Data Resource Profile: The Danish National Prescription Registry

Abstract

Denmark has a long tradition of creating nationwide administrative and health registries.1,2 Examples include its registries on causes of death,3 hospitalizations4 and cancer,5 and on socioeconomic parameters such as income6 and education.7 A registry central to Danish pharmacoepidemiology is the Register of Medicinal Product Statistics, established in 1994. This registry includes data on all drugs sold in primary care or purchased for use in Danish hospitals. Whereas aggregate data on gross sales of drugs are freely available online [www.medstat.dk],8 individual-level data on prescriptions filled by Danish residents at community pharmacies are available as an independent sub-registry—the National Prescription Registry (NPR).9 NPR data have been available to researchers through Statistics Denmark since 2003, and more recently also through the Danish Health Data Authority. Given these recent changes in data access and the need to evaluate the Registry’s strengths and limitations, this data resource profile provides a review of the NPR, with emphasis on its role in research. The Danish National Health Service10 provides universal tax-supported healthcare, guaranteeing all Danish residents free access to general practitioners (GPs) and hospitals. GPs are the cornerstone of the Danish healthcare system, providing health care free at the point of delivery and acting as gatekeepers for specialist care. GPs often resume the responsibility for treatment after a diagnosis has been established by a specialist. Therefore, GPs issue \most prescriptions in Denmark.11 Patient co-payments are required for prescription drugs. A central authority (the Reimbursement Committee) decides whether a particular medicine is reimbursable, and all reimbursable medicines are covered by a tax-financed drug reimbursement scheme. According to this scheme, the percentage of reimbursed costs increases with an individual’s total expenditures for reimbursable medicines during the most recent 365 days.12 At present, the first 130€ is paid in full by the patient (except for children, who immediately receive a 60% reimbursement). Then, reimbursements cover increasing percentages of costs, in steps of 50%, 75% and 85%, until out-of-pocket expenditures are capped at about 500€.13 All residents are automatically covered by the reimbursement scheme. The Danish community pharmacy sector consists of 314 large pharmacies, on average covering about 17 000 residents and serving about 600 customers per day. Pharmacies are privately operated, but subject to state regulation. The Danish Ministry of Health and the Danish Medicines Agency control the sector through a licensing system, which determines the number of pharmacies and their location. Although patients are not obliged to use a single pharmacy, they generally are loyal to their preferred pharmacy.11 Prescription drugs are mainly dispensed in their original packs. No upper limit exists for the amount of drug that can be dispensed at any one time. However, when medical treatment is stable, patients typically receive a 3-month supply (corresponding to packages of 100 tablets for drugs used once daily).14 About 62 000 Danish residents, mostly elderly, receive their drugs as dose-dispensed medications with a 14-day supply period.15 Since 1995, the NPR has recorded detailed information on prescriptions redeemed in Denmark. Drugs prescribed to nursing-home residents are also included. Prescriptions for children were issued under the name of the mother until 1996, and then under the child’s name. There are three notable instances when drugs are not filled at community pharmacies and thus are not captured by the registry: (i) drugs used during hospital admissions; (ii) drugs used by certain institutionalized individuals (typically due to psychiatric illnesses); and (iii) drugs supplied directly by hospitals or treatment centres (e.g. chemotherapeutic agents, immunosuppressant drugs and methadone for substance abusers). The NPR receives data recorded in the electronic dispensing systems of community pharmacies. The Registry contains 46 variables that characterize each redeemed prescription, including those describing the patient, the drug dispensed, the health provider issuing the prescription and the dispensing pharmacy. An overview of the main variables is provided in Table 1 Key variables included in the Danish National Prescription Registry *Within Statistics Denmark, these variables are included directly in the registry, whereas at the Danish Health Data Authorities they are obtained via linkage with the product code. Key variables included in the Danish National Prescription Registry *Within Statistics Denmark, these variables are included directly in the registry, whereas at the Danish Health Data Authorities they are obtained via linkage with the product code. The core variables are the Civil Personal Register (CPR) number (a unique personal identifier used in all Danish registries), the dispensing d