The Pediatric Autism Research Cohort (PARC) Study: protocol for a patient-oriented prospective study examining trajectories of functioning in children with autism.

INTRODUCTION: The developmentally variable nature of autism poses challenges in providing timely services tailored to a child's needs. Despite a recent focus on longitudinal research, priority-setting initiatives with stakeholders highlighted the importance of studying a child's day-to-day functioning and social determinants of health to inform clinical care. To address this, we are conducting a pragmatic multi-site, patient-oriented longitudinal investigation: the Pediatric Autism Research Cohort (PARC) Study. In young children (<7 years of age) newly diagnosed with autism, we will: (1) examine variability in trajectories of adaptive functioning from the point of diagnosis into transition to school; and (2) identify factors associated with trajectories of adaptive functioning. METHODS AND ANALYSIS: We aim to recruit 1300 children under 7 years of age with a recent (within 12 months) diagnosis of autism from seven sites: six in Canada; one in Israel. Participants will be followed prospectively from diagnosis to age 8 years, with assessments at 6-month intervals. Parents/caregivers will complete questionnaires administered via a customized online research portal. Following each assessment timepoint, families will receive a research summary report describing their child's progress on adaptive functioning and related domains. Analysis of the longitudinal data will map trajectories and examine child, family and service characteristics associated with chronogeneity (interindividual and intraindividual heterogeneity over time) and possible trajectory turning points around sensitive periods like the transition to school. ETHICS AND DISSEMINATION: Ethics approvals have been received by all sites. All parents/respondents will provide informed consent when enrolling in the study. Using an integrated knowledge translation approach, where stakeholders are directly engaged in the research process, the PARC Study will identify factors associated with trajectories of functioning in children with autism. Resulting evidence will be shared with government policy makers to inform provincial and national programs. Findings will be disseminated at conferences and published in peer-reviewed journals.

Construct Validity of the Autism Classification System of Functioning: Social Communication (ACSF:SC) Across Childhood and Adolescence.

This study examined the construct validity of the Autism Classification System of Functioning: Social Communication (ACSF). Participants included 145 parents of children with autism (2-19 years). The degree of convergent and discriminant validity between parent reported ACSF and subscales from Social Responsiveness Scale 2nd edition and Behavior Assessment System for Children, 3rd Edition were examined against a priori hypotheses. We examined construct validity in the entire sample as well as in specific age cohorts. Our findings suggest that ACSF can provide a valid classification system of social communication ability in children with autism 2-19 years of age, and its two subscales may be used to examine different aspects of social communication ability.

Continuity of trajectories of autism symptom severity from infancy to childhood.

BACKGROUND: Behavioral symptom trajectories are informative of the development of young children at increased likelihood for autism spectrum disorder (ASD). METHODS: Developmental trajectories of early signs were examined in a cohort of siblings of children diagnosed with ASD (n = 502) from 6 to 18 months using the Autism Observation Scale for Infants (AOSI), and from 18 months to 5-7 years using the Autism Diagnostic Observation Schedule (ADOS). Diagnostic outcomes for ASD at age 3 confirmed diagnosis for 137 children. We further analyzed the conditional probability of a switch from a trajectory measured with the AOSI to a trajectory measured with the ADOS as well as predictors from age 6 months. RESULTS: We derived three early trajectories of behavioral signs ("Low," "Intermediate," and "Increasing") from 6 to 18 months using the AOSI. We then derived three similar, distinct trajectories for the evolution of symptom severity between 18 and 60-84 months of age (Low, Intermediate, Increasing) using the ADOS. Globally, the Low trajectory included children showing fewer ASD signs or symptoms and the Increasing trajectory included children showing more severe symptoms. We also found that most children in the Low AOSI trajectory stayed in the corresponding ADOS trajectory, whereas children in an Increasing AOSI trajectory tended to transition to an Intermediate or Increasing ADOS trajectory. Developmental measures taken at 6 months (early signs of ASD, Fine Motor, and Visual Reception skills) were predictive of trajectory membership. CONCLUSIONS: Results confirm substantial heterogeneity in the early emergence of ASD signs in children at increased likelihood for ASD. Moreover, we showed that the way those early behavioral signs emerge in infants is predictive of later symptomatology. Results yield clear clinical implications, supporting the need to repeatedly assess infants at increased likelihood for ASD as this can be highly indicative of their later development and behavior.

