Shared characteristics of intervention techniques for oral vocabulary and speech comprehensibility in preschool children with co-occurring features of developmental language disorder and a phonological speech sound disorder: protocol for a systematic review with narrative synthesis.

INTRODUCTION: Evidence suggests that over one-third of young children with developmental language disorder (DLD) or speech sound disorder (SSD) have co-occurring features of both. A co-occurring DLD and SSD profile is associated with negative long-term outcomes relating to communication, literacy and emotional well-being. However, the best treatment approach for young children with this profile is not understood. The aim of the proposed review is to identify intervention techniques for both DLD and SSD, along with their shared characteristics. The findings will then be analysed in the context of relevant theory. This will inform the content for a new or adapted intervention for these children.

METHODS AND ANALYSIS: This search will build on a previous systematic review by Roulstone et al (2015) but with a specific focus on oral vocabulary (DLD outcome) and speech comprehensibility (SSD outcome). These outcomes were identified by parents and speech and language therapists within the prestudy stakeholder engagement work. The following databases will be searched for articles from January 2012 onwards: Ovid Emcare, MEDLINE Complete, CINAHL, APA PsycINFO, Communication Source and ERIC. Two reviewers will independently perform the title/abstract screening and the full-text screening with the exclusion criteria document being revised in an iterative process. Articles written in languages other than English will be excluded. Data will be extracted regarding key participant and intervention criteria, including technique dosage and delivery details. This information will then be pooled into a structured narrative synthesis.

ETHICS AND DISSEMINATION: Ethical approval is not needed for a systematic review protocol. Dissemination of findings will be through peer-reviewed publications, social media, and project steering group networks.

PROSPERO REGISTRATION NUMBER: CRD4202237393.