Jaarlijkse systematische chlamydiascreening*

Objective

To evaluate the effectiveness of register-based, yearly chlamydia screening.

Design

Controlled trial with randomised phased implementation (‘stepped wedge’ design) in three regions in the Netherlands, namely Amsterdam, Rotterdam and Parkstad Limburg in the province South Limburg (NTR 3071, www.trialregister.nl).

Method

From March 2008 to February 2011, postal invitations for chlamydia screening were sent annually to all young people in the 16-29 year age group registered as resident in the participating municipalities (n = 317,304 at the start of the study). In the letter they were requested to order a test kit via Internet with which they could take samples to be tested for the presence of a chlamydia infection, and then to send these samples to a participating laboratory for analysis. Communication with participants took place via Internet, email and text messaging. Treatment for any chlamydia infection was provided by the general practitioner or at the local health authority outpatients’ clinic for sexually transmitted diseases. The main outcome measures were level of participation and the percentage of positive tests for chlamydia and estimated chlamydia infection prevalence (or trends in this).

Results

The participation rate for chlamydia screening in the intervention group was 16.1% after the 1st annual invitation, 10.8% after the 2nd and 9.5% after the 3rd, compared with 13.0% in the control group, who were invited at the end of the 2nd screening round. The percentage of persons testing positive for chlamydia at the 1st invitation was the same in intervention areas as in control areas (4.3%). This percentage remained comparable (4.1%) at the 3rd invitation. The percentage of persons testing positive for chlamydia did not decrease significantly per region or socio-demographic subgroup. It was only among persons who participated three times (2.8% of all invitees) that the percentage of positive tests decreased significantly from 5.9 to 2.9% (odds ratio: 0.49; 95% CI: 0.47-0.50).

Conclusion

No significant effect could be shown of 3 years of systematic chlamydia screening on the percentage of persons with a positive chlamydia test at the experienced, low participation levels. There is currently insufficient evidence to support national implementation of this chlamydia screening.

Conflict of interest and financial support: a disclosure form provided by the author is available along with the full text of this article at www.ntvg.nl; search for A5503, click on ‘Belangenverstrengeling’ (‘Conflict of interest’).