Speech sound disorder or DLD (phonology)? Towards a consensus agreement on terminology

The publication of phase 2 of the CATALISE project in 2017 clarified terminology for children with developmental language disorder (DLD) or delay but unintentionally muddied the water for children with unintelligible speech. A diagnostic label of DLD (phonology) indicates poor prognosis and phonological disorder that persists into middle childhood. However, in contrast to other diagnostic labels that fall under the overarching term of speech sound disorder (SSD), DLD (phonology) does not elucidate the characteristics of the child's speech nor does it point us in the direction of appropriate intervention.

The aim of this paper is to discuss terminology in SSD leading to an evidence-based model which builds on the model of DLD developed in CATALISE, supports descriptive diagnosis and signposts intervention.

Following a focused review of literature proposing or describing terminology for SSD, an expert group of researchers in developmental SSD proposed a revised model of existing terminology. Groups of UK speech and language therapists (SLTs) who provide services for children with SSD were asked to comment on its acceptability and feasibility.

A three-level terminology model was developed. This comprised an overarching Level 1 term; Level 2 terms that differentiated SSD of unknown origin from SSD with associated or underlying conditions; and specific diagnostic terms at Level 3 to support further assessment and intervention decisions. Consulted SLTs generally expressed agreement with the proposed terminology and a willingness to adopt it in practice.

Existing terminology for childhood SSD provides a good basis for clinical decision-making. A modified version of Dodd's (2005) terminology was found to be acceptable to UK SLTs. There is an evident overlap of SSD with CATALISE terminology. However more detailed and specialist terminology than 'DLD (phonology)' is required to support clinical decision-making. It is proposed that endorsement by the UK Royal College of Speech and Language Therapists would obviate the need for a Delphi process.

What is already known on this subject Over nearly a hundred years, as our knowledge and understanding of speech sound disorder (SSD) has increased, so has the terminology that is used to describe those disorders. Current terminology not only describes subtypes of SSD but can also signpost us to effective interventions. With the publication, in 2017, of phase 2 of CATALISE a new term of 'developmental language disorder (DLD) (phonology)' was introduced with the unintentional consequence of challenging more specific descriptive terms for SSD. What this paper adds In the context of CATALISE and DLD (phonology), the history and nature of SSD terminology are reappraised. Building on the model of DLD developed in CATALISE, a tiered model that supports descriptive diagnosis and signposts intervention is proposed for discussion. Clinical implications of this study The proposed model of terminology for SSD provides descriptive and detailed labels that will support accuracy in differential diagnosis of developmental SSD by speech and language therapists. Furthermore, a decision-making tree for SSD demonstrates the pathway from diagnostic use of the terminology to the selection of evidence-based, effective interventions.