Exploring why a complex intervention piloted in general practices did not result in an increase in chlamydia screening and diagnosis: a qualitative evaluation using the fidelity of implementation model.

Not adhering to the exact intervention model may explain the lack of significant increases in chlamydia screening. To increase fidelity of implementation outside of Randomised Controlled Trial (RCT) conditions, and consequently, improve likelihood of increased screening, future public health interventions in general practices need to have: more specific action planning within the educational workshop; computer prompts added to systems and used; all staff attending the workshop; and on-going practice staff support with feedback of progress on screening and diagnosis rates fed back to all staff.