Community implementation of a brief parent mediated intervention for toddlers with probable or confirmed autism spectrum disorder: feasibility, acceptability, and drivers of success (IE Drmic et al.).

Background: Social ABCs is a caregiver-mediated Naturalistic Developmental Behavioral Intervention for toddlers with confirmed/suspected Autism Spectrum Disorder (ASD), with evidence in controlled research settings. Information is lacking on implementation in community settings. We reported on the treatment effectiveness of this program within a community setting, and the current paper describes the implementation phase of this work. Distinguishing between treatment and implementation effectiveness is critical for transporting interventions from laboratory to community. Objectives: Describe the implementation of Social ABCs through a large public autism service, supported by a research-community partnership. Methods: We describe this project through the Exploration, Preparation, Implementation, Sustainment (EPIS) framework as it focuses on implementation of evidence-based practices in publicly funded services. We apply this framework to the reporting stage. This project took place in the context of a 3-year government-funded pilot at a hospital-based publicly funded autism service. Participants: Program developers; Autism Service team; toddlers with suspected/confirmed ASD aged 14-34 months (M = 25.18 months) and their caregivers. Training/supervision: Provided by program developers at tapering intensity. Evaluation: Caregivers completed the Caregiver Diary and satisfaction surveys. We explored training processes, intervention uptake, acceptability, adaptations to fit community context, appropriateness, perceived impact, and facilitators/barriers. Results: Six coaches were trained to fidelity, and three of these were further trained as Site Trainers. 183 clinically referred families enrolled and 89.4% completed the 12-week program. Caregivers reported increases in adherence and competence, high satisfaction and perceived benefits for their children. Coaches reported high satisfaction. Toddlers were appropriately identified to receive the intervention. Referral processes improved, including decreased referral age, and increased family readiness for diagnostic assessment and subsequent services. Conclusions: Social ABCs was successfully implemented in a community service through a research-community partnership. The program was feasible, acceptable, and appropriate within a community context. Drivers of success included funding, institutional support, shared decision-making, adaptations to fit context, leadership support, perceived positive impact, and commitment to evaluation.

The Family-Check-Up® Autism Implementation Research (FAIR) Study: protocol for a study evaluating the effectiveness and implementation of a family-centered intervention within a Canadian autism service setting.

Introduction: Prevalence rates of emotional and behavior problems (EBP) in autistic children and youth are high (40-70%), and often cause severe and chronic impairment. Furthermore, autistic children are also more likely to experience family "social-ecological" adversity compared to neurotypically developing peers, including social isolation, child maltreatment, caregiver mental illness, and socioeconomic risk. These family stressors increase the risk of co-occurring EBP among autistic children and can often impede access to evidence-based care, thus amplifying long-term health inequities for autistic children and their caregivers. In the current autism services landscape, there are few scalable, evidence-based programs that adequately address these needs. The Family Check-Up (FCU®) is a brief, strength-based, and tailored family-centered intervention that supports positive parenting and explicitly assesses the social determinants of child and family mental health within an ecological framework. Studies have demonstrated long-term positive child and caregiver outcomes in other populations, but the FCU® has not been evaluated in families of autistic children and youth. Therefore, we aimed to evaluate FCU® implementation within an established, publicly funded Autism Program in Ontario, Canada, with delivery by autism therapists, to demonstrate sustainable effectiveness within real-world settings. Methods: In this study, we outline the protocol for a hybrid implementation-effectiveness approach with two key components: (1) A parallel-arm randomized controlled trial of N = 80 autistic children/youth (ages 6-17 years) and high levels of EBP and their caregivers. Primary and secondary outcomes include child EBP, and caregiver well-being and parenting. (2) A mixed methods implementation study, to describe facilitators and barriers to implementation of the FCU® within an autism service setting. Discussion: Scalable, ecologically focused family-centered interventions offer promise as key components of a public health framework aimed at reducing mental health inequities among autistic children, youth, and their caregivers. Results of this study will inform further program refinement and scale-up.

