Preschool Autism Communication Trial Research Articles

Economic analysis of early intervention for autistic children: findings from four case studies in England, Ireland, Italy and Spain.

Many autistic children experience difficulties in their communication and language skills development, with consequences for social development into adulthood, often resulting in challenges over the life-course and high economic impacts for individuals, families, and society. The Preschool Autism Communication Trial (PACT) intervention is effective in terms of improved social communication and some secondary outcomes. A previously published within-trial economic analysis found that results at 13months did not support its cost-effectiveness. We modeled cost-effectiveness over 6years and across four European countries. Using simulation modeling, we built on economic analyses in the original trial, exploring longer-term cost-effectiveness at 6years (in England). We adapted our model to undertake an economic analysis of PACT in Ireland, Italy, and Spain. Data on resource use were taken from the original trial and a more recent Irish observational study. PACT is cost-saving over time from a societal perspective, even though we confirmed that, at 13months post-delivery, PACT is more expensive than usual treatment (across all countries) when given to preschool autistic children. After 6years, we found that PACT has lower costs than usual treatment in terms of unpaid care provided by parents (in all countries). Also, if we consider only out-of-pocket expenses from an Irish study, PACT costs less than usual treatment. PACT may be recommended as a cost-saving early intervention for families with an autistic child.

An adapted social communication intervention at home and education to promote social communication change in children with severe autism: the PACT-G RCT

Background Prior evidence suggests that behaviours closely related to the intervention delivered for autism are amenable to change, but it becomes more difficult when generalising treatment effects beyond that immediate context. Objectives The objectives were (1) to test an early autism social communication intervention designed to promote child social communication change in the naturalistic contexts of both home and education, with an additive effect on overall child symptom outcomes, and (2) to conduct a mechanistic study investigating the transmission of treatment effects within and across contexts to an overall treatment effect. Design The trial was a three-site, parallel-group, randomised controlled trial of the experimental treatment plus treatment as usual and treatment as usual alone. The primary intention-to-treat analysis used analysis of covariance. The mechanism analysis used regression models to test mediation of the primary outcome by parent–child and education staff (learning support assistant)–child social interactions. Setting The study took place in three urban/semiurban regions in Manchester, Newcastle upon Tyne and London. Participants Children aged 2–11 years who met the criteria for severe autism. Interventions The Preschool Autism Communication Trial was adapted to parallel components within home and educational settings using in-person and remote delivery. Treatment as usual was the control condition. Main outcome measures The primary outcome was autism symptoms on the Autism Diagnostic Observation schedule-2. The secondary outcomes were Brief Observation of Social Communication Change, dyadic social interaction between child and parent or learning support assistant, reported language, functional outcome and reduction in child disruptive behaviour. Outcomes were measured at baseline and at the 12-month end point in all settings; interim mechanism measurements were taken at 7 months. Results Participants (n = 249; 122 in the PACT-G group and 127 in the treatment-as-usual group; 51 were female and 197 were male) received a median of 10 (interquartile range 8–12) sessions at home and 8 (interquartile range 5–10) sessions in an educational setting. We found no significant treatment effects on the end-point Autism Diagnostic Observation Schedule-2 primary outcome (–0.04, 95% confidence interval –0.26 to 0.18; p = 0.734), on the end-point Brief Observation of Social Communication Change secondary outcome (–0.03, 95% confidence interval –0.31 to 0.25; p = 0.85) or on language, repetitive behaviour, adaptive behaviour and child well-being. We did find significant treatment effects on dyadic interactions (increased parent synchronous response 0.54, 95% confidence interval 0.39 to 0.69; p = 0.001); child initiations with a parent (0.27, 95% confidence interval 0.12 to 0.41; p = 0.001); learning support assistant synchronous response (0.32, 95% confidence interval 0.14 to 0.49; p = 0.001); child initiations with a learning support assistant (0.21, 95% confidence interval 0.06 to 0.36; p = 0.005); and unblinded measures of improved parental well-being and child disruptive behaviour across home and educational settings. Adult (parent/learning support assistant) synchronous responsiveness in a home/education setting improved child dyadic social initiation. The child dyadic social initiation was also associated with child symptoms on researcher Brief Observation of Social Communication Change. Limitations The delivered sessional dosage was 83% of that planned in the home setting and 67% in the educational setting, with 5.5% of home sessions and 5% of educational sessions deemed ‘unacceptable’, particularly for remote delivery. A change of therapy learning support assistant was experienced by over one-third of children by the mid-point of the trial, by another third by the end point, and by one-fifth at both points. Conclusions The multicomponent Paediatric Autism Communication Trial – Generalised (PACT-G) treatment for a child in a home or educational setting did not produce the hypothesised improvement in child autism symptomatology or adaptive behaviour, but did produce significant improvements in proximal adult–child reciprocal dyadic communication. Future work Future work will involve building on these results towards a further understanding of delivery options, dosage and multicomponent extension of social communication interventions for young children with autism in naturalistic settings. Trial registration Current Controlled Trials ISRCTN25378536. Funding This project was funded by the Efficacy and Mechanism Evaluation programme, a Medical Research Council and National Institute for Health and Care Research (NIHR) partnership. This was also part funded by the NIHR Biomedical Research Centre at South London and Maudsley NHS Foundation Trust and King’s College London. This will be published in full in Efficacy and Mechanism Evaluation; Vol. 9, No. 3. See the NIHR Journals Library website for further project information.

