Abstract: This review includes two RCTs (154 children aged 32 months to 11 years) of communication interventions for ASD in minimally verbal children compared with a control group (treatment as usual). One RCT used a verbally based intervention (focused playtime intervention; FPI) administered by parents in the home, whereas the other used an alternative and augmentative communication (AAC) intervention (Picture Exchange Communication System; PECS) administered by teachers in a school setting. The FPI study took place in the USA and included 70 participants (64 boys) aged 32 to 82 months who were minimally verbal and had received a diagnosis of ASD. This intervention focused on developing coordinated toy play between child and parent. Participants received 12 in-home parent training sessions for 90 minutes per session for 12 weeks, and they were also invited to attend parent advocacy coaching sessions. This study was funded by the National Institute of Child Health and Human Development, the MIND Institute Research Program and a Professional Staff Congress-City University of New York grant. The PECS study included 84 minimally verbal participants (73 boys) aged 4 to 11 years who had a formal diagnosis of ASD and who were not using PECS beyond phase 1 at baseline. All children attended autism-specific classes or units, and most classes had a child to adult ratio of 2:1. Teachers and parents received PECS training (two-day workshop). PECS consultants also conducted six half-day consultations with each class once per month over five months. This study took place in the UK and was funded by the Three Guineas Trust. Both included studies had high or unclear risk of bias in at least four of the seven 'Risk of bias' categories, with a lack of blinding for participants and personnel being the most problematic area. Using the GRADE approach, we rated the overall quality of the evidence as very low due to risk of bias, imprecision (small sample sizes and wide confidence intervals) and because there was only one trial identified per type of intervention (i.e. verbally based or AAC). Both studies focused primarily on communication outcomes (verbal and non-verbal). One of the studies also collected information on social communication. The FPI study found no significant improvement in spoken communication, measured using the expressive language domain of the Mullen Scale of Early Learning expressive language, at postintervention. However, this study found that children with lower expressive language at baseline (less than 11.3 months age-equivalent) improved more than children with better expressive language and that the intervention produced expressive language gains in some children. The PECS study found that children enrolled in the AAC intervention were significantly more likely to use verbal initiations and PECS symbols immediately postintervention; however, gains were not maintained 10 months later. There was no evidence that AAC improved frequency of speech, verbal expressive vocabulary or children's social communication or pragmatic language immediately postintervention. Overall, neither of the interventions (PECS or FPI) resulted in maintained improvements in spoken or non-verbal communication in most children. Neither study collected information on adverse events, other communication skills, quality of life or behavioural outcomes. There is limited evidence that verbally based and ACC interventions improve spoken and non-verbal communication in minimally verbal children with ASD. A substantial number of studies have investigated communication interventions for minimally verbal children with ASD, yet only two studies met inclusion criteria for this review, and we considered the overall quality of the evidence to be very low. In the study that used an AAC intervention, there were significant gains in frequency of PECS use and verbal and non-verbal initiations, but not in expressive vocabulary or social communication immediately postintervention. In the study that investigated a verbally based intervention, there were no significant gains in expressive language postintervention, but children with lower expressive language at the beginning of the study improved more than those with better expressive language at baseline. Neither study investigated adverse events, other communication skills, quality of life or behavioural outcomes. Future RCTs that compare two interventions and include a control group will allow us to better understand treatment effects in the context of spontaneous maturation and will allow further comparison of different interventions as well as the investigation of moderating factors.

Plain-language summary: We identified two trials involving 154 minimally verbal children who had ASD (aged 32 months to 11 years). The studies randomly divided participants into those that received a communication intervention and a control group that did not receive the intervention but received treatment as usual in the community. Both studies focused primarily on communication outcomes (verbal and non-verbal). One of the studies also collected information on social communication. Neither study collected information on adverse events, other communication skills, quality of life or behavioural outcomes. One study looked at an alternative and augmentative communication (ACC) intervention (Picture Exchange Communication System; PECS), which teachers gave the children in school. This intervention was conducted over five months and involved teacher training and consultation. PECS is a staged approach where children are taught to exchange a single picture of a desired item or action to another person who then responds to the request. The system progresses toward putting pictures together in sentences and using these sentences in a variety of ways such as commenting and answering questions. This study included 84 participants (73 boys) aged 4 to 11 years and was funded by the Three Guineas Trust. The other study looked at a verbally based intervention (focused playtime intervention; FPI), which is a home-based parent education programme that aims to promote coordinated play with toys between parents and their children. This study included 70 participants (64 boys) aged 32 months to 82 months and was funded by a Clinical and Patient Educators Association grant (HD35470) from the National Institute of Child Health and Human Development, the MIND Institute Research Program, and a Professional Staff Congress-City University of New York grant. There is limited evidence that verbally based and AAC interventions improve spoken and non-verbal communication in minimally verbal children with ASD. Both studies included in this review reported gains in aspects of verbal or non-verbal communication (or both) for some children immediately after the intervention. Neither of the interventions resulted in improvements in verbal or non-verbal communication that were maintained over time for most children. We rated the overall quality of the evidence as very low because we only found two eligible studies, and they involved few participants. Furthermore, both studies had some methodological limitations that increased their risk of bias. There is currently limited evidence that verbally based and ACC interventions improve expressive communication skills in minimally verbal children with ASD aged 32 months to 11 years. Additional trials that use communication interventions and compare the effects of these interventions to a control group are urgently required to build the evidence base.