International Consensus on Standard Outcome Measures for Neurodevelopmental Disorders: A Consensus Statement

Importance  The use of evidence-based standardized outcome measures is increasingly recognized as key to guiding clinical decision-making in mental health. Implementation of these measures into clinical practice has been hampered by lack of clarity on what to measure and how to do this in a reliable and standardized way.

Objective  To develop a core set of outcome measures for specific neurodevelopmental disorders (NDDs), such as attention-deficit/hyperactivity disorder (ADHD), communication disorders, specific learning disorders, and motor disorders, that may be used across a range of geographic and cultural settings.

Evidence Review  An international working group composed of clinical and research experts and service users (n = 27) was convened to develop a standard core set of accessible, valid, and reliable outcome measures for children and adolescents with NDDs. The working group participated in 9 video conference calls and 8 surveys between March 1, 2021, and June 30, 2022. A modified Delphi approach defined the scope, outcomes, included measures, case-mix variables, and measurement time points. After development, the NDD set was distributed to professionals and service users for open review, feedback, and external validation.

Findings  The final set recommends measuring 12 outcomes across 3 key domains: (1) core symptoms related to the diagnosis; (2) impact, functioning, and quality of life; and (3) common coexisting problems. The following 14 measures should be administered at least every 6 months to monitor these outcomes: ADHD Rating Scale 5, Vanderbilt ADHD Diagnostic Rating Scale, or Swanson, Nolan, and Pelham Rating Scale IV; Affective Reactivity Index; Children’s Communication Checklist 2; Colorado Learning Disabilities Questionnaire; Children’s Sleep Habits Questionnaire; Developmental-Disability Children’s Global Assessment Scale; Developmental Coordination Disorder Questionnaire; Family Strain Index; Intelligibility in Context Scale; Vineland Adaptive Behavior Scale or Repetitive Behavior Scale–Revised and Social Responsiveness Scale; Revised Child Anxiety and Depression Scales; and Yale Global Tic Severity Scale. The external review survey was completed by 32 professionals and 40 service users. The NDD set items were endorsed by more than 70% of professionals and service users in the open review survey.

Conclusions and Relevance  The NDD set covers outcomes of most concern to patients and caregivers. Use of the NDD set has the potential to improve clinical practice and research.

Neurodevelopmental disorders (NDDs) are a group of conditions characterized by early-onset symptoms that cause impairments across multiple domains of functioning.¹ This work focused on 4 of the 6 Diagnostic and Statistical Manual of Mental Disorders (Fifth Edition)¹ categories of NDDs: communication disorders (language disorder, speech sound disorder, childhood-onset fluency disorder, and social [pragmatic] communication disorder), attention-deficit/hyperactivity disorder (ADHD), specific learning disorders (SLDs), and motor disorders (developmental coordination disorder, stereotypic movement disorder, Tourette disorder, and persistent [chronic] motor or vocal tic disorder). These NDDs often co-occur (eg, 25%-48% of children with ADHD have a comorbid SLD²) and are highly comorbid with other mental health or physical disorders (eg, 92% of adolescents with ADHD have experienced at least 1 coexisting mental health disorder).³ Given these high rates of co-occurrence, it is important to work transdiagnostically in the NDD field.

Collectively, NDDs are the most prevalent mental health or behavioral disorders of childhood⁴ and have a significant economic impact.⁵ The bulk of the economic costs are not borne by the health care system but instead are associated with increased well-being costs and lost productivity.⁶ Because there are effective treatments for NDDs,^7,8 these impacts and costs likely reflect that many children are not receiving treatment and that for those who are, treatments are not optimally managed, with corresponding impacts on long-term functioning and well-being.^7,9,10

Measurement-based care (MBC) is the use of routine and systematic outcome measurements before and during treatment appointments to guide clinical decision-making at the individual patient level.¹¹ Although MBC is used routinely in the management of many physical health problems (eg, glycated hemoglobin in diabetes), its use in mental health and neurodevelopmental settings is less well established¹² but has some support in ADHD.^13,14 Although the National Institute for Health and Care Excellence guidelines for ADHD¹⁵ recommend ongoing monitoring of treatment for ADHD, there is limited guidance as to how to measure clinical response and which measures to use, and the use of MBC in neurodevelopmental settings remains limited.¹² Several factors may contribute to the low uptake of MBC within these settings. Outcome measures may be considered time-consuming to use, with clinicians feeling that they do not have adequate resources to administer, score, and interpret these in a busy clinical setting or the knowledge about how to translate the scores into clinical decisions. Furthermore, many measures are available with little advice or agreement as to which should be used and how often they should be administered.

