INICIACIÓN A LA ACTIVIDAD EMPRENDEDORA Y EMPRESARIAL 3º ESO

The most often quoted prevalence figure for DLD is 7.4% (Tomblin et al., 1997). It is based on a threshold of -1.25 SD and below on at least two out of five language measures and a nonverbal ability score above -1 SD. It seems obvious that different selection criteria will impact prevalence and the profiles of the children recruited. However, few studies have actually assessed in what way. One recent UK study formally tested the impact of different selection criteria (including those from Tomblin’s study) on both prevalence and functional

outcomes of DLD. Norbury et al. (2016) assessed the language of 529 children in kindergarten on a set of five language composite scores (vocabulary, grammar, narrative, expressive and receptive scores) and nonverbal performance (block design and matrices) in their first year of primary education. They also collected information about emotional functioning using the Strength and Difficulties questionnaire (Goodman, 2006), and academic attainment using the UK Early Years Foundation Stage Profile (EYFSP). “Good level” on the EYFS meant children achieved UK targets on 12 areas of the curriculum. Using their sample of 529 children, stratified by age group, as the norm-reference, and selection criteria of -1.5 SD and below on two out of the five language composites and -2 SD and above on nonverbal ability, the authors reported a DLD prevalence of 7.58%. When the threshold of Tomblin’s study was applied for language measures (-1.25 SD), this figure increased to 11.11%. Of the children identified, only 11.80% reached the expected level on the EYFS. Crucially, whether they met Tomblin’s nonverbal ability criterion (above -1 SD) or not, the children identified were at risk of academic failure and emotional functioning difficulties. The application of more stringent criteria, such as the ICD-10 threshold of -2 SD on two out of five language measures and a nonverbal ability above -1 SD, led to even more important functional difficulties (no child reaching the expected EYFS level), but also much lower prevalence rates (1.07%). Table 3-1 presents an overview of these results.

Table 3-1: Results from the DLD prevalence study of Norbury et al. (2016), evaluating the impact of different recruitment criteria on prevalence and functional impact

Prevalence in Norbury et al.’s (2016) sample

Functional impact: Children achieving ‘good level’ on EYFSP Language disorder of unknown

origin (total) 1 If NVP score between 0 and -1 SD If NVP score between -1 and -2 SD 7.58% 4.80% 2.78% 11.80% 9.00% 16.62% ‘Specific Language Impairment’

(Tomblin et al., 1997 criteria) 2

7.74% 27.60%

‘Developmental Language Disorder’ (ICD-10 criteria) 3

NVP: Non-verbal performance. EYFSP: Early Years Foundation Stage Profile. 1 _{DSM‐5 criteria: Language scores}

−1.5 SD or more below normative mean on 2/5 language composite scores. No known medical diagnosis. 2

Tomblin et al. (1997) criteria: Language scores −1.25 SD or more below normative mean on 2/5 language composite scores. NVIQ > -1 SD. No known medical diagnosis. Note: inclusion of children with NVIQ > -2 SD increases prevalence estimate to 11.11%. 3 _{ICD-10 criteria: Language scores −2 SD or more below normative mean}

on 2/5 language composite scores; NVIQ > -1 SD, and no known medical diagnosis. Note this creates a significant (1 SD) discrepancy between verbal and nonverbal ability.

Inclusion criteria need to be balanced to account for both severity of language difficulties (as attested by language scores) and their functional impact. As suggested above, even milder language difficulties (-1.25 SD and below on language scores) may have functional impact. Similarly, nonverbal scores just above the threshold for intellectual disability (-2 SD) produce similar functional outcomes to those of more stringent criteria used in previous studies of DLD (-1 SD). There is thus no evidence to support cognitive referencing or highly stringent language thresholds in studies interested in the literacy or academic skills of children with DLD. Another important finding of Norbury and colleagues pertains to the mismatch between their identification and referral to school support or professional services. Less than half of the children they identified as having DLD were receiving extra support either at school or in speech and language therapy services, suggesting their needs had not been prioritised in their educational context. Recent evidence suggests that this lack of recognition of language needs in the UK education system may continue -and accentuate- until the end of primary school (Dockrell & Hurry, 2018).

To our knowledge, no diagnostic or prevalence studies of DLD have been conducted in the French context, and no statutory consensus could be found, that reflected either the new DSM-5, or the recent debates over diagnostic criteria in language disorders. In fact, according to statutory documents, the diagnostic criteria that prevails in French speech and language therapy practice still distinguishes between “dysphasies”, which ties in with the conservative ICD-10 definition of language disorders and involves cognitive referencing and language scores at the very extreme end of the distribution (-2 SD), and other language and communication delays and disorders of unknown origins, whose diagnosis is made on the basis of the functional complaint and language scores (JO du 13/06/18, 2018, sec. TITRE IV-

CHAPITRE II-Article 2-Rééducation des troubles de la voix, de la parole, la communication et du langage). Because of the potential mismatches between current recognition and actual language needs on the one hand, and between the definition of language needs in the French and English contexts on the other hand, it was necessary to define a set of uniform criteria for the identification of DLD in the current study. They are informed by the evidence gathered in the present section and will be detailed in section 6.2.1 of the methods chapter.