A Conceptual Model of Angelman Syndrome and Review of Relevant Clinical Outcomes Assessments (COAs)

Developmental milestones and daily living skills in individuals with Angelman syndrome

BACKGROUND

Angelman syndrome (AS) is a neurodevelopmental disorder associated with severe global developmental delay. However, the ages at which different developmental skills are achieved in these individuals remain unclear. We seek to determine the probability and the age of acquisition of specific developmental milestones and daily living skills in individuals with AS across the different molecular subtypes, viz. class I deletion, class II deletion, uniparental disomy, imprinting defect, and UBE3A variants.

METHODS

Caregivers participating in a longitudinal multicenter Angelman Syndrome Natural History Study completed a questionnaire regarding the age at which their children achieved specific developmental milestones and daily living skills. The Cox Proportional Hazard model was applied to analyze differences in the probability of achievement of skills at various ages among five molecular subtypes of AS.

RESULTS

Almost all individuals, regardless of molecular subtype, were able to walk with support by five years of age. By age 15, those with a deletion had at least a 50% probability of acquiring 17 out of 30 skills compared to 25 out of 30 skills among those without a deletion. Overall, fine and gross motor skills such as holding and reaching for small objects, sitting, and walking with support were achieved within a fairly narrow range of ages, while toileting, feeding, and hygiene skills tend to have greater variability in the ages at which these skills were achieved. Those without a deletion had a higher probability (25-92%) of achieving daily living skills such as independently toileting and dressing compared to those with a deletion (0-13%). Across all molecular subtypes, there was a low probability of achieving independence in bathing and brushing teeth.

CONCLUSION

Individuals with AS without a deletion are more likely to achieve developmental milestones and daily living skills at an earlier age than those with a deletion. Many individuals with AS are unable to achieve daily living skills necessary for independent self-care.

Outcome measures in Angelman syndrome

BACKGROUND

Angelman syndrome (AS) is a rare neurodevelopmental disorder characterized by severe intellectual disability, little to no expressive speech, visual and motor problems, emotional/behavioral challenges, and a tendency towards hyperphagia and weight gain. The characteristics of AS make it difficult to measure these children's functioning with standard clinical tests. Feasible outcome measures are needed to measure current functioning and change over time, in clinical practice and clinical trials.

AIM

Our first aim is to assess the feasibility of several functional tests. We target domains of neurocognitive functioning and physical growth using the following measurement methods: eye-tracking, functional Near-Infrared Spectroscopy (fNIRS), indirect calorimetry, bio-impedance analysis (BIA), and BOD POD (air-displacement plethysmography). Our second aim is to explore the results of the above measures, in order to better understand the AS phenotype.

METHODS

The study sample consisted of 28 children with AS aged 2-18 years. We defined an outcome measure as feasible when (1) at least 70% of participants successfully finished the measurement and (2) at least 60% of those participants had acceptable data quality. Adaptations to the test procedure and reasons for early termination were noted. Parents rated acceptability and importance and were invited to make recommendations to increase feasibility. The results of the measures were explored.

RESULTS

Outcome measures obtained with eye-tracking and BOD POD met the definition of feasibility, while fNIRS, indirect calorimetry, and BIA did not. The most important reasons for early termination of measurements were showing signs of protest, inability to sit still and poor/no calibration (eye-tracking specific). Post-calibration was often applied to obtain valid eye-tracking results. Parents rated the BOD POD als most acceptable and fNIRS as least acceptable for their child. All outcome measures were rated to be important. Exploratory results indicated longer reaction times to high salient visual stimuli (eye-tracking) as well as high body fat percentage (BOD POD).

CONCLUSIONS

Eye-tracking and BOD POD are feasible measurement methods for children with AS. Eye-tracking was successfully used to assess visual orienting functions in the current study and (with some practical adaptations) can potentially be used to assess other outcomes as well. BOD POD was successfully used to examine body composition.