The International Consortium for Health Outcome Measurement (ICHOM) seeks to address these issues through the creation of core sets of patient-centered outcome measures (sets) for a broad range of health conditions,¹⁶ including, more recently, a focus on mental health conditions.^17,18 The ICHOM sets prioritize patient-reported outcome measures (PROMs), which reflect those outcomes seen as most important by clinicians, research experts, and service users. Sets represent the principles of value-based health care, where value is defined as the health outcomes achieved relative to the resources invested, rather than the volume of services delivered.¹⁶ In 2021, the ICHOM established an international working group comprising service user representatives, clinicians, and researchers with expertise in NDDs, with the aim of developing an NDD set. The working group chose to focus on 4 of the 6 DSM-5 categories of NDDS, excluding autism spectrum disorder (ASD) and intellectual disability (ID) (see Results for explanation). The working group followed the ICHOM principles that focus on measures that track outcomes over time rather than diagnosis or screening. The working group recognizes that the gold standard for assessment of many NDDs involves administration of measures that objectively assess and differentiate a person’s performance against normative data. However, these measures are not usually designed to measure change, and many also do not meet the ICHOM preference for PROMs and measures with minimal administrative burden and cost.

The standard ICHOM methods for developing sets was followed as per previously published sets^17-19 and are reported in accordance with Standards for Quality Improvement Reporting Excellence (SQUIRE) reporting guidelines.²⁰ The methods included a combination of research data through systematic literature searches, expert opinion, and lived experience, with decision-making through a combination of working group discussion and modified Delphi surveys. After development, the NDD set was distributed to professionals and service users for open review, feedback, and external validation.

The ICHOM sought to recruit a clinically and geographically diverse expert group with a maximum of 30 members who could provide expertise on the 4 disorders included within the scope of the NDD set. Professional working group members were chosen to represent disciplines such as public health, pediatrics, psychology, psychiatry, and psychometrics. Patient representatives were identified through their involvement in public speaking and initiatives on a national level, and professional working group members were identified by the relevance of their online work to this project (eg, journal articles and international conferences) and through recommendations by the working group chair (D.C.). All potential members were invited by an ICHOM project manager (A.J.) to participate in this project. The working group comprised 27 experts and service users from 12 countries. A core project team (M.M., U.d.S., and A.J.) coordinated and facilitated the program of work and undertook the supporting research but did not vote on the modified Delphi surveys. The chair (D.C.) did not routinely vote but could cast the deciding vote on split decisions.

The working group participated in 9 video conference calls and 8 surveys between March 1, 2021, and June 30, 2022. During calls, the working group discussed the results of research presented by the project team. A modified Delphi process was undertaken to make decisions regarding the scope of the set, outcomes and their measurement, and selection of case-mix variables and time points for measurement. Case-mix variables are measured to build risk-adjustment models to ensure fair comparisons are made of outcomes collected across health care professionals when benchmarking. Each decision regarding scope, outcomes, and measurement went through up to 3 rounds of the modified Delphi survey (see eAppendix 1 in Supplement 1 for details).

Initially, working group members were asked to define the scope of the NDD set regarding the NDDs included, the age range covered, included treatments, and settings. The NDDs to be selected were based on expert input from the project team and chair and suggestions from the working group during the first call.

Potential clinical outcomes were identified through a systematic literature search, supplemented by a search of clinical trial registries, clinical guidelines, and input from service users. As per the standard ICHOM criteria, the outcomes needed to represent the result of care, not screening or diagnosis; be important to people with NDDs; be feasible to capture; and be modifiable (Figure 1; see eTable 1 in Supplement 1 for search details).

