Prevalence of STI related consultations in general practice: results from the second Dutch National Survey of General Practice

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

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.

Comparison with STI/MHS figures and extrapolations

In 2001 STI/MHS-clinics recorded 38 117 first STI consultations with a total of 10 139 STI diagnoses.4^,5^,11^,12 The number of chlamydial infections, gonococcal infections, (early) syphilis, genital warts, genital herpes and urethritis (non-chlamydial and non-gonococcal) in 2001 was 3609, 1610, 308, 1479, 730 and 2253, respectively. One hundred and thirty-two HIV-infections were diagnosed.

Extrapolating data from the second Dutch Survey to the entire country suggests that annually over 97 00 persons with one (or more) STI related episode are seen in general practice: more than 61 000 with a diagnosis of an STI and almost 36 000 with questions and worries about STI or HIV (Table 1). Adding the number of consultations at STI/MHS-clinics, and assuming that approximately 10% of persons with STI related symptoms visit another provider for STI care (such as a reproductive health clinic or gynaecologist),13 it means that in total approximately 150 000 persons seek STI care annually in the Netherlands. In general practice 65% (97 000/150 000) of all STI related consultations take place. Comparing the number of major STI diagnoses, assuming also that 10% of diagnoses are made by other providers, 78% (61 595/78 907) of all STI diagnoses are made in general practice.

Summary of main findings

This general practice based nationwide study provides representative information about the number of STI related consultations in general practice in the Netherlands. A 1-year period prevalence of STIs was 38 per 10 000 persons and 23/10 000 for STI/HIV related questions. We calculated that two-thirds of all STI related consultations and more than three-quarters of all STI diagnoses in the Netherlands were made in general practice. More than half of all STI related diagnoses were made in practices in high urban areas.

There is marked heterogeneity in the STI diagnoses made in general practice compared to STI clinics. Syphilis and HIV diagnoses are much more concentrated within STI clinics and STI related syndromes like urethritis and cervicitis are more prevalent in general practice. This reflects the different epidemiological profiles of STI.14 Chlamydial infections are more dispersed throughout the country and less attached to specific risk categories.15 STI clinics attract a selected, more at-risk population, such as men who have sex with men and clients or workers in prostitution.14^,16

Strengths and limitations of the study

Our data demonstrate that indeed the GP contributes significantly to STI-control. We assume that our figures represent the lower limit. For instance, we did not include hepatitis B or Pediculus pubis. Also, re-infections during 1 year in the same person were not considered. The number of reproductive health related episodes is >10-fold higher than the number of STI related episodes. Some of these reproductive health related episodes can still be STI related, but were neither labelled nor detected as such. Reproductive health related episodes may also have been used by the GP for STI counselling.

A limitation of our study is the fact that our findings depend heavily on the quality of the registration by the GPs and the validity of our clustering into STI-episodes. Participating GPs were experienced in working with electronic medical records and with ICPC and did not differ significantly in diagnosing disease episodes from other GPs.10 Inter-doctor variation in ICPC coding of participating GPs in an audit using paper ‘vignettes’ was small and the level of agreement with external ICPC experts was on average 81%.10

The use of ICPC codes in analysing STI related consultations also needs caution. For instance episodes coded as gonorrhea (Y71), will certainly not yield all cases, as a significant proportion of GPs did not request (concordant with the guidelines at that time) microbiological confirmation of a male urethritis/discharge syndrome. Owing to this potential source of misclassification and in order to obtain a meaningful outcome we composed a cluster definition, using specific STI prescription data as well.

Comparison with existing literature

We compared our findings with a sentinel surveillance system (Continuous Morbidity Registration).17 This network is also GP based and covers a 1% representative sample of Dutch GPs and of the Dutch population. It reports weekly about selected health issues and holds records on urethritis and HIV related questions in general practice. The average number of consultations for urethritis in 2001 in this surveillance system was exactly the same as our cluster estimate. The number of consultations related to ‘questions and/or worries about HIV-AIDS’ in the sentinel surveillance system was 20 per 10 000, closely matching with our estimate of 23 per 10 000 (B25, X23, Y25). These quality checks support our impression that data derived in our manner from the database of the National Study are sufficiently robust to make comparisons.

In previous research we found that 1.2% of 9687 interviewees in a representative population sample aged >18 years reported symptoms in the past year, which they thought were suggestive of an STI (5% among 18–24 year olds).13 In total, 63% reported to have visited a GP for this, 20% a STI/MHS clinic, 8% another healthcare provider and 9% did not seek help for their symptoms.13 Extrapolating those data would mean that approximately 90 000 would have visited a GP for this reason and 30 000 a STI clinic or MHS facility. This closely mirrors the actual data we found in this study. The slight underestimation might be due to the fact that the questionnaire study was restricted to 18 years and older, and the questionnaire referred to healthcare seeking behaviour among those who ‘had any signs, symptoms or complaints in the past year of which you thought were suggestive for STI’.

Implications for future research or clinical practice

Our study renders support to the statement that sentinel surveillance in primary care as well as the use of data routinely registered primarily for care purposes are valuable and much less costly tools for monitoring compared to large population-based research. Accelerated access to electronic databases creates opportunities to analyse regional and local data. These might differ substantially within and between regions and cities due to different epidemiological profiles, but also due to a doctor or practice professional variation. As 90% of Dutch GPs have a computerised practice, practice data can be used in the near future for sentinel surveillance and also as a tool for quality assurance. Laboratory databases can also contribute to measure diagnostic activity in primary care if denominator data are available and can be disaggregated from other clinical and public health settings.18

Another important observation is the fact that GPs have reproductive health related consultations on a daily basis and have, on average, two new starters on oral contraceptives every month. These encounters provide avenues for tailored prevention advice and problem-oriented counselling for safer sex. Active case finding of chlamydial infection in youngsters is another contribution of the GP in STI-control. These additional tasks in primary and secondary prevention are now incorporated in the recently revised Dutch GP guideline on STI care.19 As GPs in urban and deprived areas see comparatively more STIs they should especially be targeted for continuous education programmes.

In conclusion, the GP is an important player in STI control in the Netherlands and cover two-thirds of all STI related consultations and 78% of all STIs diagnoses. Many sexual and reproductive health encounters in primary care incorporate opportunities for counselling on safer sex. Appropriate attention for sexual health in general practice is required.