Cerebral palsy pain instruments: Recommended tools for clinical research studies by the National Institute of Neurological Disorders and Stroke Cerebral Palsy Common Data Elements project

This study describes the process of updating the cerebral palsy (CP) common data elements (CDEs), specifically identifying tools that capture the impact of chronic pain on children's functioning.

Since the initial posting of version 1.0 in December 2016, 1 the NINDS CP CDE Oversight Committee has continued to review and update the CP CDEs.
A CDE is a precisely defined question paired with a set of structured responses, used systematically across different sites, studies, or clinical trials to ensure consistent data collection. 2,3The CDE project is not a database: it is a collection of metadata and data standards.CDEs are dynamic and evolve over time.The CDEs consist of specific terminology with identification of common definitions, standardized case-report forms, and standardized tools/instruments.So far, the NINDS CDE website has contained metadata and data standards for 25 conditions (https://www.commondata eleme nts.ninds.nih.gov).The overarching aim of developing condition-specific CDEs is to accelerate research, enable prompt uptake of evidence into clinical practice, and to deliver the best quality of care to individuals who require it.Beyond research applications, the open-access comprehensive set of CP CDEs serves as a clinical tool for teaching, standardizing clinical care, harmonizing data collection and data reporting, and guiding quality-improvement projects, among others. 4Globally, the scientific community can access and use these generic or condition-specific CDEs.
Across the NINDS CDE disease groups, review and evaluation of the existing CDEs, case-report forms, and instruments occur regularly, with updates reflecting evolving knowledge in the disease groups, research gaps, and gaps within the CDEs themselves.][9][10] Cognitive and communication challenges, as well as multiple pain etiologies, complicate assessment, intervention, and management. 8,11hildren with chronic pain experience more anxiety and depression than those without it and they experience more negative physical symptoms as adults. 12,13Moreover, chronic pain has detrimental effects on the individual's personal and social life, also affecting the family environment. 14,15However, for children and young people with CP, the complex interplay of disability and pain with personal, social, and family life is not clear.As such, a biopsychosocial approach for chronic pain assessment and treatment outcomes is advisable in children and young people with CP. 13,15,16 Thus, because of the complexity of the biopsychosocial factors on chronic pain in children with CP, a stepwise approach to identifying tools that capture these factors requires a critical evaluation of potential tools and identification of gaps in measures of them.
Over the past decade, special attention has been paid to chronic pain evaluation and assessment tools for children, young people, and adults with CP, 13,[17][18][19] recognizing the major role that chronic pain plays in the health and wellbeing of people with CP.8][19][20][21] Hence, comprehensive pain assessment and evaluation remain a key area to address in CP to identify interventions to reduce chronic pain.
To fill the gap of identifying comprehensive and validated tools of chronic pain in children and young people with CP in the CP CDEs version 1.0, the NINDS CP CDE Oversight Committee Pain Working Group gathered information about existing pain tools and developed the first recommended CP CDE chronic pain tools/instruments for children and young people with CP.The specific objectives were to (1) recommend a set of tools representing the impact of chronic pain on function in children and young people with CP-guided by the International Classification of Functioning, Disability and Health (ICF); 22 (2) identify valid and reliable chronic pain tools for routine use across clinical studies and clinical practice in children and young people with CP; and (3) identify gaps in tools that could be addressed in future research.

History of NINDS CP CDEs
The NINDS CDE project for CP began in 2015.An organizing committee with representatives from the American Academy for Cerebral Palsy and Developmental Medicine and the NINDS convened at an international meeting.The Academy's leadership created a Steering Committee and worked with the Academy's Research Committee to invite experts in CP into working groups, each of which was composed of five to seven members with knowledge and experience relevant to CP-related health domains.These experts included international epidemiologists, clinicians, clinical researchers, educators, and clinical trial experts.In December 2016, the project was completed with an academic publication and the online posting of the CP CDEs.For further details see Schiariti et al. 1

What this paper adds
• The proposed chronic pain tools harmonize the assessment of chronic pain in children and young people with cerebral palsy (CP).• The new CP pain common data elements address the functional impact of chronic pain in everyday activities in children and young people with CP.

NINDS CDE terminology
Across all NINDS CDE disease groups, CDEs and tools/ instruments are classified with regard to level of recommendation for use in research studies.Consistent with this guidance across the NINDS CDE project, the CP CDE Pain Working Group sought to classify any recommended CDE or tool for pain as 'Core', 'Supplemental -Recommended', 'Supplemental', or 'Exploratory' (Table 1). 1,23

Conceptual framework
Managing the depth and breadth of data related to chronic pain and CP required an organizational framework to help visualize the essential data categories.Given the multidimensional impact of living with and experiencing CP on developmental trajectories of children and young people and their families, the ICF was used to map out the content of the tools within the framework that met inclusion criteria for this study.