A second systematic search was conducted in PubMed in October 2021 for each of the included outcomes using the Terwee filter¹⁹ to identify potential outcome measures (eTable 2 in Supplement 1). This search was supplemented by recommendations for tools from working group members during the surveys. The project team identified and compiled information regarding the psychometric properties (reliability, validity, and sensitivity to change), feasibility and acceptability (administrative burden, cost, and translation into >1 language), and relevance of the identified measures and shortlisted the tools that best met the criteria. The shortlisted tools were discussed by the working group and the final measures chosen through consensus on the modified Delphi surveys (eTable 3 in Supplement 1 contains information on the psychometric properties of tools).

The project team compiled a list of possible case-mix variables based on relevant articles identified in the search for outcome measures and existing ICHOM sets, including evidence describing the impact of each case-mix variable on the outcomes. The project team also prepared an initial proposal for measurement time points based on existing ICHOM sets and expert knowledge. The final case-mix variables and time points were selected through consensus on the modified Delphi surveys.

After development, the NDD set was distributed to professionals and service users who were not part of the working group for feedback and external validation. These surveys were determined to be quality improvement and thus exempt from requiring ethical board approval according to the Health Research Authority (UK), The North Star Review Board (US), and the Institute for Evidence Based Healthcare (Portugal). Professionals were invited to provide feedback on the recommended outcomes, outcome measures, reporting sources, and time points for data collection. People 18 years or older with lived experience of an NDD and parents or caregivers of children or adolescents with NDDs were invited to provide feedback on the outcomes in the NDD set (see eAppendixes 1 and 2 in Supplement 1 for details). Consent was implied through completion of the survey.

The NDDs were defined according to the DSM-5 categories: communication disorders, ADHD, specific learning disorder, and motor disorders. Although the working group agreed that an ideal NDD set of outcome measures should include ASD, a separate ICHOM set had already been developed specific to ASD,¹⁹ and it was agreed not to duplicate that work. The working group also voted to exclude ID based on the understanding that the goal of the project was to develop a standard minimum set of PROMs reflecting treatment outcomes, and intellectual abilities are not usually a focus of treatment interventions and are not well measured through PROMs. Furthermore, working group members with expertise in ID argued that ID should have its own set created by a working group with different expertise. All treatment approaches and modalities were considered in scope when reviewing the literature. The working group decided that the age range for the NDD set should be 3 to 20 years. Expert advice from working group members indicated that although many outcome measures would not be validated for the entire age range, most could be used with caution in preschool children and in those aged 18 to 20 years. However, because many of the relevant outcomes change on transition from adolescence to adulthood, the working group limited the scope to clients younger than 20 years. A strong recommendation was made that the ICHOM develop a separate set for adults with NDDs. Children younger than 3 years were excluded because diagnosis of NDDs is less reliable and less stable in this age group.

Twelve clinical outcomes were ultimately included in the NDD set spread across 3 outcome domains: (1) core symptoms related to the diagnosis; (2) impact, functioning, and quality of life (QOL); and (3) common coexisting problems (Table 1). As outlined in Table 2, 14 tools were selected to measure these outcomes. The estimated completion time of the full NDD set is 1.5 to 2 hours; thus, it may be prudent to have the initial PROMs completed before clinic attendance.

The set recommends measuring ADHD symptoms using the 18-item versions of 1 of the following measures: Swanson, Nolan, and Pelham Rating Scale IV,²¹ ADHD Rating Scale 5,²² or items 1 to 18 of the Vanderbilt ADHD Diagnostic Rating Scale.²³ These measures are comparable because items map directly onto the DSM-5 diagnostic criteria and have similar response formats. The working group did not think there was evidence to recommend one tool above the others because they are essentially equivalent.

