Netherlands Heart Foundation
Incidence and prognosis of myocardial infarction in the Netherlands based on a national record, linkage study combining different registers K There is no national registry in the Netherlands of the number of patients newly diagnosed with a cardiovascular disease, as such information on prognosis is lirnited to smaller cohort studies. Until a few years ago, we had to depend on extrapolation ofdata from cross-section and small-scale cohort studies. The Netherlands Heart Foundation (NHF), particularly the NHF Task Force 'Figures and facts on cardiovascular disease in the Netherlands', devoted itself to making such data available on a national level. First, the Foundation concluded a collaboration agreement with Prismant and the CBS (Statistics Netherlands). The legal and privacy aspects of such a project were investigated. This ultimately led to a project where linkage of data from the Dutch national hospital discharge registry (in Dutch: LMR) to the causes-of-death statistics from the CBS was performed to allow further statistical analysis of the linked files. One of the difficulties was that in the Netherlands patients are not identifiable in the LMR by a personal identification number. However, it is possible to trace records from one person by comparison of a number of identifying variables such as gender, date ofbirth and the four digits of the postal code between records. To be better able to follow patients within and between registries, a link was made between data from the Dutch population register (Gemeentelijke Basisadministratie, GBA). Based on the identifying variables, it is possible to follow people who move and change postal code. A feasibility study revealed that it was technically possible to link three files, which would trace 84% of patients being admitted to hospital for the first time for a myocardial infarction registered in the LMR to be uniquely identified in the population register.'13 For 11% ofthe patients registered in the LMR, there were associations with several individuals in the population register (administrative twins). For 5%, no corresponding population statistics records were found. These might be foreigners visiting the Netherlands.
First results of the medical record linkage The first results of linkage of data on occurrence offirst acute myocardial infarction have since been published.46 In 2000, 19,058 people were admitted to hospital for the first time for an acute myocardial infarction. Also in that year, 12,719 people died of an acute myocardial infarction outside a hospital. In total, 31,777 people suffered a myocardial infarction, fatal or nonfatal. These figures are based on a percentage of unique links for 87% of the first hospital admissions and 92% of deaths outside a hospital. Raising these results to 100% (same rates for disease and mortality applied to administrative duplicates and one-time visitors to the Netherlands) produces 432
an estimate of the total number of people with a (first) acute myocardial infarction in the Netherlands from roughly 32,000 to a maximum of 36,000 (incidence).
The results are published in the reports 'Cardiovascular disease in the Netherlands: figures and facts'.45 In 1999, Dr Hans Reitsma (Academic Medical Centre, Amsterdam) was the first researcher to receive a doctoral degree for studies on this topic.3 On 11 November 2005, PhD student Dineke Koek (Julius Centre, University Medical Centre, Utrecht) will defend her thesis entitled 'Acute myocardial infarction: linkage of national registries' on the medical record linkage project, dealing with the incidence and prognosis of the acute myocardial infarction.6 The project will be continued by PhD student Mariette Jager (Julius Centre, UMC Utrecht) who wil analyse the data on the incidence and prognosis ofstroke. These activities are conducted under the expert supervision of Dr Michiel Bots, associate Professor ofEpidemiology at the Julius Centre for Health Sciences and Primary Care (UMC, Utrecht). The NHF Task Force 'Figures and facts on cardiovascular disease in the Netherlands' is chaired by Professor Ron Peters, MD (cardiologist in the AMC in Amsterdam). i Acknowledgement With thanks to Prismant, the CBS and the members of the NHF Task Force 'Figures and facts on cardiovascular disease in the Netherlands'. Ineke van Dis, coordinator of the NHF Task Force References 1
2
3 4 5
6
Het herkennen van ziekenhuisopnamen en overlijden in cohort-onderzoek via landelijke registraties. Een samenwerkingsproject van: Centraal Bureau voor de Statistiek, Prismant en Afdeling Klinische Epidemiologie & Biostatistiek van het AMC. 2001. Reitsma JB, Kardaun JWPF, Gevers E, de Bruin A, van der Wal J, Bonsel GJ. Mogeijkheden voor anoniem follow-uponderzoek van patienten in landeijke medische registraties met behulp van de Gemeentelijke Basisadministratie: een pilotonderzoek. Ned Tijdschr Geneeskd 2003;46:2286-90. Reitsma JB. Registers in cardiovascular epidemiology [thesis]. 1999. Koek HL, van Leest LATM, Verschuren WMM, Bots ML. Hart- en vaatziekten in Nederland 2004, cijfers over leefstijl- en risicofactoren, ziekte en sterfte. Den Haag: Nederlandse Hartstichting, 2004. Koek HL, de Bruin A, Gast A, Gevers E, Kardaun JWPF, Reitsma JB, et al. Heropnamen gedurende vijfjaar na een eerste ziekenhuisopname wegens het hartinfarct. In: Van Leest LATM, Van Dis SJ, Peters RJG, Bots ML. Hart- en vaatziekten in Nederland 2005, cijfers over risicofactoren, ziekte, behandeling en sterfte. Den Haag: Nederlandse Hartstichting, 2005:65-89. Koek HL. Acute myocardial infarction: linkage ofnational registers [thesis]. 2005.