Study design
The study used a multi-step methodology to address the specific objectives.First, all pain CDEs and tools listed in the NINDS CDEs repository data were reviewed.Simultaneously, a scoping review was performed in four electronic search engines to identify pain assessment tools used in studies with children with CP.Key search terms included 'chronic pain', 'cerebral palsy', and 'clinical assessment tool', with inclusion of studies published between January 2000 and January 2020.(An example search strategy is provided in Appendix S1).Second, chronic pain tools meeting the inclusion criteria were then reviewed for psychometric properties, content analysis, and reference to other pain tools or manuscripts that may have not been identified in the original search.The category(ies) of each pain tool assessed was determined with the representative domain(s) of the ICF.The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Extension for Scoping Reviews, provided in Appendix S2, guided our methodology.Lastly, the group reviewed all tools and reached a consensus on a set of validated tools that comprehensively represented the impact of chronic pain on functioning in children and young people with CP (Figure S1).The initial step to compile a list of chronic pain tools took place in 2020 (scoping review).The literature search was complemented from additional sources, including the NINDS CDEs across disorders related to pain, and the pain measures from the National Institutes of Health HEAL Initiative. 24Review of assessment tools occurred over an 18month period and included individual review of the tools, discussion of each tool, and group consensus about inclusion and exclusion criteria.Then, the group sorted candidate tools into pain domain(s), ICF components, and recommendations for CDEs.In May 2022, a set of chronic pain tools were posted for public review on the NINDS CP CDEs webpage (Appendix S3 shows the timeline of the project).

Chronic pain definition
The CP CDE Pain Working Group adopted the definition of chronic pain as pain lasting more than 3 months, clinically identified as (1) chronic musculoskeletal pain, such as persistent or recurrent pain that arises as part of CP causing structural changes to bone(s), joint(s), muscle(s), or related soft tissue(s); (2) chronic visceral pain that frequently originates from the internal organs of the abdominal (often caused by gastro-esophageal reflux) and pelvic cavities; and (3) postsurgical and posttraumatic pain that persists beyond normal healing, frequently after surgery and some types of injury. 25

Target population
The target population of this initiative was children and young people aged 0 to 18 years with a diagnosis of CP or considered to be at risk of developing CP.

Inclusion and exclusion criteria
Pain tools were reviewed and included if (1) the assessment was developed specifically for chronic pain; (2) the assessment was developed for or used in pediatric populations (children 0-18 years); (3) the main focus of the assessment was pain, or most questions included were about pain (i.e. more than three questions); (4) the assessment fitted within one of the main pain categories (Patient Reported Outcomes Measurement Information System [PROMIS] categories, or pain location); and (5) the assessment was available in English.
Pain tools were excluded if (1) the assessment was developed specifically for a different diagnosis; (2) pain was due to an event outside the scope of the diagnosis (i.e.trauma); ( 3) Core: a data element for recording essential information applicable to any CP study, including therapeutic areas and study designs; consistent with all NINDS disease-specific CDE sets.Supplemental -Highly Recommended: a data element recommended for use whenever applicable.Supplemental: a data element that has some evidence of validity and is commonly collected in clinical studies in CP; use depends upon study design.Exploratory: a data element that is emerging or that requires further validation in CP.
Abbreviations: CDE, common data element; CP, cerebral palsy; NINDS, National Institute of Neurological Disorders and Stroke.
the main focus of the assessment was not on pain or had very limited questions about pain (i.e. one to three questions); (4) the assessment did not fit within one of the pain categories (i.e.PROMIS categories and location); (5) the assessment lacked validity for use with children or young people with CP; and (6) the assessment was a duplicate.Figure S1 summarizes the multi-step study methodology.
Psychometric properties and clinical utility rating system 7][28] Specifically, the following characteristics were considered: the main purpose of the tool was to assess chronic pain, had good/acceptable validity, had good to excellent/high reliability, and had good/ acceptable clinical utility (see criteria in Appendix S4).Of note, psychometric studies on children and young people with CP were given priority, but this alone was not a reason for exclusion.Clinical utility was defined as good/acceptable if the tool was easy to score and interpret, it was not too time consuming, provided useful information about how pain affects functioning, assessed chronic pain/pain behavior, and could be used with individuals with CP, at any level of functioning (i.e.any Gross Motor Function Classification System [GMFCS] level).