The core symptoms of communication disorders comprise language difficulties, social (pragmatic) communication difficulties, speech sound difficulties, and fluency difficulties. The Children’s Communication Checklist 2²⁴ is recommended to assess language and social (pragmatic) communication difficulties and the Intelligibility in Context Scale²⁵ to measure speech sounds difficulties. No appropriate PROMs were identified to measure fluency difficulties; therefore, although fluency difficulties were not included as part of the minimum set of PROMs, the working group recommended that, where possible, fluency difficulties could be assessed using the clinician-reported Speech-Naturalness Scale.²⁶

Core symptom outcomes for motor disorders included fine and gross motor skills and coordination, for which the Developmental Coordination Disorder Questionnaire²⁷ is recommended. Motor disorders also included tic disorders and severity. Because an appropriate PROM was not identified to assess vocal and motor tic frequency, the working group recommended the clinician-reported Yale Global Tic Severity Scale.²⁸

The SLD outcomes included reading accuracy and comprehension, global math ability, and global writing ability. The working group recommends assessing these outcomes using the Colorado Learning Disabilities Questionnaire.²⁹

There are considerable conceptual overlaps among the domains of impact, functioning, and QOL, and these domains are often measured using similar tools. Thus, the working group chose to collapse these into a single broad category for the purpose of the NDD set.

For assessment of caregiver burden, the Family Strain Index³⁰ is recommended. The KIDSCREEN-10³¹ was chosen to track the QOL outcomes and activities of daily living. The clinician-reported Developmental-Disability Children’s Global Assessment Scale³² is recommended as a complement to the KIDSCREEN for assessing activities of daily living.

Although educational outcomes were recognized as important, these are not easy to assess via PROMs, and there is considerable variation in educational systems worldwide. We were unable to identify an appropriate PROM for educational outcomes within the health literature, and so no recommendation is made at this time.

Three of the 6 included outcomes under the domain of common coexisting problems are the focus of existing ICHOM sets. Thus, for anxiety and depression symptoms, the Revised Child Anxiety and Depression Scales (part of the ICHOM Depression & Anxiety in Children and Young People set¹⁸) is recommended. For symptoms of ASD, the Repetitive Behavior Scale–Revised and Social Responsiveness Scale or Vineland Adaptive Behavior Scale (as part of the ICHOM ASD set¹⁹) are recommended. The Affective Reactivity Index³³ and Swanson, Nolan, and Pelham Rating Scale IV²¹ are recommended to measure emotional lability/reactivity and aggression/irritability, and the Children’s Sleep Habits Questionnaire³⁴ is recommended to measure sleep problems.

An important aim of an ICHOM set is to facilitate the benchmarking of outcomes and comparisons across settings. This goal requires the collection of additional case-mix variables that can be used for risk-adjustment across varying populations and settings. The working group agreed that services should record the demographic information, baseline health status, clinical and historical factors, and treatment-related factors outlined in Table 3. Many of the case-mix variables can be measured using the Current View tool.³⁵

Because the time points for clinical contact are likely to vary considerably across services and clinicians, the NDD set recommends the minimum time points for measuring outcomes and case-mix variables outlined in Figure 2. However, the working group encourages the measurement of outcomes as frequently as is needed to optimally inform clinical decision-making. For example, it may be prudent to measure outcomes when children face changes in familial or social circumstances. It is recommended that outcomes are measured at least every 6 months or, for those taking medication, before initiation or change of medication and end of titration.

Forty service users from the UK and Portugal responded to the open review survey (20% patients and 80% parents or caregivers). The service users had lived experiences of all included NDDs, but most (73%) had experience with ADHD. Overall endorsement of the outcomes in the set exceeded the target of 70% (72%-100% across outcomes), with the exception that only 67% of service users agreed that the core symptoms of SLDs covered all important outcomes. Thirty-two professionals from 16 countries responded to the open review survey. Once again, experience in all included NDDs was represented, but ADHD was the most common (93% ADHD, 34% communication disorders, 31% SLDs, and 16% motor disorders). Endorsement of the NDD set and its components again exceeded 70% overall (70%-100% across outcomes, case-mix variables, and time points), with the exception that only 60% agreed with the proposed minimum set of outcomes for motor disorders. Review of the written feedback for outcomes that did not meet the 70% threshold indicated that the reasons behind the disagreement had already been discussed in detail by the working group during the NDD set development stage, that the feedback had already been addressed elsewhere in the NDD set, or that the comments were outside the scope of the NDD set.