TRIAL REGISTRATION

Registered d.d. 23-04-2020 under number 'NL8550' in the Dutch Trial Register: https://onderzoekmetmensen.nl/en/trial/23075.

Child characteristics associated with child quality of life and parenting stress in Angelman syndrome

BACKGROUND

Angelman syndrome (AS) is a rare neurodevelopmental disorder characterised by severe intellectual disability, movement disorder, epilepsy, sleeping problems, and behavioural issues. Little is known on child health-related quality of life (HRQoL) in AS. AS family studies have reported elevated parenting stress and a high impact of the child's syndrome on the parent. It is unclear which factors influence child HRQoL and parenting stress/impact in AS.

METHODS

We collected data prospectively through standardised clinical assessments of children with AS at the ENCORE Expertise centre for Angelman Syndrome at the Erasmus MC Sophia Children's Hospital. A linear regression analysis was conducted for the following outcome variables: (1) child HRQoL (Infant and Toddler Quality of Life Questionnaire); (2) the impact of the child's syndrome on the parent (Infant and Toddler Quality of Life Questionnaire); and (3) parenting stress (Parenting Stress Index). Predictor variables were child genotype, epilepsy, sleeping problems (Sleep Disturbance Scale for Children), cognitive developmental level (Bayley Cognition Scale), autistic features (Autism Diagnostic Observation Schedule) and emotional/behavioural problems (Child Behaviour Checklist). Covariates were sex, age and socio-economic status.

RESULTS

The study sample consisted of 73 children with AS, mean age = 9.1 years, range = 2-18 years. Emotional/behavioural problems were the strongest significant predictor of lowered child HRQoL. Internalising problems were driving this effect. In addition, having the deletion genotype and higher age was related to lower child HRQoL. Sleeping problems were related to a higher impact of the child's syndrome on the parent. Finally, emotional/behavioural problems were associated with higher parenting stress. Cognitive developmental level, autistic features and epilepsy were not a significant predictor of child HRQoL and parenting stress/impact.

CONCLUSIONS

These results suggest that interventions aimed at increasing child HRQoL and decreasing parenting stress/impact in AS should focus on child emotional/behavioural problems and sleeping problems, using a family-centred approach.

Quality of Life in Angelman Syndrome: A Caregivers' Survey

BACKGROUND

Angelman syndrome (AS) is a genetic disorder, characterized by a cheerful disposition with bouts of laughter, developmental delay, speech impairment, ataxia, and seizures. Previous AS surveys have focused on the natural history, describing seizure types and response to anti-seizure medications.

METHODS

A web-based survey was distributed to caregivers of individuals with AS to characterize motor function, cannabidiol (CBD) use, and factors affecting quality of life (QOL).

RESULTS

Of a total of 183 individuals with AS (mean age 19.4 ± 13.4 years; 48.1% female), 72% had sleep problems, 80% had seizures, and 32% had one or more emergency department visits in the previous year. Eighty-eight percent were ambulatory (with or without assistance), and half experienced falls, 10.4% resulting in serious injury. Caregivers reported physical therapy, antiseizure medication, CBD, and clonidine as helpful. Inability to walk, falls/drops, sleep problems, and seizures significantly affected QOL (P < 0.002, <0.001, <0.001, P = 0.001, respectively). QOL was not influenced by gender, distance to the hospital, or genetic abnormality.

CONCLUSIONS

These findings suggest that seizures are the tip of the iceberg. Use of a brief, valid screening tool can assist providers with identifying and addressing issues of primary concern to caregivers of individuals with AS.

