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Background On 1 January 2014, the minimum age to buy alcohol increased (16–18 years), accompanied by a public awareness campaign (NIX18). Decreases in alcohol consumption are associated with less risky sexual behaviour. This study analyzed the association between the health reforms andChlamydia trachomatis infections (chlamydia) among young heterosexual people. Methods Chlamydia positivity rates, age, and gender from all STI-clinic attendees between 16 and 19 years old in the Netherlands of 2010 to 2016 were obtained. Interrupted time-series assessed immediate and gradual trends in chlamydia rates. Results Among the control group (18–19 year olds) chlamydia rates increased 0.5% each post-ban month (95% Confidence Interval [CI] 1.002–1.008, p = .001). Among 16–17 year olds there was no monthly increase post-ban (Rate Ratio 1.000, 95% CI 0.993–1.007, p = .948). In terms of confounders, only controlling for partner notification dissolved these time trends. Conclusions We found that chlamydia rates after the alcohol ban differed between 16–17 year olds and 18–19 year olds. This demonstrates that the health reforms might have affected this secondary outcome, but obtaining certainty using national surveillance data is difficult. Specific studies should be designed, as now changes in chlamydia over time could be explained by STI-clinic policy changes, by changes on an individual level including reduced alcohol consumption or most likely by the combination of these factors.

Background: Chlamydia trachomatis (CT), the most common bacterial sexually transmitted infection (STI) among young women, can result in serious sequelae. Although the course of infection is often asymptomatic, CT may cause pelvic inflammatory disease (PID), leading to severe complications, such as prolonged time to pregnancy, ectopic pregnancy, and tubal factor subfertility. The risk of and risk factors for complications following CT-infection have not been assessed in a long-term prospective cohort study, the preferred design to define infections and complications adequately. Methods: In the Netherlands Chlamydia Cohort Study (NECCST), a cohort of women of reproductive age with and without a history of CT-infection is followed over a minimum of ten years to investigate (CT-related) reproductive tract complications. This study is a follow-up of the Chlamydia Screening Implementation (CSI) study, executed between 2008 and 2011 in the Netherlands. For NECCST, female CSI participants who consented to be approached for follow-up studies (n = 14,685) are invited, and prospectively followed until 2022. Four data collection moments are foreseen every two consecutive years. Questionnaire data and blood samples for CT-Immunoglobulin G (IgG) measurement are obtained as well as host DNA to determine specific genetic biomarkers related to susceptibility and severity of infection. CT-history will be based on CSI test outcomes, self-reported infections and CT-IgG presence. Information on (time to) pregnancies and the potential long-term complications (i.e. PID, ectopic pregnancy and (tubal factor) subfertility), will be acquired by questionnaires. Reported subfertility will be verified in medical registers. Occurrence of these late complications and prolonged time to pregnancy, as a proxy for reduced fertility due to a previous CT-infection, or other risk factors, will be investigated using longitudinal statistical procedures. Discussion: In the proposed study, the occurrence of late complications following CT-infection and its risk factors will be assessed. Ultimately, provided reliable risk factors and/or markers can be identified for such late complications. This will contribute to the development of a prognostic tool to estimate the risk of CT-related complications at an early time point, enabling targeted prevention and care towards women at risk for late complications. Trial registration: Dutch Trial Register NTR-5597. Retrospectively registered 14 February 2016.

Objectives Ethnic minorities (EM) from STI-endemic countries are at increased risk to acquire an STI. The objectives of this study were to investigate the difference in STI clinic consultation and positivity rates between ethnic groups, and compare findings between Dutch cities. Methods Aggregated population numbers from 2011 to 2013 of 15–44 year-old citizens of Amsterdam, Rotterdam, The Hague and Utrecht extracted from the population register (N=3 129 941 person-years) were combined with aggregated STI clinic consultation data in these cities from the national STI surveillance database (N=113 536). Using negative binomial regression analyses (adjusted for age and gender), we compared STI consultation and positivity rates between ethnic groups and cities. Results Compared with ethnic Dutch (consultation rate: 40.3/1000 person-years), EM from Eastern Europe, Sub-Sahara Africa, Suriname, the Netherlands Antilles/Aruba and Latin America had higher consultation rates (range relative risk (RR): 1.27–2.26), whereas EM from Turkey, North Africa, Asia and Western countries had lower consultation rates (range RR: 0.29–0.82). Of the consultations among ethnic Dutch, 12.2% was STI positive. Positivity rates were higher among all EM groups (range RR: 1.14–1.81). Consultation rates were highest in Amsterdam and lowest in Utrecht independent of ethnic background (range RR Amsterdam vs Utrecht: 4.30–10.30). Positivity rates differed less between cities. Conclusions There were substantial differences in STI clinic use between ethnic groups and cities in the Netherlands. Although higher positivity rates among EM suggest that these high-risk individuals reach STI clinics, it remains unknown whether their reach is optimal. Special attention should be given to EM with comparatively low consultation rates.