It is increasingly recognized that implementing MBC for mental health conditions and NDDs can improve clinical outcomes. The working group defined a minimum NDD set of outcome measures that are low cost and available in a range of languages and appropriate and feasible to use across a range of cultural and geographic settings. The included outcomes are those that matter most to service users with a DSM-5-defined NDD, and the recommendation of a set of standard measures has the potential to improve the quality of care not only through MBC but also by increased harmonization, communication, and benchmarking across services.

The NDD set prioritizes the use of measures that are patient reported, free to use, publicly available, applicable to low- and middle-income countries, and feasible in nonspecialist as well as specialist settings as well as measures that minimize administration burden. This means that in many cases the measures recommended in the NDD set differ from the gold standards for specialist assessment. For example, an assessment of coordination and fine and gross motor skills would ideally involve a skilled clinician observing a patient performing activities related to these outcomes (eg, walking or throwing a ball). However, the included PROMs can capture a patient’s perceptions of their functioning across domains, which more closely map onto the ICHOM goal of ensuring interventions are addressing what most matters to patients.

An additional challenge when selecting outcome measures for child populations is the need to consider the views of different informants across different settings (ie, school vs home). The working group prioritized self-report and caregiver-reported measures because it is often less practical or feasible for clinicians to obtain teacher-reported measures. However, it is recommended that, when possible, information should be gathered from multiple informants across multiple settings to fully understand a child’s functioning and what adjustments (if any) should be made to treatments to maximize positive outcomes across all areas of functioning.

This study has several strengths. The working group included 2 patient representatives as voting members. The inclusion of these patient representatives in all stages of the NDD set development ensured that they were fully engaged in the decision-making process. To further support this, the working group chair actively solicited input from all members during discussions and sought the views of the patient representatives if they had not yet contributed to a discussion to help ensure diversity of input. Additional feedback from service users and professionals working in the field was also sought toward the end of the NDD set development through the open review surveys. Although the patient surveys were available in only 3 countries and completion numbers for both surveys were relatively low, the responses largely endorsed the NDD set, and feedback reflected points that had already been discussed by the working group. For the open review there was a predominance of experience with ADHD in both the service user and professional respondents. Although this may have impacted the responses, we think this is unlikely because the endorsement of outcomes did not appear to vary by experience.

This study also has some limitations. The scope of the NDD set is limited to young people aged 3 to 20 years with 1 of the specified NDDs. Some NDDs, in some cases, may be diagnosable and treatable before 3 years, and early interventions are ideal. In addition, NDDs are lifelong conditions that often continue to need treatment in adulthood. The NDD set covers several disorders that, although highly comorbid, have distinct symptoms and are quite heterogeneous. Thus, the breadth of the NDD set may come at the expense of depth for a specific disorder. The NDD set is a minimum recommendation of outcomes to measure, and the working group recommends that, where feasible, clinicians complement the NDD set with other outcome measures of importance to each individual patient.

It was difficult to identify appropriate tools to measure the outcomes across several domains. In several cases, no appropriate PROM was identified, so the working group either made no recommendation at this time or was required to recommend a clinician-reported outcome measure. Many of the identified tools were designed to be used as screening measures rather than outcome measures (eg, Developmental Coordination Disorder Questionnaire). Furthermore, many of the tools did not have evidence of sensitivity to change. Most tools do not span the entire age range (eg, validated for 6-18 years rather than 3-20 years) and are typically only validated for use in WEIRD (Western, educated, industrialized, rich, and democratic) settings and have few translations available. This was particularly an issue for those measuring SLDs and communication disorders due to the language and cultural specifications across countries and languages. Although the tools are mostly well validated in research, their use in guiding clinical decision-making is less clear and requires further research. There is a need to improve outcome measurement in NDDs, which should include codeveloping PROMs with parents and children to ensure the measures are capturing all outcomes of importance and demonstrating sensitivity to change in measures.