Netherlands Heart Journal, Volume 13, Number 11, November 2005
q(F
Incidence and prognosis of myocardial infarction in the Netherlands based on a national record, linkage study combining different registers K There is no national registry in the Netherlands of the number of patients newly diagnosed with a cardiovascular disease, as such information on prognosis is lirnited to smaller cohort studies. Until a few years ago, we had to depend on extrapolation ofdata from cross-section and small-scale cohort studies. The Netherlands Heart Foundation (NHF), particularly the NHF Task Force 'Figures and facts on cardiovascular disease in the Netherlands', devoted itself to making such data available on a national level. First, the Foundation concluded a collaboration agreement with Prismant and the CBS (Statistics Netherlands). The legal and privacy aspects of such a project were investigated. This ultimately led to a project where linkage of data from the Dutch national hospital discharge registry (in Dutch: LMR) to the causes-of-death statistics from the CBS was performed to allow further statistical analysis of the linked files. One of the difficulties was that in the Netherlands patients are not identifiable in the LMR by a personal identification number. However, it is possible to trace records from one person by comparison of a number of identifying variables such as gender, date ofbirth and the four digits of the postal code between records. To be better able to follow patients within and between registries, a link was made between data from the Dutch population register (Gemeentelijke Basisadministratie, GBA). Based on the identifying variables, it is possible to follow people who move and change postal code. A feasibility study revealed that it was technically possible to link three files, which would trace 84% of patients being admitted to hospital for the first time for a myocardial infarction registered in the LMR to be uniquely identified in the population register.'13 For 11% ofthe patients registered in the LMR, there were associations with several individuals in the population register (administrative twins). For 5%, no corresponding population statistics records were found. These might be foreigners visiting the Netherlands.
First results of the medical record linkage The first results of linkage of data on occurrence offirst acute myocardial infarction have since been published.46 In 2000, 19,058 people were admitted to hospital for the first time for an acute myocardial infarction. Also in that year, 12,719 people died of an acute myocardial infarction outside a hospital. In total, 31,777 people suffered a myocardial infarction, fatal or nonfatal. These figures are based on a percentage of unique links for 87% of the first hospital admissions and 92% of deaths outside a hospital. Raising these results to 100% (same rates for disease and mortality applied to administrative duplicates and one-time visitors to the Netherlands) produces 432
an estimate of the total number of people with a (first) acute myocardial infarction in the Netherlands from roughly 32,000 to a maximum of 36,000 (incidence).
The results are published in the reports 'Cardiovascular disease in the Netherlands: figures and facts'.45 In 1999, Dr Hans Reitsma (Academic Medical Centre, Amsterdam) was the first researcher to receive a doctoral degree for studies on this topic.3 On 11 November 2005, PhD student Dineke Koek (Julius Centre, University Medical Centre, Utrecht) will defend her thesis entitled 'Acute myocardial infarction: linkage of national registries' on the medical record linkage project, dealing with the incidence and prognosis of the acute myocardial infarction.6 The project will be continued by PhD student Mariette Jager (Julius Centre, UMC Utrecht) who wil analyse the data on the incidence and prognosis ofstroke. These activities are conducted under the expert supervision of Dr Michiel Bots, associate Professor ofEpidemiology at the Julius Centre for Health Sciences and Primary Care (UMC, Utrecht). The NHF Task Force 'Figures and facts on cardiovascular disease in the Netherlands' is chaired by Professor Ron Peters, MD (cardiologist in the AMC in Amsterdam). i Acknowledgement With thanks to Prismant, the CBS and the members of the NHF Task Force 'Figures and facts on cardiovascular disease in the Netherlands'. Ineke van Dis, coordinator of the NHF Task Force References 1
2
3 4 5
6
Het herkennen van ziekenhuisopnamen en overlijden in cohort-onderzoek via landelijke registraties. Een samenwerkingsproject van: Centraal Bureau voor de Statistiek, Prismant en Afdeling Klinische Epidemiologie & Biostatistiek van het AMC. 2001. Reitsma JB, Kardaun JWPF, Gevers E, de Bruin A, van der Wal J, Bonsel GJ. Mogeijkheden voor anoniem follow-uponderzoek van patienten in landeijke medische registraties met behulp van de Gemeentelijke Basisadministratie: een pilotonderzoek. Ned Tijdschr Geneeskd 2003;46:2286-90. Reitsma JB. Registers in cardiovascular epidemiology [thesis]. 1999. Koek HL, van Leest LATM, Verschuren WMM, Bots ML. Hart- en vaatziekten in Nederland 2004, cijfers over leefstijl- en risicofactoren, ziekte en sterfte. Den Haag: Nederlandse Hartstichting, 2004. Koek HL, de Bruin A, Gast A, Gevers E, Kardaun JWPF, Reitsma JB, et al. Heropnamen gedurende vijfjaar na een eerste ziekenhuisopname wegens het hartinfarct. In: Van Leest LATM, Van Dis SJ, Peters RJG, Bots ML. Hart- en vaatziekten in Nederland 2005, cijfers over risicofactoren, ziekte, behandeling en sterfte. Den Haag: Nederlandse Hartstichting, 2005:65-89. Koek HL. Acute myocardial infarction: linkage ofnational registers [thesis]. 2005.
Netherlands Heart Journal, Volume 13, Number 11, November 2005
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