Dutch National Survey of General Practice
The study described here took place within the framework of the second Dutch National Survey of General Practice carried out by NIVEL (National Institute for Research in Primary Care), in 2001 in cooperation with the National Information Network of General Practice. The first national survey was conducted in 1987. The aim of these large National Surveys was to obtain information on the role and position of general practice in Dutch health care.9,10 In this second National Survey data were collected about health and healthcare related behaviour of 375 899 persons, registered in 104 practices with 195 GPs. Population, practices and GPs were representative for the Dutch population, with a slight under representation of single-handed GPs. Study design, methods and response will be summarised here and have been published elsewhere in more detail.9
How this fits in
Prevalence of STI-related consultations in primary care is unknown. This research demonstrates that GPs cover approximately two-thirds of all STI related consultations and three-quarters of all STI diagnosis in the Netherlands.
Sexually transmitted infections
During a 1-year period, data about all patient contacts, including information on diagnoses, referrals and prescriptions, were registered by participating GPs in electronic medical records. Diagnoses were coded according to the ICPC (International Classification of Primary Care).
Consultations dealing with the same health problem were grouped into disease episodes. The disease episode was coded with the diagnosis made in the chronologically last contact. For example, a patient diagnosed and treated with urethral discharge at his first contact (ICPC code Y03) could return 1 week later for microbiological results showing a gonococcal infection (ICPC code Y71). The episode diagnoses would be then Y71.
A patient ‘worried about HIV’ (ICPC code B90) with a negative test at follow up would remain diagnosed as an B90 episode.
Prevalence was defined as the number of persons with one or more episodes during that year (1-year period prevalence).
The database was searched for relevant ICPC codes for STIs. Some STIs do not have a unique ICPC-code. Chlamydial infection in men is coded as ‘other male genital diseases’ (Y99). Searching on Y99 would yield also non-STI related ‘other male genital diseases’ like torsion of the testis or spermatocele.
In order to make the category ‘other male genital diseases’ (Y99) relevant for our study objective, we linked it with prescription data and only retrieved those Y99 episodes for which specific STI-medication, according to the guideline in 2001, was given (azithromycine [1 g]; doxycycline [200 mg] for 7 days; and/or ciprofloxacin [500 mg]). The cluster ‘urethritis in man’ was defined as all those men who had either an episode of gonorrhea (Y71), penile discharge (Y03), urethritis not specific (U72) or ‘other male genital diseases’ for which STI-medication was given (Y99 with medication). Also epididymitis (Y74), at a young age, often a complication of STI, was restricted to those episodes for which STI-medication was given.
For women, a non-specific ICPC code for chlamydial infection exists. The GP can either categorise a chlamydial infection in females under sub-codes: cervicitis (X84), vaginitis (X85) or ‘other female genital diseases’ (X99). We defined the cluster ‘cervico-vaginitis’ as all women who had an episode of either gonorrhea (X71), cervicitis (X84) for which specific STI-medication was given, vaginitis (X85) for which STI-medication was given, or ‘other genital diseases’ (X99) for which STI-medication was given.
Pelvic inflammatory disease, a complication of STI in women, has a unique ICPC-code (X74).
Non-STI related reproductive health episodes, including contraceptive encounters, were inventarised to quantify potential prevention opportunities for tailored counselling.
Analysis
For the present analysis all STI related disease episodes were extracted from the database together with demographic information of the practices. Urban–rural classification of the practice was related to the Area Address Density according to Statistics Netherlands (www.cbs.nl): very highly urban (>2500 addresses/km2); highly urban (1500–2500 addresses/km2); moderate urban (500–1500 addresses/km2) and rural (<500 addresses/km2).
Deprived areas were defined according to existing health insurance categories, and related to low income and multiethnic neighbourhoods. According to these categories 5% of the Netherlands population lives in a deprived area.
As some people moved in or out the GP practices during the year studied we used the mid-time population as the denominator.
For extrapolation to the national level and GP practice level the 2001 population data of Statistics Netherlands (www.cbs.nl) were used (15.9 million inhabitants and a mean of 2350 persons registered in a Dutch general practice).
For comparisons with persons seen at STI clinics and MHS facilities, surveillance data from 2001 were used.