We have described in this consensus statement the development of a standard set of outcome measures for youth with NDDs. The NDD set covers outcomes of most concerns to patients and caregivers, including core symptoms, impact, functioning, QOL, and common coexisting conditions. Use of the NDD set has the potential to improve clinical practice and research. In the future, in addition to monitoring implementation, the working group will take responsibility for updating the NDD set when advances in measurement are made. The widespread implementation of the NDD set will create large databases that will provide a valuable resource for researchers to generate hypotheses for future research.

Accepted for Publication: April 15, 2024.

Published: June 13, 2024. doi:10.1001/jamanetworkopen.2024.16760

Open Access: This is an open access article distributed under the terms of the CC-BY License. © 2024 Mulraney M et al. JAMA Network Open.

Corresponding Author: Melissa Mulraney, PhD, Department of Paediatrics, University of Melbourne, 50 Flemington Rd, Parkville, VIC 3052, Australia (melissa.mulraney@unimelb.edu.au).

Author Contributions: Drs Mulraney and de Silva had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

Concept and design: Mulraney, de Silva, Joseph, da Luz Fialho, Banaschewski, Bandeira de Lima, Bellgrove, Chamberlain, Chan, Chong, Faraone, Guastella, Järvdike, Nagy, Newcorn, Polanczyk, Simonoff, Szatmari, Tehan, Walsh, Coghill.

Acquisition, analysis, or interpretation of data: Mulraney, de Silva, Joseph, da Luz Fialho, Dutia, Munro, Payne, Banaschewski, Bandeira de Lima, Bellgrove, Chamberlain, Chong, Clink, Cortese, Daly, Faraone, Gladstone, Guastella, Kaleem, Lovell, Meller, Nagy, Newcorn, Polanczyk, Walsh, Wamithi, Coghill.

Drafting of the manuscript: Mulraney, de Silva, Joseph, Dutia, Munro, Bellgrove, Chamberlain, Chong, Faraone, Guastella, Järvdike, Kaleem, Nagy, Wamithi, Coghill.

Critical review of the manuscript for important intellectual content: de Silva, da Luz Fialho, Munro, Payne, Banaschewski, Bandeira de Lima, Bellgrove, Chamberlain, Chan, Chong, Clink, Cortese, Daly, Faraone, Gladstone, Guastella, Järvdike, Lovell, Meller, Nagy, Newcorn, Polanczyk, Simonoff, Szatmari, Tehan, Walsh, Coghill.

Statistical analysis: de Silva, Joseph, Bellgrove, Chan.

Obtained funding: da Luz Fialho.

Administrative, technical, or material support: Mulraney, de Silva, Joseph, Dutia, Payne, Bellgrove, Chong, Cortese, Daly, Guastella, Kaleem, Meller, Simonoff, Szatmari, Tehan, Walsh, Coghill.

Supervision: de Silva, Joseph, da Luz Fialho, Bandeira de Lima, Guastella, Simonoff, Szatmari, Coghill.

