Abstract
BackgroundA selective, systematic, Internet-based, Chlamydia Screening Implementation for 16 to 29-year-old residents started in three regions in the Netherlands in April 2008: in the cities of Amsterdam and Rotterdam and a more rural region, South Limburg. This paper describes the evaluation design and discusses the implications of the findings from the first screening round for the analysis. The evaluation aims to determine the effects of screening on the population prevalence of Chlamydia trachomatis after multiple screening rounds.MethodsA phased implementation or 'stepped wedge design' was applied by grouping neighbourhoods (hereafter: clusters) into three random, risk-stratified blocks (A, B and C) to allow for impact analyses over time and comparison of prevalences before and after one or two screening rounds. Repeated simulation of pre- and postscreening Chlamydia prevalences was used to predict the minimum detectable decline in prevalence. Real participation and positivity rates per region, block, and risk stratum (high, medium, and low community risk) from the 1st year of screening were used to substantiate predictions.ResultsThe results of the 1st year show an overall participation rate of 16% of 261,025 invitees and a positivity rate of 4.2%, with significant differences between regions and blocks. Prediction by simulation methods adjusted with the first-round results indicate that the effect of screening (minimal detectable difference in prevalence) may reach significance levels only if at least a 15% decrease in the Chlamydia positivity rate in the cities and a 25% decrease in the rural region after screening can be reached, and pre- and postscreening differences between blocks need to be larger.ConclusionsWith the current participation rates, the minimal detectable decline of Chlamydia prevalence may reach our defined significance levels at the regional level after the second screening round, but will probably not be significant between blocks of the stepped wedge design. Evaluation will also include other aspects and prediction models to obtain rational advice about future Chlamydia screening in the Netherlands.
Highlights
A selective, systematic, Internet-based, Chlamydia Screening Implementation for 16 to 29-year-old residents started in three regions in the Netherlands in April 2008: in the cities of Amsterdam and Rotterdam and a more rural region, South Limburg
Chlamydia screening in the Netherlands During 2002 and 2003 a pilot Chlamydia screening program was undertaken in the Netherlands (Pilot Ct) which showed a relatively high Chlamydia prevalence, especially in highly urbanized regions [7]
The set-up of the current screening programme facilitates the in-depth evaluation necessary to decide whether and how a national roll-out of Chlamydia screening in the Netherlands can take place in the future
Summary
A selective, systematic, Internet-based, Chlamydia Screening Implementation for 16 to 29-year-old residents started in three regions in the Netherlands in April 2008: in the cities of Amsterdam and Rotterdam and a more rural region, South Limburg. A Chlamydia screening programme for 16 to 29-year-old residents started in Amsterdam, Rotterdam, and South Limburg in April 2008. This is the first large-scale intervention that pilots a selective, systematic, Internet-based, Chlamydia screening, and it provides a unique opportunity to gather evidence of the effectiveness of screening. We clarify the design of our evaluation and discuss the implications of the results of the first round for the final evaluation after completion of two screening rounds
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