Paediatric Autism Communication Therapy (PACT) in Children With Autism Spectrum Disorder

Autism symptoms are measured by Diagnostic Observation schedule, 2nd Edition, Calibrated Severity Score (ADOS-2 CSS). Range 0-10, with 10 indicating the highest symptom severity.

Child adaptive functioning, or personal and social skills needed for everyday living will be measured by the Vineland Adaptive Behavior Scales, 3rd Edition (VABS-3), an online questionnaire filled in by parents. Each of four domains, Communication, Daily Living Skills, Socialization and Motor Skills are divided into 3 sub-domains. Each item is scored on a Likert-type format with scores 0 (never), 1(sometimes), and 2 (usually or often). Individual items scores are summed to a raw composite score and converted into a standard scale scores. Higher scores indicate higher functioning.

Brief Observation of Social Communication Change (BOSCC) is rated on a 12-minute videotaped parent-child play-session. Each of the 15 behavioural items is coded using an empirically based decision tree that captures information regarding the behaviour including frequency and quality. Each item is rated on a 6- point scale from 0 (abnormality is not present) to 5 (abnormality is present and significantly impairs functioning). For measuring change only item 1-12 (range 0-60) are used.

Parents' assessment of their child's quality of life with Pediatric Quality of Life Inventory (PEDSQL), a questionnaire including 23 items covering four dimensions of health related quality of life. Each item is rated between 0 and 100. A higher score indicates a higher level of health-related quality of life. The mean item score is used as outcome.

Parent quality of life is measured by the questionnaire World Health Organization Quality of Life assessment- BREF (WHOQOL-BREF), including 28 items of quality of life for parents in 4 dimensions: Physiological, emotional, social and context. The item scores range from 1 to 5 with higher scores denoting higher quality of life. As the number of items differs for each subscale, the mean item score is used as outcome.

Dyadic Communication Measure for Autism (DCMA) is used to rate parent synchrony and responsiveness to the child, child communicative initiations, responses and communicative functions, and amount of mutual shared attention between parent and child will be measured by the DCMA. DCMA is rated on a 12-minute videotaped parent-child play-session. Raters will be blinded to treatment allocation.

Caregivers' implementation of PACT strategies will be measured by the Measure of Naturalistic Developmental Behavioral Intervention Strategy Implementation - Caregiver Change (MONSI-CC) rated on a 12-minute videotaped parent-child play-session. Each of 21 items are rated between 1 (strategy was rarely implemented) and 5 (strategies were well-timed) and summed on different subscales. Raters will be blinded to treatment allocation.

Child symptoms and problems are measured by the Child Behavior Checklist for ages 1½-5 (CBCL/1½-5). A 99 item questionnaire generating a Total problem Score (range 0-198). Higher score indicating more problems

Participant family life functioning will be measured by the Autism Family Experience Questionnaire (AFEQ). A parent-reported questionnaire with 48 items (range 48-240). High score indication low function.

The presence and severity of social impairment will be measured by the Social Responsiveness Scale, 2nd Edition (SRS-2). A parent reported questionnaire with 65 items identifying the presence and severity of social impairment. Each item is scored on a 4 point Likert-scale: 1 ("not true"); 2 ("sometimes true); 3 (often true); and 4 ("almost always true"). Scores are obtained for five Treatment Subscales: Social Awareness; Social Cognition; Social Communication; Social Motivation; and Restricted Interests and Repetitive Behavior. Higher scores indicating more severe impairment.

Parental reflective functioning will be measured by the Parental Reflective Functioning Questionnaire (PRFQ-1) with 18 items all rated on a 7-point scale with (7 if you strongly agree; and 1 if you strongly disagree. The midpoint, if you are neutral or undecided, is 4). High score indicate highly or hyper- reflective

Parents' perception of their child's attachment is rated on the Maternal Perception of Child Attachment (MPCA). This parent-report measure consists of 23 items rated on a 5-point rating scale, ranging from frequently (1) to never (5). High scores indicate maternal perceptions of strong child attachment.

Adverse events that occur during the study will be measured by the Negative Effects Questionnaire (NEQ). The NEQ questionnaire measures six factors; symptoms, quality, dependency, stigma, hopelessness, and failure. The self-report measure consists of three parts. First, respondents endorse specific items in case they have occurred or not during treatment, yes/no (1/0). Second, the respondents rate how negatively the negative effect was on four-point Likert-scale, ranging from "Not at all" to "Extremely" (0-4). Third, the respondents attribute the negative effect to "The treatment I received" yes/no (1/0).

Serious Adverse Events (SAE) defined as any adverse event (AE) that results in death, is life-threatening, requires hospitalisation or prolongation of existing hospitalisation, or results in persistent or significant disability or incapacity is registered continuously through patient files

The costs of delivering PACT combined with MAU compared to MAU alone will be estimated through cost-effectiveness analyses of intervention deliveries and parents' productivity loss

Parents' perceptions of the intervention will be explored in a subsample of parents in each intervention group by qualitative interviews

Child receptive language as measured by the Mullens Scales of Early Learning (MSEL). The MSEL consists of four cognitive scales: Visual Reception, Fine Motor, Receptive Language, Expressive Language, as well as a Gross Motor Scale, and can be administered to infants and children up to 5 years, 6 months of age. The MSEL receptive language raw scores will be used for the total study population in order to use the same instrument for all children, even when some of them may be older than the validated target group.

Child language as measured by the New Reynell Developmental Language Scale (NRDLS). The NRDLS covers a number of important aspects of language acquisition including vocabulary, sentence structure, verb morphology, inference, and grammaticality judgement. NRDLS is developed for children 2-7 years of age. The NRDLS raw scores will be used for the total study population in order to use the same instrument for all children, even when some of them may older than the validated target group at follow-up.