Background There are often gaps between what is recommended in guidelines and what health professionals do and service users receive. Implementation strategies, as distinct from EBIs, are “methods or techniques used to enhance the adoption, implementation, and sustainment of a clinical program or practice”. Although descriptions and applications of the process of tailoring implementation strategies vary, tailoring has generally been described as a prospective process for selecting and modifying strategies to address contextual determinants of implementation in an effort to increase implementation success. This review updates a Cochrane review of the effects of tailored strategies originally completed in 2005 and subsequently updated in 2010 and 2015. The 2015 review identified 32 studies and reported a small to moderate effect compared to no strategy or a non-tailored strategy Since the publication of the last revision of this review, several new studies of tailored strategies have been published. Consequently, there may be additional evidence on the effectiveness of tailoring or on how it can be undertaken most effectively. Since tailoring implementation strategies is increasingly advised as an approach for selecting and modifying strategies, we feel it important to undertake an update of this review. Objectives We will address the same two questions considered in the previous versions of the review: Are tailored strategies effective in improving professional practice? Are tailored strategies effective in improving healthcare outcomes? Search methods We will search RCTs and cluster RCTs on CENTRAL, CINAHL, Embase, MEDLINE, BNI, and grey literature sources, along with three trial registers. Selection criteria We will include studies evaluating strategies “to improve professional practice that are planned, taking account of prospectively identified determinants of practice”. The strategy must target healthcare teams or individuals. The identification of determinants must have been undertaken before the design and delivery of the strategy. Outcomes must include measures of professional practice, patient healthcare outcomes or measures of adverse effects. Data collection and analysis At least two authors will perform title and abstract screening and full texts, extract data, and assess risk of bias. We will assess effects on professional practice, patient healthcare outcomes or measures of adverse effects. We will assess heterogeneity, sensitivity, and undertake meta-analysis where appropriate. Main results Publication is anticipated Q4 2023.

Funded by a Health Research Board Research Leader award held by Sheena McHugh (HRB-RL-2020-004)