Promotion of Parental Responsivity: Implications for Population-Level Implementation and Impact.

Promotion of Parental Responsivity: Implications for Population-Level Implementation and Impact.

Utility of the Autism Diagnostic Observation Schedule and the Brief Observation of Social and Communication Change for Measuring Outcomes for a Parent-Mediated Early Autism Intervention.

Measuring outcomes for autistic children following social communication interventions is an ongoing challenge given the heterogeneous changes, which can be subtle. We tested and compared the overall and item‐level intervention effects of the Brief Observation of Social Communication Change (BOSCC), Autism Diagnostic Observation Schedule (ADOS‐2) algorithm, and ADOS‐2 Calibrated Severity Scores (CSS) with autistic children aged 2–5 years from the Preschool Autism Communication Trial (PACT). The BOSCC was applied to Module 1 ADOS assessments (ADOS‐BOSCC). Among the 117 children using single or no words (Module 1), the ADOS‐BOSCC, ADOS algorithm, and ADOS CSS each detected small non‐significant intervention effects. However, on the ADOS algorithm, there was a medium significant intervention effect for children with “few to no words” at baseline, while children with “some words” showed little intervention effect. For the full PACT sample (including ADOS Module 2, total n=152), ADOS metrics evidenced significant small (CSS) and medium (algorithm) overall intervention effects. None of the Module 1 item‐level intervention effects reached significance, with largest changes observed for Gesture (ADOS‐BOSCC and ADOS), Facial Expressions (ADOS), and Intonation (ADOS). Significant ADOS Module 2 item‐level effects were observed for Mannerisms and Repetitive Interests and Stereotyped Behaviors. Despite strong psychometric properties, the ADOS‐BOSCC was not more sensitive to behavioral changes than the ADOS among Module 1 children. Our results suggest the ADOS can be a sensitive outcome measure. Item‐level intervention effect plots have the potential to indicate intervention “signatures of change,” a concept that may be useful in future trials and systematic reviews.Lay SummaryThis study compares two outcome measures in a parent‐mediated therapy. Neither was clearly better or worse than the other; however, the Autism Diagnostic Observation Schedule produced somewhat clearer evidence than the Brief Observation of Social Communication Change of improvement among children who had use of “few to no” words at the start. We explore which particular behaviors are associated with greater improvement. These findings can inform researchers when they consider how best to explore the impact of their intervention.

Predictors of reliable symptom change: Secondary analysis of the Preschool Autism Communication Trial