Qualitative Insights into Key Angelman Syndrome Motor Related Concepts Reported by Caregivers-A Thematic Analysis of Semi-Structured Interviews

Previous patient-centered concept models of Angelman syndrome (AS) are integral in developing our understanding of the symptoms and impact of this condition with a holistic perspective and have highlighted the importance of motor function. We aimed to develop the motor and movement aspects of the concept models, to support research regarding motor-related digital outcomes aligned with patients' and caregivers' perspectives. We conducted a qualitative analysis of semi-structured interviews of 24 caregivers to explore AS motor-related features, factors influencing them and their impact on patients and caregivers.The most impacted motor features were gait, walking and stair-climbing. Half of caregivers ranked motor symptoms as one of the most burdensome symptoms of AS. Caregivers frequently reported physical therapy, motivation, medical management and age as factors influencing motor function in AS and reported that impaired motor function affected both patients and caregivers. Measures of lower-limb motor function were identified as relevant to monitor drug effectiveness in AS. Caregivers discussed expected benefits of a digital outcome and potential issues with wearable technology in the context of AS. We propose a new motor function patient-centered concept model, providing insights for the development of relevant, motor-related, digital outcomes in AS.

Enabling endpoint development for interventional clinical trials in individuals with Angelman syndrome: a prospective, longitudinal, observational clinical study (FREESIAS)

BACKGROUND

Angelman syndrome (AS) is a rare neurodevelopmental disorder characterized by the absence of a functional UBE3A gene, which causes developmental, behavioral, and medical challenges. While currently untreatable, comprehensive data could help identify appropriate endpoints assessing meaningful improvements in clinical trials. Herein are reported the results from the FREESIAS study assessing the feasibility and utility of in-clinic and at-home measures of key AS symptoms.

METHODS

Fifty-five individuals with AS (aged < 5 years: n = 16, 5-12 years: n = 27, ≥ 18 years: n = 12; deletion genotype: n = 40, nondeletion genotype: n = 15) and 20 typically developing children (aged 1-12 years) were enrolled across six USA sites. Several clinical outcome assessments and digital health technologies were tested, together with overnight 19-lead electroencephalography (EEG) and additional polysomnography (PSG) sensors. Participants were assessed at baseline (Clinic Visit 1), 12 months later (Clinic Visit 2), and during intermittent home visits.

RESULTS

The participants achieved high completion rates for the clinical outcome assessments (adherence: 89-100% [Clinic Visit 1]; 76-91% [Clinic Visit 2]) and varied feasibility of and adherence to digital health technologies. The coronavirus disease 2019 (COVID-19) pandemic impacted participants' uptake of and/or adherence to some measures. It also potentially impacted the at-home PSG/EEG recordings, which were otherwise feasible. Participants achieved Bayley-III results comparable to the available natural history data, showing similar scores between individuals aged ≥ 18 and 5-12 years. Also, participants without a deletion generally scored higher on most clinical outcome assessments than participants with a deletion. Furthermore, the observed AS EEG phenotype of excess delta-band power was consistent with prior reports.

CONCLUSIONS

Although feasible clinical outcome assessments and digital health technologies are reported herein, further improved assessments of meaningful AS change are needed. Despite the COVID-19 pandemic, remote assessments facilitated high adherence levels and the results suggested that at-home PSG/EEG might be a feasible alternative to the in-clinic EEG assessments. Taken altogether, the combination of in-clinic/at-home clinical outcome assessments, digital health technologies, and PSG/EEG may improve protocol adherence, reduce patient burden, and optimize study outcomes in AS and other rare disease populations.

Developing Angelman syndrome-specific clinician-reported and caregiver-reported measures to support holistic, patient-centered drug development

BACKGROUND

Angelman syndrome (AS) is a rare, heterogenous neurogenetic condition, which significantly impacts the lives of people with AS and their families. Valid and reliable measures reporting key symptoms and functional impairments of AS are required to support development of patient-centered therapies. We describe the development of clinician- and caregiver-reported, AS-specific Global Impression scales for incorporation into clinical trials. Best practice US Food and Drug Administration guidance for measure development was followed with input from expert clinicians, patient advocates, and caregivers during content generation and refinement.