Adaptation, Content Validity and Reliability of the Autism Classification System of Functioning for Social Communication: From Toddlerhood to Adolescent-Aged Children with Autism.

The Autism Classification System of Functioning: Social Communication (ACSF) describes social communication functioning levels. First developed for preschoolers with ASD, this study tests an expanded age range (2-to-18 years). The ACFS rates the child's typical and best (i.e., capacity) performance. Qualitative methods tested parent and clinician perspectives of the ACSF age expansion using content analysis. The ACSF was used twice by parents and professionals for the same child/youth. Reliabilities were assessed using weighted kappa. Content validity supported the ACSF's applicability, clarity, and usability. The ACSF adaptations did not change its original construct. Reliability were calculated from 90 parent and professional Time-1 and Time-2 ratings for children/youth (2.1-15.6 years). Results showed good-to-very good intra-rater agreement (typical) and good inter-rater agreement (capacity).

Temperament in Infancy Predicts Internalizing and Externalizing Problem Behavior at Age 5 in Children With an Increased Likelihood of Autism Spectrum Disorder.

Differences in temperament have been linked to later mental health. Children with autism spectrum disorder (ASD) have an increased likelihood of experiencing such problems, including anxiety, depression, attention deficit/hyperactivity disorder, and oppositional defiant disorder; yet, relations between early temperament and later mental health are not well understood. In this paper, we assess the relationship between temperament in infancy and internalizing and externalizing behavior at age 5, in 178 children at an increased likelihood of being diagnosed with ASD (i.e., younger siblings of children with ASD). Temperament was assessed using the parent-reported Infant Behavior Questionnaire (IBQ) at 6 and 12 months of age and the Toddler Behavior Assessment Questionnaire-Revised (TBAQ-R) at 24 months of age. Mental health problems were assessed using the parent-reported Child Behavior Checklist (CBCL) at age 5. The data were analyzed using hierarchical multiple regressions, with individual temperament subscale scores as single predictor variables (Subscale Score) or temperament profiles using confirmatory factor analyses (Person-Centered Profile) in the first block, Autism Diagnostic Observation Schedule total severity scores at age 3 in the second block, and expressive and receptive language scores (from Mullen Scales of Early Learning) at age 3 in the third block for each model. Three main findings were: (1) 4 of 6 IBQ subscales at both 6 and 12 months significantly predicted internalizing and externalizing problems at age 5; (2) 9 and 8 of 13 TBAQ-R subscales at 24 months significantly predicted internalizing and externalizing problems, respectively, at age 5; and (3) a "sticky attention" temperament profile significantly predicted internalizing problems, whereas a "low-focused" profile significantly predicted externalizing problems, both at age 5. The results of this study support the supposition that temperament is a trans-diagnostic risk factor for later mental health conditions. Exploring temperament profiles and trajectories may illuminate early avenues for prevention in siblings of children with ASD who are at an increased likelihood of experiencing mental health problems, regardless of ASD diagnostic status.

Precursors of self-regulation in infants at elevated likelihood for autism spectrum disorder.