Background and aims Despite recent gains in the amount and quality of early autism intervention research, identifying what works for whom remains an ongoing challenge. Exploiting data from the Preschool Autism Communication Trial (PACT), we undertook secondary analysis to explore prognostic indicators and predictors of response to one year of PACT therapy versus treatment as usual within this large and rigorously characterised cohort recruited across three UK trial sites. Methods In this secondary analysis of variability in child gains on the primary trial outcome measure – social-communication symptom severity – we used a pragmatic and data-driven approach to identify a subgroup of children who showed reliable improvement and a subgroup showing clear lack thereof. We then tested which among several baseline child and family factors – including measures routinely collected in research trials and clinical practice – varied as a function of child outcome status and treatment group. Results Greater baseline child non-verbal ability was a significant prognostic indicator of symptom reduction over time (i.e. irrespective of treatment group). By contrast, parent synchrony presented as marginal predictor, and trial recruitment site as a significant predictor, of differential outcome by treatment group. Specifically, lower parent synchrony showed some association with poorer outcomes for children from families assigned to treatment as usual (but with no such effect for those assigned to PACT). Similarly, children at one recruitment site were more likely to have poorer outcomes if assigned to treatment as usual, compared to children at the same site assigned to PACT. Conclusions The current data contribute to an evidence base indicting that early non-verbal ability is a robust indicator of generally better prognosis for young children with autism. Lower parent synchrony and a broadly more deprived socio-geographical context may inform the appropriate targeting of PACT. That is, given that the former factors predicted poorer outcome in children from families assigned to treatment as usual, the receipt of a relatively low-dose, parent-mediated and communication-focused therapy might be developmentally protective for young children with autism. Nevertheless, results from this study also highlight the paucity of meaningful predictors of outcome among routine clinical characterisation measures such as those investigated here. Implications Understanding the factors associated with differential treatment outcomes is critical if we are to individualise treatment decisions for children with autism. Inherently tied to this objective is a need to delineate those factors which specifically predict positive response (or lack of response) to one or other treatment option, versus those that indicate generally better (or poorer) prognosis, irrespective of treatment.

The Autism Family Experience Questionnaire (AFEQ): An Ecologically-Valid, Parent-Nominated Measure of Family Experience, Quality of Life and Prioritised Outcomes for Early Intervention

There is a lack of measures that reflect the intervention priorities of parents of children with autism spectrum disorder (ASD) and that assess the impact of interventions on family experience and quality of life. The Autism Family Experience Questionnaire (AFEQ) was developed through focus groups and online consultation with parents, and reflected parental priorities. It was then administered to the parents of children enrolled in the Pre-school Autism Communication Trial and its 6-year follow-up study. The AFEQ showed good convergent validity with well-established measures of child adaptive functioning, parental mental health and parental wellbeing. It was sensitive to change in response to a parent-mediated intervention for young children with autism, showing treatment effect at treatment endpoint which increased at six-year follow-up.

Parent-led early intervention can reduce symptom severity.

In the original Preschool Autism Communication Trial (PACT), published in 2010, 152 children aged 2-4 with autism were randomised to receive usual treatment or a 12-month early intervention.

Parent-mediated social communication therapy for young children with autism (PACT): long-term follow-up of a randomised controlled trial

SummaryBackgroundIt is not known whether early intervention can improve long-term autism symptom outcomes. We aimed to follow-up the Preschool Autism Communication Trial (PACT), to investigate whether the PACT intervention had a long-term effect on autism symptoms and continued effects on parent and child social interaction.MethodsPACT was a randomised controlled trial of a parent-mediated social communication intervention for children aged 2–4 years with core autism. Follow-up ascertainment was done at three specialised clinical services centres in the UK (London, Manchester, and Newcastle) at a median of 5·75 years (IQR 5·42–5·92) from the original trial endpoint. The main blinded outcomes were the comparative severity score (CSS) from the Autism Diagnostic Observation Schedule (ADOS), the Dyadic Communication Assessment Measure (DCMA) of the proportion of child initiatiations when interacting with the parent, and an expressive-receptive language composite. All analyses followed the intention-to-treat principle. PACT is registered with the ISRCTN registry, number ISRCTN58133827.Findings121 (80%) of the 152 trial participants (59 [77%] of 77 assigned to PACT intervention vs 62 [83%] of 75 assigned to treatment as usual) were traced and consented to be assessed between July, 2013, and September, 2014. Mean age at follow-up was 10·5 years (SD 0·8). Group difference in favour of the PACT intervention based on ADOS CSS of log-odds effect size (ES) was 0·64 (95% CI 0·07 to 1·20) at treatment endpoint and ES 0·70 (95% CI −0·05 to 1·47) at follow-up, giving an overall reduction in symptom severity over the course of the whole trial and follow-up period (ES 0·55, 95% CI 0·14 to 0·91, p=0·004). Group difference in DCMA child initiations at follow-up showed a Cohen's d ES of 0·29 (95% CI −0.02 to 0.57) and was significant over the course of the study (ES 0·33, 95% CI 0·11 to 0·57, p=0·004). There were no group differences in the language composite at follow-up (ES 0·15, 95% CI −0·23 to 0·53).InterpretationThe results are the first to show long-term symptom reduction after a randomised controlled trial of early intervention in autism spectrum disorder. They support the clinical value of the PACT intervention and have implications for developmental theory.FundingMedical Research Council.