RESULTS

Initial measurement domains for the Symptoms of AS-Clinician Global Impression (SAS-CGI) and the Caregiver-reported AS Scale (CASS) were identified from a conceptual disease model of AS symptoms and impacts, derived from interviews with caregivers and clinicians. Two rounds of cognitive debriefing (CD) interviews were performed; clinicians debriefed the SAS-CGI, with patient advocates and caregivers debriefing the CASS to ensure relevance and comprehension. Feedback was used to refine items and ensure wording was age-appropriate and captured AS-specific symptoms, as well as associated impacts and functional impairments. The SAS-CGI and CASS capture global assessments of seizures, sleep, maladaptive behaviors, expressive communication, fine and gross motor skills, cognition, and self-care, which were determined by clinicians, patient advocates, and caregivers to be the most challenging aspects of AS. Additionally, the measures include items for assessing overall AS symptoms and the meaningfulness of any change. In addition to ratings for severity, impact, and change, a notes field was included in the SAS-CGI to provide the rationale for the chosen rating. CD interviews confirmed the measures covered key concepts of AS from the perspective of clinicians and caregivers, and demonstrated that the measures' instructions, items, and response options were clear and appropriate. Interview feedback informed adjustments to the wording of the instructions and the items.

CONCLUSIONS

The SAS-CGI and CASS were designed to capture multiple AS symptoms, reflecting the heterogeneity and complexity of AS in children 1 to 12 years old. These clinical outcome assessments have been incorporated into AS clinical studies, which will allow for the evaluation of their psychometric properties and inform further refinements if needed.

A disease concept model for STXBP1-related disorders

OBJECTIVE

STXBP1-related disorders are rare genetic epilepsies and neurodevelopmental disorders, but the impact of symptoms across clinical domains is poorly understood. Disease concept models are formal frameworks to assess the lived experience of individuals and their families and provide a basis for generating outcome measures.

METHODS

We conducted semistructured, qualitative interviews with 19 caregivers of 16 individuals with STXBP1-related disorders and 7 healthcare professionals. We systematically coded themes using NVivo software and grouped concepts into the domains of symptoms, symptom impact, and caregiver impact. We quantified the frequency of concepts throughout the lifespan and across clinical subgroups stratified by seizure history and developmental trajectories.

RESULTS

Over 25 hours of interviews, we coded a total of 3626 references to 38 distinct concepts. In addition to well-recognized clinical features such as developmental delay (n = 240 references), behavior (n = 201), and seizures (n = 147), we identified previously underrepresented symptoms including gastrointestinal (n = 68) and respiratory symptoms (n = 24) and pain (n = 30). The most frequently referenced symptom impacts were autonomy (n = 96), socialization (n = 64), and schooling (n = 61). Emotional impact (n = 354), support (n = 200), and daily life & activities (n = 108) were highly cited caregiver impacts. We found that seizures were more commonly referenced in infancy than in other age groups, while behavior and socialization were more likely to be referred to in childhood. We found that caregivers of individuals with ongoing seizures were less likely to reference developmental delay, possibly due to the relatively high impact of seizures.

SIGNIFICANCE

STXBP1-related disorders are complex conditions affecting a wide range of clinical and social domains. We comprehensively mapped symptoms and their impact on families to generate a comprehensive disease model as a foundation for clinical endpoints in future trials.

Health-related quality of life and medication use among individuals with Angelman syndrome

PURPOSE

The primary goal of this analysis is to describe the health-related quality of life (HRQoL), medical history, and medication use among adolescents and adults individuals with Angelman syndrome (AS).

METHODS

The analysis uses baseline data collected during the STARS study, a double-blind placebo controlled trial of gaboxadol (OV101) in adolescents and adults with AS. The HRQoL was estimated using EuroQoL 5-Dimension 5-Level (EQ-5D) health questionnaire proxy 1 version, which was completed by the caregivers. EQ-5D consists of two parts, a 5-dimension descriptive and a visual analogue scale (VAS) component. The utility score derived from EQ-5D ranges from 0 to 1 (perfect health) and VAS ranges from 0 to 100 (perfect health).