Research concerning temperament in children and adults with autism spectrum disorder (ASD) has suggested a consistent profile of low positive affect, high negative affect, and low regulation (Visser et al., 2016). One area receiving less attention is individual differences among children diagnosed with ASD. The primary objective of this study was to use a person-centered approach to explore heterogeneity of early temperament precursors of regulation in a large sample of infants with elevated familial likelihood of ASD. Early precursors of regulation included temperament assessed at 6, 12, and 24 months whereas outcome measures were diagnosis of ASD, cognitive ability and adaptive behavior at 36 months. Participants included 176 low-likelihood and 473 elevated-likelihood infants, 129 of whom were diagnosed with ASD at 3 years. Results supported a three-profile solution: a well-regulated profile (high positive affect and high attentional focus and shifting), a low attention focus profile (higher attentional shifting compared to attentional focus), and a low attention shifting profile (higher attentional focus compared to attentional shifting). A higher proportion of children diagnosed with ASD were classified into the low attention shifting profile. Furthermore, children with the well-regulated profile were differentiated from the other profiles by a pattern of higher social competence and lower dysregulation whereas children with the low attention focus profile were distinguished from the other profiles by higher cognitive ability at 3 years. The findings indicate that the combination of early positive affect with attention measures may provide an enhanced tool for prediction of self-regulation and later outcomes.

Effectiveness of a parent-mediated intervention for toddlers with autism spectrum disorder: Evidence from a large community implementation.

LAY ABSTRACT: In an effort to increase access to intervention as early as possible for toddlers with autism spectrum disorder or signs thereof, many researchers have developed interventions that can be delivered by parents in their own homes. These parent-mediated approaches have gained a lot of research attention in recent years and have been found to be helpful in terms of parent and toddler learning. Several studies have used a rigorous research design (a randomized controlled trial) to show that parent-mediated intervention can work under ideal well-controlled conditions. To build on this evidence, we also need to examine whether parent-mediated interventions can be taught well through community service providers and delivered in more "real-world" conditions. This study used a research-community partnership to provide a parent-mediated intervention (called the Social ABCs) to 179 families (mean toddler age was 25 months; ranging from 14 to 34 months). Almost 90% of the families completed the 12-week program and 70% returned for a follow-up assessment 3 months later. Analyses showed that parents learned the strategies that were designed to help them support their toddlers' development. Also, toddlers made gains in their language, communication, and social skills. Importantly, parents' use of the strategies was related to toddlers' skill gains, suggesting that the use of the strategies made a difference for the toddlers. Findings support the use of parent-mediated intervention in this very young age group and suggest that such intervention approaches should be made available for community delivery.

Early trajectories of motor skills in infant siblings of children with autism spectrum disorder.

Delays in motor development are not considered a core feature of autism spectrum disorder (ASD). Yet, recent studies of infant siblings of children with ASD suggest that early delays in motor skills may be associated with later delays in developmental areas considered to be core features of an ASD diagnosis. While these studies demonstrate the longitudinal association between core features and motor delays observed at single time points, there is considerable interest in studying the trajectories of motor development over the first 3 years of life. To accomplish this, we investigated early trajectories of motor development in a cohort of 499 infant siblings of children with ASD and 176 children with no family history of ASD. Data for the current study were drawn from the prospective, multi-site, Canadian Infant Sibling Study. We evaluated trajectories of fine and gross motor development over the first 3 years using group-based trajectory modeling. Our results show that membership for both fine and gross motor trajectory groups was related to expressive language skills, receptive language skills, ASD symptom severity scores, and diagnostic classification at age 3. These results provide evidence that the trajectory of a child's early motor development may have important prognostic implications in ASD.

Symptom trajectories in the first 18 months and autism risk in a prospective high-risk cohort.