Effectiveness of the parent-mediated intervention for children with autism spectrum disorder in south Asia in India and Pakistan (PASS): a randomised controlled trial

Autism spectrum disorder affects more than 5 million children in south Asia. Although early interventions have been used for the treatment of children in high-income countries, no substantive trials have been done of the interventions adapted for use in low-income and middle-income countries (LMICs). We therefore assessed the feasibility and acceptability of the parent-mediated intervention for autism spectrum disorder in south Asia (PASS) in India and Pakistan. A single-blind randomised trial of the comparison of 12 sessions of PASS (plus treatment as usual) with treatment as usual alone delivered by non-specialist health workers was done at two centres in Goa, India, and Rawalpindi, Pakistan. Children aged 2-9 years with autism spectrum disorder were randomly assigned (1:1) by use of probabilistic minimisation, controlling for treatment centre (Goa or Rawalpindi), age (<6 years or ≥6 years), and functional impairment (Vineland Adaptive Behaviour Scale Composite score <65 or ≥65). The primary outcome was quality of parent-child interaction on the Dyadic Communication Measure for Autism at 8 months. Analysis was by intention to treat. The study is registered with ISRCTN, number ISRCTN79675498. From Jan 1 to July 30, 2013, 65 children were randomly allocated, 32 to the PASS group (15 in Goa and 17 in Rawalpindi) and 33 to the treatment-as-usual group (15 in Goa and 18 in Rawalpindi). 26 (81%) of 32 participants completed the intervention. After adjustment for minimisation factors and baseline outcome, the primary outcome showed a treatment effect in favour of PASS in parental synchrony (adjusted mean difference 0·25 [95% CI 0·14 to 0·36]; effect size 1·61 [95% CI 0·90 to 2·32]) and initiation of communication by the child with the parent (0·15 [0·04 to 0·26]; effect size 0·99 [0·29 to 1·68]), but time in mutual shared attention was reduced (-0·16 [-0·26 to -0·05]; effect size -0·70 [-1·16 to -0·23]). Our results show the feasibility of adapting and task-shifting an intervention used in a high-income context to LMICs. The findings also replicate the positive primary outcome treatment effects of a parent-mediated communication-focused intervention in the original UK Preschool Autism Communication Trial, with one negative effect not reported previously. Autism Speaks, USA.

Cost-effectiveness analysis of a communication-focused therapy for pre-school children with autism: results from a randomised controlled trial.

BackgroundAutism is associated with impairments that have life-time consequences for diagnosed individuals and a substantial impact on families. There is growing interest in early interventions for children with autism, yet despite the substantial economic burden, there is little evidence of the cost-effectiveness of such interventions with which to support resource allocation decisions. This study reports an economic evaluation of a parent-mediated, communication-focused therapy carried out within the Pre-School Autism Communication Trial (PACT).Methods152 pre-school children with autism were randomly assigned to treatment as usual (TAU) or PACT + TAU. Primary outcome was severity of autism symptoms at 13-month follow-up. Economic data included health, education and social services, childcare, parental productivity losses and informal care.ResultsClinically meaningful symptom improvement was evident for 53 % of PACT + TAU versus 41 % of TAU (odds ratio 1.91, p = 0.074). Service costs were significantly higher for PACT + TAU (mean difference £4,489, p < 0.001), but the difference in societal costs was smaller and non-significant (mean difference £1,385, p = 0.788) due to lower informal care rates for PACT + TAU.ConclusionsImprovements in outcome generated by PACT come at a cost. Although this cost is lower when burden on parents is included, the cost and effectiveness results presented do not support the cost-effectiveness of PACT + TAU compared to TAU alone.Trial registrationCurrent Controlled Trials ISRCTN58133827Electronic supplementary materialThe online version of this article (doi:10.1186/s12888-015-0700-x) contains supplementary material, which is available to authorized users.

Treatment mechanism in the MRC preschool autism communication trial: implications for study design and parent-focussed therapy for children.