RESULTS

87 individuals with AS were included in the present analysis. The mean utility score was 0.44 ± 0.20 and VAS score was 84 ± 1.5. The EQ-5D data indicated that the self-care, mobility and daily activities were most impacted. All adolescents (100%) and most adults (93%) had at least moderate problems with self-care activities, such as washing or dressing themselves. More than half (55%) of the adolescents and adults had at least moderate issues with mobility and usual activities. Approximately, 30% of adolescents and adults had moderate to extreme problems with anxiety/depression. High baseline concomitant use of medications was observed across both age groups with an average of 5 medications being used per person.

CONCLUSION

This study highlights the impact of AS on HRQoL and medication utilization among adolescents and adults individuals with AS.

Sleep problems in children with Angelman Syndrome: The effect of a behavioral intervention program

BACKGROUND & AIMS

The aim of this study was to investigate the effect of a behavioral intervention on sleep problems, which are significant and an unmet clinical need in children with Angelman Syndrome (AS).

METHODS & PROCEDURES

Children (2-18 years) with AS and sleep problems were randomized to a behavioral intervention program or a control group. Intervention consisted of a standardized program including home visits, psycho-education, feedback based on direct observation of bedtime routine and video footage of the night and behavioral treatment techniques by a behavioral therapist. Change in sleep duration (primary) and parental sleep, nighttime visits, sleep hygiene, daytime behavior, parental stress and quality of life (secondary) were assessed post-intervention and at follow-up using questionnaires, diary, actigraphy and videosomnography.

OUTCOMES & RESULTS

The groups, 9 children in each, did not differ at baseline. We found a significant effect of intervention on wake after sleep onset with classical statistical analysis (videosomnography). With single case analysis we found a positive effect on total sleep time (diary and actigraphy) and wake after sleep onset (diary) with a persistent effect on total sleep time (actigraphy) and wake after sleep onset (diary). On secondary outcome there was a significant and persistent effect on sleep hygiene and several quality of life domains.

CONCLUSIONS & IMPLICATIONS

Behavioral intervention has a positive and persistent effect on sleep problems in children with AS. We advise psycho-education for all parents and use of videosomnography for both evaluation of and feedback on sleep behavior patterns, individual behavioral advice and specific behavioral techniques for children with sleep problems.

A draft conceptual model of SLC6A1 neurodevelopmental disorder

Introduction

SLC6A1 Neurodevelopmental Disorder (SLC6A1-NDD), first described in 2015, is a rare syndrome caused by a mutation in the SLC6A1 gene which encodes for the GABA Transporter 1 (GAT-1) protein. Epilepsy is one of the most common symptoms in patients and is often the primary treatment target, though the severity of epilepsy is variable. The impact of seizures and other symptoms of SLC6A1-NDD on patients and caregivers is wide-ranging and has not been described in a formal disease concept study.

Methods

A literature search was performed using the simple search term, "SLC6A1." Papers published before 2015, and those which did not describe the human neurodevelopmental disorder were removed from analysis. Open-ended interviews on lived experiences were conducted with two patient advocate key opinion leaders. An analysis of de-identified conversations between families of people with SLC6A1-NDD on social media was performed to quantify topics of concern.

Results

Published literature described symptoms in all of the following domains: neurological, visual, motor, cognitive, communication, behavior, gastrointestinal, sleep, musculo-skeletal, and emotional in addition to epilepsy. Key opinion leaders noted two unpublished features: altered hand use in infants, and developmental regression with onset of epilepsy. Analysis of social media interactions confirmed that the core symptoms of epilepsy and autistic traits were prominent concerns, but also demonstrated that other symptoms have a large impact on family life.

Discussion

For rare diseases, analysis of published literature is important, but may not be as comprehensive as that which can be gleaned from spontaneous interactions between families and through qualitative interviews. This report reflects our current understanding of the lived experience of SLC6A1-NDD. The discrepancy between the domains of disease reported in the literature and those discussed in patient conversations suggests that a formal qualitative interview-based disease concept study of SLC6A1-NDD is warranted.