BACKGROUND: Although early autism spectrum disorder (ASD) detection strategies tend to focus on differences at a point in time, behavioral symptom trajectories may also be informative. METHODS: Developmental trajectories of early signs of ASD were examined in younger siblings of children diagnosed with ASD (n = 499) and infants with no family history of ASD (n = 177). Participants were assessed using the Autism Observation Scale for Infants (AOSI) from 6 to 18 months. Diagnostic outcomes were determined at age 3 years blind to previous assessments. RESULTS: Semiparametric group-based modeling using AOSI scores identified three distinct trajectories: Group 1 ('Low', n = 435, 64.3%) was characterized by a low level and stable evolution of ASD signs, group 2 ('Intermediate', n = 180, 26.6%) had intermediate and stable levels, and group 3 ('Inclining', n = 61, 9.3%) had higher and progressively elevated levels of ASD signs. Among younger siblings, ASD rates at age 3 varied by trajectory of early signs and were highest in the Inclining group, membership in which was highly specific (94.5%) but poorly sensitive (28.5%) to ASD. Children with ASD assigned to the inclining trajectory had more severe symptoms at age 3, but developmental and adaptive functioning did not differ by trajectory membership. CONCLUSIONS: These prospective data emphasize variable early-onset patterns and the importance of a multipronged approach to early surveillance and screening for ASD.

Investigating the Associations Between Child Autistic Symptoms, Socioeconomic Context, and Family Life: A Pilot Study.

Objective: The day-to-day experience of families with an Autistic child may be shaped by both, child characteristics and available resources, which often are influenced by the socioeconomic context of the family. Using a socioecological approach, this study explored the quantitative associations between child autistic symptoms, family socioeconomic status, and family life. Methods: Data came from the Pediatric Autism Research Cohort-PARC Study (pilot). Parents of children with a recent diagnosis of autism completed a set of assessments, including the Autism Family Experience Questionnaire, Autism Impact Measure, and a Sociodemographic Questionnaire. A series of multiple, iterative linear regression models were constructed to ascertain quantitative associations between child autistic symptoms, socioeconomic context, and family life. Results: A total of 50 children (mean age: 76 months; SD: 9.5 months; and 84% male) with data on the variables of interest were included in the analysis. The frequency of child autistic symptoms was associated with family life outcomes (p = 0.02 and R 2 = 24%). Once autistic symptom frequency, symptom impact, and sociodemographic variables were considered, parents of higher educational attainment reported worse family life outcomes compared to their lesser-educated counterparts. This cumulative regression model had considerable explanatory capability (p = 0.01, R 2 = 40%). Conclusion: This study demonstrates the utility of using a socioecological approach to examine the dynamic interplay between child characteristics and family circumstances. Our findings suggest that family life for parents (of an autistic child) who have obtained higher education is reported (by the parents themselves) as less satisfactory compared to that of parents without higher education, once adjusted for the autistic symptom frequency of child, symptom impact, and income. These findings can inform the design and delivery of more family-centered care pathways during the years following a diagnosis of autism.

Assessment of Autism Symptoms From 6 to 18 Months of Age Using the Autism Observation Scale for Infants in a Prospective High-Risk Cohort.

The objectives were to characterize behavioral signs of autism spectrum disorder (ASD) in younger siblings of diagnosed children (high-risk; HR) and examine classification features of the Autism Observation Scale for Infants (AOSI). Participants (501 HR and 180 low-risk [LR]) were assessed between 6 and 18 months using the AOSI and at age 3 for ASD diagnoses. Total AOSI scores differentiated HR infants later diagnosed with ASD starting at 12 months. ROC analyses identified 12- and 18-month cutoff scores associated with 0.52 sensitivity and 0.74 specificity and 0.73 sensitivity and 0.65 specificity, respectively. Although classification accuracy does not support use as a standalone screen, the AOSI identifies features associated with ASD starting at 6 months and differentiates HR infants with ASD by 12 months.

Screening for Behavioral Signs of Autism Spectrum Disorder in 9-Month-Old Infant Siblings.

