Labelling, defining and classifying the active ingredients in oral language interventions for children with or at risk of developmental language disorder: a systematic review and qualitative synthesis

Background

In recent years, there has been an increase in studies reporting on effective child language interventions for people with or at risk for (Developmental) Language Disorder ((D)LD). However, the translation of this evidence into practice has been impeded by under-specified intervention reporting, specifically on what the active ingredients of therapy are and how they are defined. This systematic review forms part of a larger research programme conducted by the Intervention Consensus for Language Disorder group.

Aim

To identify, summarise, and synthesize how the active ingredients of oral language interventions for children with or at risk for (D)LD have been labelled, defined, described, and classified in empirical and clinical literature.

Methods

This registered review (PROSPERO ID CRD42024541407) adhered to PRISMA guidelines. Search terms were included in seven electronic databases. Included literature comprised peer-reviewed oral language intervention studies (published in English, German, Portuguese, Croatian, Italian, or Finnish; between January 2019 and May 2024; and reporting on participants who were ≤ 18 years, with/at risk for (D)LD); intervention-focused taxonomies; intervention manuals (published in the last 10 years); and textbooks used to teach child language interventions in pre-registration Speech and Language Therapy/Pathology courses (identified through the Whatworks database and a social media survey, respectively). Data extraction was guided by the TIDieR checklist with additional items deemed relevant for this review.

Results

9576 articles were identified and screened; 619 were included for full text screening; and 243 articles were included in the review. Significant reporting inconsistencies were evident, including identical labels masking different mechanisms, as well as similar mechanisms operating under different labels; conflation of discrete techniques and procedures; the application of common labels in multiple ways; the use of unfamiliar terminology to refer to familiar techniques; and the use of broad terms masking multiple active ingredients. These inconsistencies do not align with what is considered well-specified active ingredients and consequently, significantly impede intervention replication and cross study comparisons.

Conclusion

This review highlights the need to develop consensus on (1) how active ingredients of intervention are labelled and defined so that they are consistent, precise and non-overlapping and (2) a comprehensive integrative taxonomy for ease of understanding and use, when reporting on oral language interventions for children with or at risk for (D)LD.

WHAT THIS PAPER ADDS

What is already known on this subject

Oral language interventions contain numerous proposed ‘active ingredients’, but these are reported with substantial inconsistency across studies, textbooks, and intervention manuals. In addition, different taxonomies classify similar elements in divergent ways.

What this paper adds to the existing knowledge

We have provided the first comprehensive analysis demonstrating the extent of inconsistency, ambiguity, and conceptual overlap in how active ingredients are labelled and described in the oral language intervention literature. There is misalignment across current taxonomies and we lack an internationally agreed framework that integrates discrete active ingredients along with dosage and contextual active support ingredients.

What are the potential or actual clinical implications of this work?

Without clear, shared definitions of active ingredients, clinicians cannot reliably interpret research, replicate interventions, or implement evidence-based practices with fidelity. A unified internationally agreed lexicon and taxonomy would enable clinicians to understand precisely what constitutes a given technique, how it should be delivered, and what child behaviours it is intended to influence, strengthening the quality and consistency of intervention delivery.