Background Long-standing randomised controlled trial (RCT) evidence indicates that asthma action plans can improve patient outcomes. Internationally, however, these plans are seldom issued by professionals or used by patients/carers. To understand how the benefits of such plans might be realised clinically, we previously investigated barriers and facilitators to their implementation in a systematic review of relevant RCTs and synthesised qualitative studies exploring professional and patient/carer views. Our final step was to integrate these two separate studies. Methods First, a theoretical model of action plan implementation was proposed, derived from our synthesis of 19 qualitative studies, identifying elements which, if incorporated into future interventions, could promote their use. Second, 14 RCTs included in the quantitative synthesis were re-analysed to assess the extent to which these elements were present within their interventions (that is, ‘strong’, ‘weak’ or ‘no’ presence) and with what effect. Matrices charted each element’s presence and strength, facilitating analysis of element presence and action plan implementation. Results Four elements (professional education, patient/carer education, (patient/carer and professional) partnership working and communication) were identified in our model as likely to promote asthma plan use. Thirteen interventions reporting increased action plan implementation contained all four elements, with two or more strongly present. One intervention reporting no effect on action plan implementation contained only weakly present elements. Intervention effectiveness was reported using a narrow range of criteria which did not fully reflect the four elements. For example, no study assessed whether jointly developed action plans increased use. Whilst important from the professional and patient/carer perspectives, the integral role of these elements in intervention delivery and their effect on study outcomes was under-acknowledged in these RCTs. Conclusions Our novel approach provides an evidence-base for future action plan interventions. Such interventions need to ensure all elements in our implementation model (patient/carer and professional education to support development of effective partnership working and communication) are strongly present within them and a wider range of criteria better reflecting the realities of clinical practice and living with asthma are used to measure their effectiveness. We now intend to test such a complex intervention using a cluster trial design.