Conflict of Interest Disclosures: Dr Mulraney reported receiving personal fees from the International Consortium for Health Outcomes Measurement during the conduct of the study. Dr Banaschewski reported receiving personal fees from Eye Level, Infectopharm, Medice, Neurim Pharmaceuticals, Oberberg GmbH, Takeda, and Janssen Cilag outside the submitted work and royalties from Hogrefe, Kohlhammer, CIP Medien, and Oxford University Press. Dr Bellgrove reported receiving grants from the National Health and Medical Research Council of Australia during the conduct of the study. Dr Chamberlain reported receiving honoraria for editorial work at Neuroscience and Biobehavioral Reviews and Comprehensive Psychiatry (Elsevier). Dr Cortese reported receiving personal fees from the Association for Child and Adolescent Mental Health, Canadian ADHD Resource Alliance, Medice, and British Association for Psychopharmacology and grants from the National Institute for Health and Care Research and European Research Agency outside the submitted work. Dr Faraone reported receiving grants from the National Institutes of Health, Corium Pharmaceuticals, Tris Pharmaceuticals, Supernus Pharmaceuticals, European Commission, Noven, and Shire Takeda, personal fees from Aardvark, Aardwolf, Genomind, Ironshore, Johnson & Johnson/Kenvue, Kanjo, KemPharm/Corium, Noven, Sky Therapeutics, Tris Pharmaceuticals, Otsuka, Supernus, and Butler Snow LLP; royalties from Elsevier, Guilford Press, and Oxford University Press; and stock options from Aardvark, Aardwolf, Akili, Ironshore, Sky Therapeutics, and Genomind outside the submitted work. Dr Lovell reported involvement with and support from the Association for Child and Adolescent Mental Health, (charity trustee, deputy chair, director of continuing professional development and training, communications lead for Child and Adolescent Intellectual Disability Psychiatry Network, and vice chair of the neurodevelopmental conditions special interest group; editing and speaker honoraria; and payment for time release to main employer) and the Royal College of Psychiatrists (co-opted to Child and Adolescent and Intellectual Disability faculties executive committees, member of neurodevelopmental psychiatry special interest group committee, fetal alcohol spectrum disorder group member, autism group member, and informatics group committee member); grants from the National Institute for Health and Care Research; involvement in the National Health Service (NHS) England’s Child and Adolescent Mental Health and Learning Disability/Autism programs; being a content author and editor on the MindEd and Disability Matters websites (Health Education England); serving as Professional Advisory Group vice chair with Great North Care Record; serving as a Chief Clinical Information Officer group member with Yorkshire Humber Care Record; serving as Chief Clinical Information Officer and in Local Health Care Records exemplar meetings with NHSX/NHSDDigital; receiving personal fees from Community Child Health/Kings College London, Team for the Assessment of Autism and Social Communication, Genesis Research, ADHD360, Emirates Health Services (United Arab Emirates), BJPsych, Cambridge University Press, and Maharat Arabia Learning Centre (Riyadh, Kingdom of Saudi Arabia); being a North East and North Cumbria Integrated Care Board speaker; being a Global Clinical Practice Network ICD-11, World Health Organization member; being a peer reviewer for Advances in Autism, Clinical Child Psychology and Psychiatry, British Journal Of Psychiatry, Advances in Mental Health and Intellectual Disabilities, and Developmental Medicine and Child Neurology; and authoring textbook chapters for Oxford University Press and Pavilion Publishing outside the submitted work. Dr Nagy reported receiving nonfinancial support from Egis Pharmaceuticals and personal fees from Medice outside the submitted work. Dr Newcorn reported receiving personal fees from Adlon, Cingulate Therapeutics, Corium, Hippo T&C, Ironshore, Lumos, Medice, MindTension, Myriad, Otsuka, Rhodes, Shire/Takeda, Signant Health, Supernus, the National Football League, and Klingenstein Third Generation Foundation outside the submitted work. Dr Polanczyk reported receiving personal fees from Apsen, Aché, Abbott, Medice, and Takeda outside the submitted work. Dr Coghill reported receiving grants from Takeda/Shire; personal fees from Takeda/Shire, Medice, Novartis, and Servier; and royalties from Oxford University Press and Cambridge University Press outside the submitted work. No other disclosures were reported.

Funding/Support: This project received funding from the National Health Service (NHS) England and NHS Improvement.

Role of the Funder/Sponsor: The funder had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

Data Sharing Statement: See Supplement 2.

Additional Contributions: Dido Green, PhD, PGCTHE, MSc, DipCOT, Jönköping University, Jönköping, Sweden, and Courtenay Norbury, DPhil, MSc, University College London, London, UK, provided feedback on whether the included components of the set were suitable and sufficiently captured patient or proxy perspectives of the relevant outcomes. Profs Green and Norbury did not receive any compensation for their work. We thank the lived experience users, experts, and organizations who supported this work by sharing or completing the open review surveys.