION OF THE SDR that reason, in 1978 the Rheumatic Diseases Research Committee of TNO (The Netherlands Organization of Aims Applied Scientific Research) set up the so-called The SDR was set up to provide national data on Standard Diagnosis Register of Rheumatic Diseases the morbidity of patients who visit rheumatologists. (SDR). The focus of this register is the collection of Therefore, the participants in the register are practising representative data from the participating rheumatorheumatologists. In addition to receiving aggregated logical practices, to form a national database. data, each participant is also provided with data from Data from the SDR can be used to gain insight into his or her own practice, so that he or she can compare the morbidity pattern of the ‘average’ Dutch rheumatohis or her own practice population and morbidity logical practice and into differences between practices patterns with the national data or with relevant suband trends over the years [8]. If the participation rate groups (e.g. university hospitals vs other hospitals). is high enough, estimates of the 1 yr new episode Another important goal of the SDR is to facilitate the incidence and the 1 yr consulting prevalence of the sampling or selection of patients for clinical research, various rheumatic diseases or complications at the level especially multicentre trials. of rheumatological practices can be obtained. These data are not representative for the general population, Participation rates but with such information it is possible to estimate the When the SDR started in 1978, the yearly collection proportion of patients with a particular disease, who of data was limited to rheumatological diagnoses and are referred to rheumatologists, if epidemiological data demographic information. The participation rate has from the general population are also available. In The increased substantially from 1988 onwards, when the SDR was financially supported by the Dutch Ministry of Health and the Dutch League Against Rheumatism. Submitted 9 October 1997; revised version accepted 11 In addition, the organization and the collection of December 1997. data were improved and extended. The number of Correspondence to: H. S. Miedema, Department of Public Health participating rheumatologists increased between 1983 and Prevention, TNO Prevention and Health, PO Box 2215, 2301 CE Leiden, The Netherlands. and 1994 from 32 to 85 (37 and 80%, respectively, of