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

ObjectivesTo descriptively compare and contrast intervention techniques for preschool children with features of developmental language disorder (outcome: oral vocabulary) and speech sound disorder (outcome: speech comprehensibility) and analyse them in relation to effectiveness and theory.DesignThis is a systematic review with narrative synthesis. The process was supported by an expert steering group consisting of relevant professionals and people with lived experience.Data sourcesOvid Emcare, MEDLINE Complete, CINAHL, APA PsycINFO, ERIC, and Communication Source from January 2012 were searched. Relevant studies were obtained from an initial published review (up to January 2012).Eligibility criteriaInterventions for preschool children (80% aged 2:0–5:11 years) with idiopathic speech or language needs; outcomes relating to either oral vocabulary or speech comprehensibility.Data extraction and synthesisSearches were conducted on 27 January 2023. Two independent researchers screened at abstract and full-text levels. Data regarding intervention content (eg, techniques) and format/delivery (eg, dosage, location) were extracted. Data were synthesised narratively according to the methods of Campbell et al.Results24 studies were included: 18 for oral vocabulary and 6 for speech comprehensibility. There were 11 randomised controlled trials, 2 cohort studies and 11 case series. Similarities included a focus on input-related techniques and similar therapy activities. Speech studies were more likely to be professional-led and clinic-led, rather than at home and through a parent. Analysis was restricted by heterogeneity in study design and terminology, as well as gaps within intervention reporting. Information deemed important to the expert steering group was missing.ConclusionsSimilarities and differences between intervention techniques for oral vocabulary and speech comprehensibility have been identified and synthesised. However, analysis of effectiveness was limited due to issues with study design and heterogeneity within studies. This has implications for the progression of the evidence base within the field.PROSPERO registration numberCRD42022373931.