Infectious syphilis (syphilis) is diagnosed predominantly among men who have sex with men (MSM) in the Netherlands and is a strong indicator for sexual risk behaviour. Therefore, an increase in syphilis can be an early indicator of resurgence of other STIs, including HIV. National and worldwide outbreaks of syphilis, as well as potential changes in sexual networks were reason to explore syphilis trends and clusters in more depth. National STI/HIV surveillance data were used, containing epidemiological, behavioural and clinical data from STI clinics. We examined syphilis positivity rates stratified by HIV status and year. Additionally, we performed space-time cluster analysis on municipality level between 2007 and 2015, using SaTScan to evaluate whether or not there was a higher than expected syphilis incidence in a certain area and time period, using the maximum likelihood ratio test statistic. Among HIV-positive MSM, the syphilis positivity rate decreased between 2007 (12.3%) and 2011 (4.5%), followed by an increasing trend (2015: 8.0%). Among HIV-negative MSM, the positivity rate decreased between 2007 (2.8%) and 2011 also (1.4%) and started to increase from 2013 onwards (2015: 1.8%). In addition, we identified three geospatial clusters. The first cluster consisted of MSM sex workers in the South of the Netherlands (July 2009-September 2010, n=10, p

SUMMARYLivestock-associated MRSA has been found in various animals, livestock farmers and retail meat. This study aimed to determine the prevalence and determinants of nasal MRSA carriage in pig slaughterhouse workers. Three large pig slaughterhouses in The Netherlands were studied in 2008 using human and environmental samples. The overall prevalence of nasal MRSA carriage in employees of pig slaughterhouses was 5·6% (14/249) (95% CI 3·4–9·2) and working with live pigs was the single most important factor for being MRSA positive (OR 38·2,Pr=0·75). In conclusion, a high prevalence of nasal MRSA carriage was found in pig-slaughterhouse workers, and working with live pigs is the most important risk factor. Exact transmission routes from animals to humans remain to be elucidated in order to enable application of targeted preventive measures.

AIMS To determine the prevalence of anaemia among HIV-positive and -negative drug users, estimate the incidence of anaemia among HIV-positive drug users and study risk factors for prevalent anaemia with emphasis on HIV infection, gender and drug use behaviour. DESIGN, SETTING AND PARTICIPANTS Cross-sectional study among HIV-positive and HIV-negative drug users (n = 360) and a longitudinal study among HIV-positive drug users (n = 175, 860 visits) participating in a cohort study of drug users in Amsterdam. MEASUREMENTS Self-reported data on socio-demographics, drug use behaviour and zidovudine and protease inhibitor therapy on regular cohort visits. Laboratory determinations of haemoglobin concentration, CD4(+)-cell counts and HIV-1 RNA. FINDINGS The prevalence of anaemia was 21.1% among participating drug users according to the WHO definition. The incidence of anaemia in HIV-positive individuals was 33.0/100 person-years. The main risk factor for anaemia was high frequency of injecting drugs. A Quetelet body mass index < or = 20 and female gender were also positively and significantly related to anaemia in the cross-sectional study. In the longitudinal study among HIV-positive drug users progression of HIV infection indicated by low CD4(+)-cell count and AIDS diagnosis were predictive of anaemia. CONCLUSION The results indicate that drug users in the Amsterdam cohort study have a high prevalence of anaemia, which can be explained mainly by high frequency of injecting drugs and HIV infection progression. Reduction or cessation of injecting drug use should reduce anaemia.

Background Comparing and ranking hospitals based on health outcomes is becoming increasingly popular, although case-mix differences between hospitals and random variation are known to distort interpretation. The aim of this study was to explore whether surgical-site infection (SSI) rates are suitable for comparing hospitals, taking into account case-mix differences and random variation. Methods Data from the national surveillance network in the Netherlands, on the eight most frequently registered types of surgery for the year 2009, were used to calculate SSI rates. The variation in SSI rate between hospitals was estimated with multivariable fixed- and random-effects logistic regression models to account for random variation and case mix. ‘Rankability’ (as the reliability of ranking) of the SSI rates was calculated by relating within-hospital variation to between-hospital variation. Results Thirty-four hospitals reported on 13 629 patients, with overall SSI rates per surgical procedure varying between 0 and 15·1 per cent. Statistically significant differences in SSI rate between hospitals were found for colonic resection, caesarean section and for all operations combined. Rankability was 80 per cent for colonic resection but 0 per cent for caesarean section. Rankability was 8 per cent in all operations combined, as the differences in SSI rates were explained mainly by case mix. Conclusion When comparing SSI rates in all operations, differences between hospitals were explained by case mix. For individual types of surgery, case mix varied less between hospitals, and differences were explained largely by random variation. Although SSI rates may be used for monitoring quality improvement within hospitals, they should not be used for ranking hospitals.

This cross-sectional study among heterosexual migrant groups in south-eastern Amsterdam, the city area where the largest migrant groups live, provides an insight into HIV testing behaviour in this particular group. Participants were recruited at street locations (May 1997-July 1998) and interviewed using structured questionnaires. They also donated saliva for HIV testing. In total, 705 males and 769 females were included in this study (Afro-Surinamese (45%), Dutch-Antilleans (15%) and West Africans (40%)). Prior HIV testing was reported by 38% of all migrants (556/1479), of which only a minority (28%) had actively requested HIV testing. Multivariate logistic regression showed that not actively requesting HIV testing was more likely among younger (< 23 years) migrants, especially women (ORwomen: 4.79, p < 0.01, ORmen: 1.81, p < 0.05). Furthermore, women without previous STI treatment (OR 2.19, p < 0.05) with Afro-Surinamese ethnicity (OR 2.12, p < 0.05), men without health insurance (OR 2.17, p < 0.05) and with low education (p < 0.01) were also more likely to not actively request HIV testing. Active requests for HIV testing in case of HIV risk should be facilitated by promoting HIV testing and by improving accurate self-assessment of risk for HIV infection, especially among the groups that do not actively request HIV testing. This would increase HIV awareness and provide the opportunity of better medical care earlier in HIV infection.