BackgroundDemand management describes any method used to monitor, direct or regulate patient referrals. Several strategies have been developed to manage the referral of patients to secondary care, with interventions targeting primary care, specialist services, or infrastructure.ObjectiveThis research aimed to conduct an inclusive systematic review and logic model synthesis in order to better understand factors impacting on the effectiveness of interventions targeting referral between primary and secondary medical health care.DesignThe approach combined systematic review with logic modelling synthesis techniques to develop an evidence-based framework of factors influencing the pathway between interventions and system-wide changes.SettingPrimary health care.Main outcome measuresReferral from primary to secondary care.Review methodsSystematic searches were undertaken to identify recent, relevant studies. Quality of individual studies was appraised, with consideration of overall strength of evidence. A narrative synthesis and logic model summary of the data was completed.ResultsFrom a database of 8327 unique papers, 290 were included in the review. The intervention studies were grouped into four categories of education interventions (n = 50); process change interventions (n = 49); system change interventions (n = 38); and patient-focused interventions (n = 3). Effectiveness was assessed variously in these papers; however, there was a gap regarding the mechanisms whereby these interventions lead to demand management impacts. The findings suggest that, although individual-level interventions may be popular, the stronger evidence relates only to peer-review and feedback interventions. Process change interventions appeared to be more effective when the change resulted in the specialist being provided with more or better quality information about the patient. System changes including the community provision of specialist services by general practitioners, outreach provision by specialists and the return of inappropriate referrals appeared to have evidence of effect. The pathway whereby interventions might lead to service-wide impact was complex, with multiple factors potentially acting as barriers or facilitators to the change process. Factors related, first, to the doctor (including knowledge, attitudes and beliefs, and previous experiences of a service), second, to the patient (including condition and social factors) and, third, to the influence of the doctor–patient relationship. We also identified a number of potentially influential factors at a local level, such as perceived waiting times and the availability of a specialist. These elements are key factors in the pathway between an intervention and intended demand management outcomes influencing both applicability and effectiveness.ConclusionsThe findings highlight the complexity of the referral process and multiple elements that will impact on intervention outcomes and applicability to a local area. Any interventions seeking to change referral practice need to address factors relating to the individual practitioner, the patient and also the situation in which the referral is taking place. These conclusions apply especially to referral management in a UK context where this whole range of factors/issues lies well within the remit of the NHS. This work highlights that intermediate outcomes are important in the referral pathway. It is recommended that researchers include measure of these intermediate outcomes in their evaluation of intervention effectiveness in order to determine where blocks to or facilitators of system-wide impact may be occurring.Study registrationThe study is registered as PROSPERO CRD42013004037.FundingThe National Institute for Health Research Health Services and Delivery Research programme.