The PACT randomised-controlled trial evaluated a parent-mediated communication-focused treatment for children with autism, intended to reduce symptom severity as measured by a modified Autism Diagnostic Observation Schedule-Generic (ADOS-G) algorithm score. The therapy targeted parental behaviour, with no direct interaction between therapist and child. While nonsignificant group differences were found on ADOS-G score, significant group differences were found for both parent and child intermediate outcomes. This study aimed to better understand the mechanism by which the PACT treatment influenced changes in child behaviour though the targeted parent behaviour. Mediation analysis was used to assess the direct and indirect effects of treatment via parent behaviour on child behaviour and via child behaviour on ADOS-G score. Alternative mediation was explored to study whether the treatment effect acted as hypothesised or via another plausible pathway. Mediation models typically assume no unobserved confounding between mediator and outcome and no measurement error in the mediator. We show how to better exploit the information often available within a trial to begin to address these issues, examining scope for instrumental variable and measurement error models. Estimates of mediation changed substantially when account was taken of the confounder effects of the baseline value of the mediator and of measurement error. Our best estimates that accounted for both suggested that the treatment effect on the ADOS-G score was very substantially mediated by parent synchrony and child initiations. The results highlighted the value of repeated measurement of mediators during trials. The theoretical model underlying the PACT treatment was supported. However, the substantial fall-off in treatment effect highlighted both the need for additional data and for additional target behaviours for therapy.

Predictors of parent–child interaction style in dyads with autism

Parent synchrony has been shown to be developmentally important for the growth of communication skills in young children with autism. Understanding individual-differences in parent synchrony and other associated features of dyadic interaction therefore presents as an important step toward the goal of appreciating how and why some parent-child dyads come to adopt more optimal interaction styles, while for others, parent interaction is more asynchronous and less developmentally facilitative. Within the large, well-characterized Preschool Autism Communication Trial (PACT) cohort, baseline parent-child interaction samples were coded for three key aspects of dyadic interaction style; - Parent Synchrony, Child Initiation, and Shared Attention. We explored associations among these measures, demographic characteristics and standardized child assessment scores. While various child factors were associated with each of the interaction measures, very few associations were observed with parent/familial factors. Child language age-equivalence was a significant positive predictor of variation in each interaction measure, while child repetitive symptoms predicted reduced Shared Attention. The three interaction measures were moderately positively inter-related. In the context of childhood autism, variation in dyadic interaction style appears to be driven more by child language and repetitive behaviors than age, social-communication symptoms and non-verbal ability. Parent/family factors contributed little to explaining variability in parent-child interaction, in the current study.

FC14-05 - Parent-mediated communication-focused treatment for preschool children with autism (MRC PACT); a randomised controlled trial

IntroductionEvidence from previous small trials has suggested the effectiveness of early social communication interventions for autism.ObjectivesThe Preschool Autism Communication Trial (PACT) investigated the efficacy of such an intervention in the largest psychosocial autism trial to date.AimsTo provide a stringent test of a pre-school communication intervention for autism.Methods152 children with core autism aged 2 years - 4 years 11 months in a 3 site 2 arm single (assessor) blinded randomised controlled trial of the parent-mediated communication-focused intervention added to treatment as usual (TAU) against TAU alone. Primary outcome; severity of autism symptoms (modified social communication algorithm from Autism Diagnostic Observation Schedule-Generic, ADOS-G). Secondary outcomes; blinded measures of parent-child interaction, child language, and adaptation in school.ResultsAt 13 month endpoint the treatment resulted in strong improvement in parental synchronous response to child (adjusted between-group effect size 1.22 (95% CI 0.85, 1.59) and child initiations with parent (ES 0.41 (0.08, 0.74) but small effect on autism symptomatology (ADOS-G, ES -0.24 (95% CI -0.59, 0.11) ns). Parents (not blind to allocation) reported strong treatment effects on child language and social adaptation but effects on blinded research assessed language and school adaptation were small.ConclusionsAddition of the PACT intervention showed clear benefit in improving parent-child dyadic social communication but no substantive benefit over TAU in modifying objectively rated autism symptoms. This attenuation on generalisation from ‘proximal’ intervention effects to wider symptom change in other contexts remains a significant challenge for autism treatment and measurement methodology.

