Abstract
Randomized controlled trials (RCTs) focused on idiopathic social communication delay (SCD) in the first year of life are rare. We preliminarily tested the efficacy of an 8-week caregiver-implemented intervention for infants with idiopathic SCD. Infants (8-12 months) with SCD were block-randomized with caregivers to the Infant Achievements (IA) (n = 18) or Caregiver Education (CE) (n = 20) group in this assessor-masked RCT. Assessments were completed at baseline, post-intervention, and 8-week follow-up. IA caregivers received reflective, home-based coaching to implement naturalistic developmental behavioral intervention (NDBI) strategies. PRIMARY OUTCOMES: masked ratings of caregiver implementation fidelity, frequency of infant initiation of joint attention (IJA), and percent of coordination of joint engagement (CJE). SECONDARY OUTCOMES: masked researcher-administered and scored Mullen Scales of Early Learning (MSEL) language and Visual Reception scaled scores; nonmasked caregiver-reported Communication and Symbolic Behavior Scales Caregiver Questionnaire (CSBS CQ) Social, Speech, and Symbolic composite scores and McArthur-Bates Communication Development Inventories Words Understood and Produced scores. Prespecified analyses followed an intent-to-treat approach using Generalized Linear Mixed Models for non-normally distributed outcomes and linear mixed-effects models for those with normal distributions. Significant group by time effects favored the IA group relative to the CE group on all primary outcomes at post-intervention (p's ≤ 0.001), and for caregiver fidelity and IJA, at follow-up (≤ 0.03). Significant IA intervention effects were detected on secondary outcomes of nonverbal cognition (MSEL Visual Reception) and CSBS CQ Speech composite at post-intervention (< 0.01) and follow-up (≤ 0.02). IA equips caregivers to learn and generalize the implementation of child-responsive NDBI strategies and propels pre-linguistic social communication advances in SCD infants. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT03404505.