Evaluating an early social communication intervention for young children with Down syndrome (ASCEND): results from a feasibility randomised control trial.

Background: This paper reports the results from a feasibility trial of an early parent-delivered social communication intervention for young children with Down syndrome ('ASCEND'). The intervention focuses on developing children's early social communication skills, in particular responding to shared attention. The aim was to inform the feasibility of running a full-scale trial through National Health Service (NHS) Speech and Language Therapy (SaLT) services, to assess whether the intervention is effective in improving language skills before children with Down syndrome start school.

Methods: This was a two-arm feasibility randomised controlled trial (RCT), with 1:1 randomisation stratified by trial site, comparing the intervention plus standard NHS SaLT provision with standard NHS SaLT alone. We recruited 20 children with Down syndrome aged between 11 and 36 months through 3 NHS SaLT services, 19 of whom were randomised (10 - intervention group, 9 -control group). Pre- and post-intervention and 6-month follow-up assessments included language, social communication skills, adaptive behaviour, quality of life (parents and children), parental anxiety and depression. The intervention was parent delivered with parents having access to SaLT services and the research team during the intervention. Data were collected on recruitment and retention, standard care, treatment fidelity, acceptability of the intervention by the parents and speech and language therapists, feasibility of collecting health economic measures and suitability of the primary outcome measure.

Results: The sample was sufficient for a feasibility study. The intervention (manual, support, materials) was positively received by the participating parents. Speech and language therapists also evaluated the acceptability of the intervention positively. Treatment fidelity which was measured by completion of weekly parent diaries and two adherence phone call was acceptable as 100% of the parent diaries were returned, over 90% of the parental diaries were completed correctly and 100% of adherence phone calls were completed. Retention was acceptable at 84% overall. The preliminary health economic data suggest that this intervention will be low cost. The sample size calculation suggests that 290 participants would need to be recruited, with 228 having a complete data set, for a full RCT.

Conclusion: Based on recruitment, retention and treatment fidelity, as well as the acceptability of the intervention to parents and speech and language therapists, a full-scale trial would be feasible in order to assess the effectiveness of the intervention.

Trial registration: ISRCTN13902755, registered on 25th August 2020, http://www.isrctn.com/ISRCTN13902755.