Despite considerable progress in characterizing the early signs of autism spectrum disorder (ASD), more remains to be learned about how symptoms emerge in the first year of life. Parents with a new baby who already had at least one biological child diagnosed with ASD (high-risk) or no family history of ASD (low-risk) completed two measures when their baby was 9 months of age, the Autism Parent Screen for Infants (APSI) questionnaire and the interview-based Parent Concerns Form. Children underwent a blinded independent diagnostic assessment for ASD at age 3 years. Total scores on the APSI and the Parent Concerns Form were both able to independently differentiate high-risk children who were later diagnosed with ASD from other high-risk and low-risk children who were not. Using logistic regression, we found that the total score on the APSI predicted ASD outcomes at age 3 with 70% accuracy, but the Parent Concerns Form did not contribute any unique variance when the APSI was already in the model. The results suggest that the APSI identifies early features predictive of ASD in high-risk infants and can be used to flag them for targeted follow-up and screening.

The association between social emotional development and symptom presentation in autism spectrum disorder.

Understanding differences in social-emotional behavior can help identify atypical development. This study examined the differences in social-emotional development in children at increased risk of an autism spectrum disorder (ASD) diagnosis (infant siblings of children diagnosed with the disorder). Parents completed the Brief Infant-Toddler Social-Emotional Assessment (BITSEA) to determine its ability to flag children with later-diagnosed ASD in a high-risk (HR) sibling population. Parents of HR (n = 311) and low-risk (LR; no family history of ASD; n = 127) children completed the BITSEA when their children were 18 months old and all children underwent a diagnostic assessment for ASD at age 3 years. All six subscales of the BITSEA (Problems, Competence, ASD Problems, ASD Competence, Total ASD Score, and Red Flags) distinguished between those in the HR group who were diagnosed with ASD (n = 84) compared to non-ASD-diagnosed children (both HR-N and LR). One subscale (BITSEA Competence) differentiated between the HR children not diagnosed with ASD and the LR group. The results suggest that tracking early social-emotional development may have implications for all HR children, as they are at increased risk of ASD but also other developmental or mental health conditions.

Relationship Between Early Social-Emotional Behavior and Autism Spectrum Disorder: A High-Risk Sibling Study.

Social-emotional behavior in autism spectrum disorder (ASD) was examined among high-risk (HR; siblings of children diagnosed with ASD) and low-risk (LR; no family history of ASD) toddlers. Caregivers completed the Infant-Toddler Social Emotional Assessment (ITSEA) at 18 months, and blind diagnostic assessment for ASD was conducted at 36 months. Results indicated impairment in social-emotional functioning among HR toddlers subsequently diagnosed with ASD compared to other HR and LR toddlers, such that ITSEA domains (Internalizing, Dysregulation, Competence) and subdomains predicted later ASD symptoms and diagnosis. Receiver operating curves of optimal ITSEA cutoffs ranged from 0.23 to 0.44 for sensitivity, and 0.74 to 0.89 for specificity. Although classification accuracy for ASD was limited, group differences highlight the importance of considering social-emotional development when assessing ASD risk.

Brief Report: Evaluation of the Short Quantitative Checklist for Autism in Toddlers (Q-CHAT-10) as a Brief Screen for Autism Spectrum Disorder in a High-Risk Sibling Cohort.

This study examined the potential of the short form of the Quantitative Checklist for Autism in Toddlers (Q-CHAT-10) to identify autism spectrum disorder (ASD) in a high-risk sibling cohort. High-risk (HR; siblings of children diagnosed with ASD) and low-risk (LR; no family history of ASD) toddlers were assessed prospectively at 18 and 24 months of age using the Q-CHAT-10 and underwent blind diagnostic assessment for ASD at 36 months of age. The results indicated that at 18 and 24 months, total score differentiated between HR toddlers subsequently diagnosed with ASD from other HR and LR toddlers. The sensitivity at both time points was acceptable; however, the specificity was below the level recommended for clinical application.

Developmental trajectories of adaptive behavior in autism spectrum disorder: a high-risk sibling cohort.

