The Netherlands

THE NETHERLANDS

GENERAL PRACTICE SYSTEM

The Dutch system of health care is based on GPs who practice in the community but not in the hospital, refer-ring ambulatory patients to specialists for outpatient or inpatient care. Specialists report their findings to the GP, who acts as a gatekeeper. Approximately 90% of the patients’ presenting problems are addressed by the GP (van der Lei et al., 1993; Leufkens and Urquhart, 2005) time staff physicians who are specialists of various kinds provide hospital care. Medical care, including prescription drugs, is paid for by various insurers, which provide a basic service to all citizens. Patients can only be registered with one GP but are free to change, which happens infrequently and nearly always because the patient moves out of the area. When a patient trans-fers, so does the record. More than 75% of the patients will visit their GP at least once per year (van derLei et al., 1993). The high degree of computerization of GPs has given rise to the birth of several GP networks; most of them are connected to one of the seven University Centres. One of the largest research-oriented GP databases is the IPCI database, which has been created with the specific purpose to conduct phar-macoepidemiological studies (van der Lei et al., 1993; Vlug et al., 1999).

INTEGRATED PRIMARY CARE INFORMATION

In 1992, the IPCI Project was started by the Depart-ment of Medical Informatics of the Erasmus Univer-sity Medical School, initially in collaboration with Intercontinental Medical Statistics (IMS). In 1998, IMS stepped out, and since then the database was run independently by the department of Medical Informat-ics in collaboration with the Pharmacoepidemiology Unit. Integrated Primary Care Information is a longi-tudinal observational database that contains data from computer-based patient records of a selected group of GPs throughout the Netherlands that voluntarily chose to supply data to the database (Vlug et al., 1999). General practitioners only receive a minimal reim-bursement for their data and control usage of their data, through the Steering Committee and through the possibility to withdraw data for specific studies. The collaborating GPs are comparable to other Dutch GPs regarding age and gender.

As of January 2005, there are 120 practices belong-ing to more than 150 GPs that have provided data to the database. The first practice was recruited into the IPCI project in 1994. Practices have therefore been supply-ing data for varying periods. The database contains information on more than 700 000 patients. This is the cumulative amount of patients who have ever been part of the dynamic cohort of registered patients. Turnover occurs as patients move and transfer to new practices. The records of ‘transferred out’ patients remain on the database and are available for retrospective study with the appropriate time. As of December 2005, there were 400 000 active patients registered with the collaborat-ing GPs, 49% was male and 57% was insured through the Sickfund, and the mean age was 38 years. In 2006, the IPCI database is expected to grow to cover a popu-lation of 1 million active subjects. This is achieved by extending data retrieval to GPs with other GP informa-tion systems than the original ELIAS system alone. Data are downloaded on a monthly basis, and the information is sent to the gatekeeper who anonimizes all information before further access is provided.

The database contains anonymous patient iden-tifiers, demographics and eligibility dates (date of birth, sex, patient identification, insurance, date of registration and transferring out and date of death), notes (subjective and assessment text), symptoms, signs, prescriptions, and indications for therapy, phys-ical findings, referrals, hospitalizations and labora-tory values. All data are directly entered into a computer during the consultation hour where it is stored (see Figure 29.1 for database structure). The International Classification of Primary Care (ICPC) is the coding system for patient complaints and diag-noses, but diagnoses and complaints can also be entered as free text that is available as raw data (Lamberts and Wood, 1987). Prescription data such as product name, quantity dispensed, dosage regi-mens, strength and indication are entered into the computer to produce printed prescriptions (Vlug et al., 1999). The National Database of drugs, maintained by the Z-index, enables the coding of prescriptions, according to the Anatomical Therapeutic Chemical (ATC) classification scheme recommended by the WHO (de Smet, 1988).

Access to original medical records (discharge letters of hospitals) and administration of questionnaires to GPs is possible through the gatekeeper but only after approval of the IPCI Steering Committee. Data accu-mulated in the IPCI database have proven to be of high quality and suitable for epidemiological and pharma-coepidemiological research (Vlug et al., 1999). Data can be used for research purposes, but because of the privacy issues related to the presence of clinical notes access is possible only at the Erasmus Univer-sity Medical Centre and after approval of the Steering Committee.

The database has been used for studies on disease occurrence (Eland et al., 2001, 2002; Verhamme et al., 2002; Straus et al., 2004a; van Soest et al., 2005) and drug utilization such as the change in prescriptions of terbinafine following a highly debated press campaign (‘t Jong et al., 2004) or appropri-ate prescribing in the elderly (van der Hooft et al., 2005); adherence and persistence with treatment ranging from gastroprotection (Sturkenboom et al., 2003a,b), antihypertensives, lipid lowering drugs, antidepressants and respiratory drugs and the asso-ciation between adherence and treatment outcomes; effectiveness of drugs and vaccinations (Voordouw et al., 2003, 2004; Dieleman et al., 2005); and last but not the least, a variety of adverse drug reac-tions (Visser et al., 1996; van der Linden et al., 1998, 1999; Straus et al., 2004b, 2005). For a complete updated list of publications, we refer to the website (www.ipci.nl).

Special features of the database comprise the possi-bility to conduct randomized database studies with naturalistic follow-up (Mosis, 2005a,b), pharmacoge-netic studies and the possibility to return to patients and ask for additional information, such as reasons for non-compliance, quality of life and blood samples.