Estimating the impact of Angelman syndrome on parental productivity in Australia using productivity-adjusted life years

BACKGROUND

Angelman syndrome (AS) is a rare genetic condition characterized by global developmental delay, including severe intellectual disability. The parents of persons with AS experience increased stress, anxiety, and depression. This impacts parents' career choices and productivity.

OBJECTIVE

To estimate, for the first time, the total productivity lost by the parents of persons with AS over a 10-year period in Australia and the corresponding cost to society.

METHODS

A cost-of-illness model with simulated follow-up over a 10-year period was developed, with 2019 as the baseline year, facilitated by a Markov chain of life tables. The prevalence of persons with AS and their parents, the productivity-adjusted life years (PALYs) lost by parents, and the cost to society were estimated. Key data were obtained from a prospective cohort of AS families, peer-reviewed literature, and publicly available sources.

RESULTS

The base-case productivity burden borne by the estimated 330 living parents of the 428 prevalent persons with AS totaled AUD$45.30 million, corresponding to a loss of 38.42% of PALYs per parent.

CONCLUSIONS

Caring for a child with AS has a significant impact on the productivity of affected parents, with a large associated impact on the broader Australian economy.

Feasibility of wearable technology for 'real-world' gait analysis in children with Prader-Willi and Angelman syndromes

BACKGROUND

Prader-Willi syndrome (PWS) and Angelman syndrome (AS) are neurodevelopmental disorders in need of innovative 'real-world' outcome measures to evaluate treatment effects. Instrumented gait analysis (IGA) using wearable technology offers a potentially feasible solution to measure "real-world' neurological and motor dysfunction in these groups.

METHODS

Children (50% female; 6-16 years) diagnosed with PWS (n = 9) and AS (n = 5) completed 'real-world' IGA assessments using the Physilog®5 wearable. PWS participants completed a laboratory assessment and a 'real-world' long walk. The AS group completed 'real-world' caregiver-assisted assessments. Mean and variability results for stride time, cadence, stance percentage (%) and stride length were extracted and compared across three different data reduction protocols.

RESULTS

The wearables approach was found to be feasible, with all participants able to complete at least one assessment. This study also demonstrated significant agreement, using Lin's concordance correlation coefficient (CCC), between laboratory and 'real-world' assessments in the PWS group for mean stride length, mean stance % and stance % CV (n = 7, CCC: 0.782-0.847, P = 0.011-0.009).

CONCLUSION

'Real-world' gait analysis using the Physilog®5 wearable was feasible to efficiently assess neurological and motor dysfunction in children affected with PWS and AS.

The Road to Personalized Therapies: Lessons Learned From Angelman Syndrome

Angelman syndrome (AS) is a neurogenetic disorder characterized by delays including a severe expressive language delay, motor concerns, ataxia, epilepsy, sleep disturbances, gastrointestinal problems, and characteristic behaviors, including a happy demeanor, hyperactivity, and excitability. The syndrome is one of the first neurodevelopmental disorders with a clear trajectory towards meaningful treatment with approximately 20 companies actively developing targeted therapeutics for AS. Herein, we highlight the historical context of the road to therapeutics and some of the challenges in the field with the potential to impact the success of clinical trials for Angelman syndrome and also have relevance of other neurogenetic developmental disabilities.

Clinical Characterization of Epilepsy in Children With Angelman Syndrome

BACKGROUND

Epilepsy is highly prevalent in children with Angelman syndrome (AS), and its detailed characterization and relationship to the genotype (deletion vs nondeletion) is important both for medical practice and for clinical trial design.

METHODS AND MATERIALS

We retrospectively analyzed the main clinical features of epilepsy in 265 children with AS who were enrolled in the AS Natural History Study, a multicenter, observational study conducted at six centers in the United States. Participants were prospectively followed up and classified by genotype.

