Background Despite the availability of regular STI care by STI clinics and general practitioners many young people at high risk for Chlamydia trachomatis are hidden to care. Members of the social and sexual networks relating to Chlamydia positives typically show high risk, therefore these networks members are potentially valuable targets for interventions.

Methods Intervention Mapping (IM), a systematic approach to develop theory- and evidence-based interventions, was used to develop a strategy to target Ct testing towards young people who are currently hidden to care. Both clinical users (i.e. sexual health care nurses) and public users (i.e., young people) were closely involved in the IM process. A needs assessment study was carried out using semi-structured interviews among users (n = 21), a literature search and by taking lessons learned from existing Ct screening programmes. Theoretical methods and practical applications to reach high risk young people and influence testing were selected and translated into specific programme components.

Results The IM approach resulted in the development of a secure and web-based outreach Chlamydia trachomatis screening strategy. Ct testing and the motivation of peers were proposed as the desired behavioural outcomes. Key methods include web-based Respondent Driven Sampling (web-based RDS), starting from young Chlamydia positive sexual health care centre clients, to reach and motivate peers (i.e., sex partners and friends) to get tested. Furthermore, these sex partners and friends can also motivate peers in their networks to get tested, and so on.

Conclusions We believe this is a unique Chlamydia screening strategy that combines web-based RDS with the delivery of Chlamydia testing to high risk young people within their sexual and social networks. This approach can become an integral part in sexual health care for reaching high risk populations with Ct screening and treatment which is important for both the individual and public health level.