Parent-mediated communication-focused treatment in children with autism (PACT): a randomised controlled trial

SummaryBackgroundResults of small trials suggest that early interventions for social communication are effective for the treatment of autism in children. We therefore investigated the efficacy of such an intervention in a larger trial.MethodsChildren with core autism (aged 2 years to 4 years and 11 months) were randomly assigned in a one-to-one ratio to a parent-mediated communication-focused (Preschool Autism Communication Trial [PACT]) intervention or treatment as usual at three specialist centres in the UK. Those assigned to PACT were also given treatment as usual. Randomisation was by use of minimisation of probability in the marginal distribution of treatment centre, age (≤42 months or >42 months), and autism severity (Autism Diagnostic Observation Schedule-Generic [ADOS-G] algorithm score 12–17 or 18–24). Primary outcome was severity of autism symptoms (a total score of social communication algorithm items from ADOS-G, higher score indicating greater severity) at 13 months. Complementary secondary outcomes were measures of parent-child interaction, child language, and adaptive functioning in school. Analysis was by intention to treat. This study is registered as an International Standard Randomised Controlled Trial, number ISRCTN58133827.Results152 children were recruited. 77 were assigned to PACT (London [n=26], Manchester [n=26], and Newcastle [n=25]); and 75 to treatment as usual (London [n=26], Manchester [n=26], and Newcastle [n=23]). At the 13-month endpoint, the severity of symptoms was reduced by 3·9 points (SD 4·7) on the ADOS-G algorithm in the group assigned to PACT, and 2·9 (3·9) in the group assigned to treatment as usual, representing a between-group effect size of −0·24 (95% CI −0·59 to 0·11), after adjustment for centre, sex, socioeconomic status, age, and verbal and non-verbal abilities. Treatment effect was positive for parental synchronous response to child (1·22, 0·85 to 1·59), child initiations with parent (0·41, 0·08 to 0·74), and for parent-child shared attention (0·33, −0·02 to 0·68). Effects on directly assessed language and adaptive functioning in school were small.InterpretationOn the basis of our findings, we cannot recommend the addition of the PACT intervention to treatment as usual for the reduction of autism symptoms; however, a clear benefit was noted for parent-child dyadic social communication.FundingUK Medical Research Council, and UK Department for Children, Schools and Families.

Early social communication interventions for autism

Given the impact of autism as a disorder there has been surprisingly little rigorous research into its treatment. Positive findings from pilot trials of parent-child interventions have led to funding of the Pre-school Autism Communication Trial, which will be an important step in developing an evidence base for early intervention.

Caregiver interactions with young autistic children

It is not known whether early intervention can improve long-term autism symptom outcomes. We aimed to follow-up the Preschool Autism Communication Trial (PACT), to investigate whether the PACT intervention had a long-term effect on autism symptoms and continued effects on parent and child social interaction.PACT was a randomised controlled trial of a parent-mediated social communication intervention for children aged 2–4 years with core autism. Follow-up ascertainment was done at three specialised clinical services centres in the UK (London, Manchester, and Newcastle) at a median of 5·75 years (IQR 5·42–5·92) from the original trial endpoint. The main blinded outcomes were the comparative severity score (CSS) from the Autism Diagnostic Observation Schedule (ADOS), the Dyadic Communication Assessment Measure (DCMA) of the proportion of child initiatiations when interacting with the parent, and an expressive-receptive language composite. All analyses followed the intention-to-treat principle. PACT is registered with the ISRCTN registry, number ISRCTN58133827.121 (80%) of the 152 trial participants (59 [77%] of 77 assigned to PACT intervention vs 62 [83%] of 75 assigned to treatment as usual) were traced and consented to be assessed between July, 2013, and September, 2014. Mean age at follow-up was 10·5 years (SD 0·8). Group difference in favour of the PACT intervention based on ADOS CSS of log-odds effect size (ES) was 0·64 (95% CI 0·07 to 1·20) at treatment endpoint and ES 0·70 (95% CI −0·05 to 1·47) at follow-up, giving an overall reduction in symptom severity over the course of the whole trial and follow-up period (ES 0·55, 95% CI 0·14 to 0·91, p=0·004). Group difference in DCMA child initiations at follow-up showed a Cohen's d ES of 0·29 (95% CI −0.02 to 0.57) and was significant over the course of the study (ES 0·33, 95% CI 0·11 to 0·57, p=0·004). There were no group differences in the language composite at follow-up (ES 0·15, 95% CI −0·23 to 0·53).The results are the first to show long-term symptom reduction after a randomised controlled trial of early intervention in autism spectrum disorder. They support the clinical value of the PACT intervention and have implications for developmental theory.Medical Research Council.