RESULTS

Epilepsy was reported in a greater proportion of individuals with a deletion than a nondeletion genotype (171 of 187 [91%] vs. 48 of 78 [61%], P < 0.001). Compared with participants with a nondeletion genotype, those with deletions were younger at the time of the first seizure (age: median [95% confidence interval]: 24 [21-24] months vs. 57 [36-85] months, P < 0.001) and had a higher prevalence of generalized motor seizures. Hospitalization following a seizure was reported in more children with a deletion than a nondeletion genotype (92 of 171 [54%] vs. 17 of 48 [36%], P = 0.04). The overall prevalence of absence seizures was not significantly different between genotype groups. Forty-six percent (102/219) of the individuals reporting epilepsy were diagnosed with AS concurrently or after their first seizure.

CONCLUSIONS

Significant differences exist in the clinical expression of epilepsy in AS according to the underlying genotype, with earlier age of onset and more severe epilepsy in individuals with AS due to a chromosome 15 deletion.

Development of an adapted Clinical Global Impression scale for use in Angelman syndrome

BACKGROUND

The Clinical Global Impression-Severity (CGI-S) and CGI-Improvement (CGI-I) scales are widely accepted tools that measure overall disease severity and change, synthesizing the clinician's impression of the global state of an individual. Frequently employed in clinical trials for neuropsychiatric disorders, the CGI scales are typically used in conjunction with disease-specific rating scales. When no disease-specific rating scale is available, the CGI scales can be adapted to reflect the specific symptom domains that are relevant to the disorder. Angelman syndrome (AS) is a rare, clinically heterogeneous condition for which there is no disease-specific rating scale. This paper describes efforts to develop standardized, adapted CGI scales specific to AS for use in clinical trials.

METHODS

In order to develop adapted CGI scales specific to AS, we (1) reviewed literature and interviewed caregivers and clinicians to determine the most impactful symptoms, (2) engaged expert panels to define and operationalize the symptom domains identified, (3) developed detailed rating anchors for each domain and for global severity and improvement ratings, (4) reviewed the anchors with expert clinicians and established minimally clinically meaningful change for each symptom domain, and (5) generated mock patient vignettes to test the reliability of the resulting scales and to standardize rater training. This systematic approach to developing, validating, and training raters on a standardized, adapted CGI scale specifically for AS is described herein.

RESULTS

The resulting CGI-S/I-AS scales capture six critical domains (behavior, gross and fine motor function, expressive and receptive communication, and sleep) defined by caregivers and expert clinicians as the most challenging for patients with AS and their families.

CONCLUSIONS

Rigorous training and careful calibration for clinicians will allow the CGI-S/-I-AS scales to be reliable in the context of randomized controlled trials. The CGI-S/-I-AS scales are being utilized in a Phase 3 trial of gaboxadol for the treatment of AS.

Scoping Review of Judgment-Based Measures of Ambulation with Assistive Devices for Children and Youth

AIM

To identify available judgment-based measures of ambulation with assistive devices for the purpose of examining item content and responses to aid in the expansion of the Pediatric Evaluation of Disability Inventory Computer Adaptive Test (PEDI-CAT) Mobility Domain.

METHODS

PubMed and CINAHL databases were used to identify measures meeting the following criteria: 1) applicable for children/youth; 2) self-report, proxy-report, or interview administration; and 3) assistive device (walker, cane, crutches, gait trainer) use specified or considered with responses. Population, administration, respondent(s), items, and responses were compiled. Item content was categorized and response scales grouped by type.

RESULTS

Fifteen measures met inclusion criteria. Measures included child and proxy-report. Item categories included Surfaces, Steps/Stairs, Dual Tasks, Negotiation of Environment, Distance, and Time. Only two measures distinguished between device type within items. One measure specified gait trainers. "Difficulty" and "Assistance" were the most frequently used response scales.