BACKGROUND: Children with autism spectrum disorder (ASD) often experience impairments in adaptive behavior. METHODS: Developmental trajectories of adaptive behavior in ASD were examined in children from high-risk (siblings of children diagnosed with ASD, n = 403) and low-risk (no family history of ASD, n = 163) families. Children were assessed prospectively at 12, 18, 24, and 36 months of age using the Vineland Adaptive Behavior Scales and underwent a blind independent diagnostic assessment for ASD at 36 months of age. RESULTS: The semi-parametric group-based modeling approach using standard scores on the Adaptive Behavior Composite revealed three distinct developmental trajectories: (a) Group 1 (21.2% of sample) showed average performance at 12 months and a declining trajectory; (b) Group 2 (52.8% of the sample) showed average performance at 12 months with a slightly declining trajectory; and (c) Group 3 (26.0% of the sample) showed a higher level of adaptive behavior at 12 months and a stable trajectory. The Mullen Scales of Early Learning Early Learning Composite and the Autism Observation Scale for Infants total score at 6 and 12 months predicted trajectory membership. CONCLUSIONS: The results emphasize heterogeneous development associated with ASD and the need for interventions tailored to individual presentations.

The Autism Parent Screen for Infants: Predicting risk of autism spectrum disorder based on parent-reported behavior observed at 6-24 months of age.

This study examined whether a novel parent-report questionnaire, the Autism Parent Screen for Infants, could differentiate infants subsequently diagnosed with autism spectrum disorder from a high-risk cohort (siblings of children diagnosed with autism spectrum disorder (n = 66)) from high-risk and low-risk comparison infants (no family history of autism spectrum disorder) who did not develop autism spectrum disorder (n = 138 and 79, respectively). Participants were assessed prospectively at 6, 9, 12, 15, 18, and 24 months of age. At 36 months, a blind independent diagnostic assessment for autism spectrum disorder was completed. Parent report on the Autism Parent Screen for Infants was examined in relation to diagnostic outcome and risk status (i.e. high-risk sibling with autism spectrum disorder, high-risk sibling without autism spectrum disorder, and low-risk control). The results indicated that from 6 months of age, total score on the Autism Parent Screen for Infants differentiated between the siblings with autism spectrum disorder and the other two groups. The sensitivity, specificity, and positive and negative predictive validity of the Autism Parent Screen for Infants highlight its potential for the early screening of autism spectrum disorder in high-risk cohorts.

Parent and clinician agreement regarding early behavioral signs in 12- and 18-month-old infants at-risk of autism spectrum disorder.

Parent and clinician agreement regarding early behavioral signs of Autism Spectrum Disorder (ASD) in children from a high-risk cohort (siblings of children diagnosed with ASD, n = 188) was examined. Infants were assessed prospectively at 12 and 18 months of age using the clinician administered Autism Observational Scale for Infants (AOSI) and the Autism Parent Screen for Infants (APSI) and underwent a blind independent diagnostic assessment for ASD at 36 months of age. Direct comparison of parent and clinician ratings showed poor agreement on all early behavioral signs, with parent-reported symptoms being better able to differentiate between children with and without ASD at both 12 and 18 months of age compared to clinician observations during a brief office visit. The results suggest that parents may detect some clinically informative behaviors based on their day-to-day observations more readily than do clinicians during brief clinical assessments, a result that needs to be replicated in a non-sibling cohort. Autism Res 2018, 11: 539-547. © 2018 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: Parents of children at high-risk of autism spectrum disorder (ASD; have an older sibling with ASD) and clinicians were compared on their reporting of 19 early signs of autism. Direct comparison of parent and clinician ratings showed poor agreement on all early behavioral signs, with parent-reported symptoms being better able to differentiate between children with and without ASD at both 12 and 18 months of age compared to clinician observations during a brief office visit. This suggests that parents may have important information regarding early development of their high-risk child.