CONCLUSIONS

Available measures have content examining device use; however, none of the measures are comprehensive, devices are not consistently specified, and responses are imprecise. Items with well-defined responses for measuring a child's ambulation with an assistive device are needed for clinical practice, research, and program evaluation.

Measuring What Matters to Individuals with Angelman Syndrome and Their Families: Development of a Patient-Centered Disease Concept Model

Angelman syndrome (AS) is a complex, heterogeneous, and life-long neurodevelopmental disorder. Despite the considerable impact on individuals and caregivers, no disease-modifying treatments are available. To support holistic clinical management and the development of AS-specific outcome measures for clinical studies, we conducted primary and secondary research identifying the impact of symptoms on individuals with AS and their unmet need. This qualitative research adopted a rigorous step-wise approach, aggregating information from published literature, then evaluating it via disease concept elicitation interviews with clinical experts and caregivers. We found that the AS-defining concepts most relevant for treatment included: impaired expressive communication, seizures, maladaptive behavior, cognitive impairment, motor function difficulties, sleep disturbance, and limited self-care abilities. We highlight the relevance of age in experiencing these key AS concepts, and the difference between the perceptions of clinicians and caregivers towards the syndrome. Finally, we outline the impact of AS on individuals, caregivers, and families.

Adaptive Skills in FXS: A Review of the Literature and Evaluation of the PEDI-Computer Adaptive Test (PEDI-CAT) to Measure Adaptive Skills

As adaptive skills (AS) are dynamic and may indicate the success of an intervention, they are a common domain measured in clinical trials. Typical interview tools for measuring AS are time-consuming, and questionnaire measures often lead to inconsistent information. The present study was designed to evaluate the feasibility, validity and test-retest performance of the Pediatric Evaluation of Disability Inventory Computer Adaptive Test (PEDI-CAT) in Fragile X syndrome (FXS). The PEDI-CAT is administered via tablet and uses the item response theory to efficiently determine the items administered. The PEDI-CAT was administered to 42 individuals with FXS (27 males; 15 females) aged 1.6-50.9 years (M = 14.9; SD = 11.2), followed by the Vineland-3 (VABS-3) interview for comparison. Administration was efficient (M = 21.7 min; SD = 9.5; range 8-45 min; mode = 19). Males and females did not significantly differ on the PEDI-CAT domains, except for daily activities (t(40) = -2.22, p = 0.037). Floor effects were significant for both measures, although the PEDI-CAT showed more floor effects in the mobility (35.7%) and social-cognitive (50%) domains. PEDI-CAT daily activities, mobility, social-cognitive and responsibility domains were all significantly correlated with most of the VABS-3 domains (all rho > 0.5; p < 0.01). Test-rest of the PEDI-CAT was comparable to the VABS-3. Results suggest that the PEDI-CAT is efficient, and minimal training is needed to administer it; however, it lacks specificity and shares a high rate of floor effects with the VABS-3.

An overview of health issues and development in a large clinical cohort of children with Angelman syndrome

This study presents a broad overview of health issues and psychomotor development of 100 children with Angelman syndrome (AS), seen at the ENCORE Expertise Center for AS in Rotterdam, the Netherlands. We aimed to further delineate the phenotype of AS, to evaluate the association of the phenotype with genotype and other determinants such as epilepsy and to get insight in possible targets for intervention. We confirmed the presence of a more severe phenotype in the 15q11.2‐q13 deletion subtype. Novel findings were an association of (early onset of) epilepsy with a negative effect on development, a high occurrence of nonconvulsive status epilepticus, a high rate of crouch gait in the older children with risk of deterioration of mobility, a relatively low occurrence of microcephaly, a higher mean weight for height in all genetic subtypes with a significant higher mean in the nondeletion children, and a high occurrence of hyperphagia across all genetic subtypes. Natural history data are needed to design future trials. With this large clinical cohort with structured prospective and multidisciplinary follow‐up, we provide unbiased data on AS to support further intervention studies to optimize outcome and quality of life of children with AS and their family.