Categories of chronic pain
To categorize the tools, we also used the National Institutes of Health PROMIS pain-related domains. 29These domains include items for pain intensity, interference, behavior, and quality.In addition, we considered pain location as an important domain.Descriptions of PROMIS pain-related domains are given in Appendix S5.

Public review
In May 2022, the recommended set of CP pain CDE Notice of Copyright forms were posted on the NINDS CP CDE website for public review.Notices of Copyright included detailed descriptions of every proposed tool, with psychometric characteristics.We received feedback for some of these Notices.Of note, no new pain measures were put forward for consideration during the public review.

R E SU LTS
Overall, 184 assessments were reviewed (Figure S1).After removing duplicates, 87 assessments remained for consideration.Applying exclusion criteria resulted in 15 recommended assessments.
Table 2 provides an overview of the 15 pain instruments that were recommended for chronic pain assessment in children with CP.Using the NINDS CDE language for recommended applications, 8 out of the 15 identified CP chronic pain CDEs were classified as 'Supplemental' and the remaining seven pain tools were categorized as 'Exploratory' because limited study had been published in the target group.None of the pain tools were classified as 'Core' or 'Supplemental -Highly Recommended'.
Table 2 provides a framework for selecting tools to assess chronic pain in children and young people with CP.The CP CDE pain tools were further sorted by pain categories and complemented by ICF representation to facilitate the practical application of the recommended valid and reliable tools.For example, to assess pain intensity, clinicians and researchers can select from the following tools: Body Diagram, Brief Pain Inventory Long and Short Forms, Faces Pain Scale -Revised, Numeric Pain Rating Scale, Pediatric Pain Questionnaire, and the Visual Analog Scale.The exact tool chosen for measuring chronic pain intensity in children and young people with CP would depend on multiple factors.For instance, the Brief Pain Inventory, Faces Pain Scale -Revised, and Numeric Pain Rating Scale are frequently used clinically to assess chronic pain as they are easy and quick to administer to children with all levels of mobility and culturally appropriate for use in international studies (Table 2).
For assessment of pain interference on activity and participation in children and young people with CP, the Bath Adolescent Pain Questionnaire, Brief Pain Inventory Long and Short Forms, Child Activity Limitations Interview, Child Self-Efficacy Scale -Child, Pain Interference Index, and the PROMIS Pediatric Pain Interference Scale are recommended options.Recommended options to assess the impact of pain on behavior in children and young people with CP include the Face, Legs, Activity, Cry, Consolability Scale, the Non-communicating Children's Pain Checklist -Revised, the PROMIS Pain Behavior Short Forms, and the Pediatric Pain Profile.
While no single pain tool addressed the impact of chronic pain in children and young people with CP using an ICF perspective, a combination of tools could be used.For a detailed description of each NINDS CP CDE pain tool, details on psychometric properties, and use in other NINDS disease groups, please link to each Notice of Copyright found in Table 2, the NINDS CDE website, or Appendix S6.
The recommended NINDS CP CDE pain tools incorporate a diverse set of measures to assess the impact of chronic pain compared with other condition-specific CDEs.

T A B L E 2 (Continued)
Pain Interference Short Forms found in the recommendations for myalgic encephalomyelitis/chronic fatigue syndrome.Finally, the Spinal Cord Injury -Pediatrics pain recommendations include the Child Activity Limitations Interview.
Examples of other pain tools in condition-specific NINDS CDEs excluded from further consideration and the reason(s) for exclusion are given in Appendix S7.
Table 3 shows the CP CDE pain tools categorized by agegroups, self-report versus proxy, and format of administration.This information can guide clinicians and researchers to identify the best measure(s) for their study or clinical setting.These identified chronic pain measures are directed at school-aged children and adolescents who can self-report pain.
Infants, toddlers, and non-verbal children with CP present a unique challenge in assessing pain.For studies targeting non-verbal children or children with communication challenges, recommended pain tools include proxy/caregiver report versions of the Bath Adolescent Pain Questionnaire, Child Activity Limitations Interview, Child Self-Efficacy Scale -Child, Pediatric Pain Profile, PROMIS Pain Behavior Short Forms, and PROMIS Pain Interference Short Forms.
Behavioral pain assessment tools such as the Face, Legs, Activity, Cry, Consolability Scale, the Non-communicating Children's Pain Checklist -Revised, and the Pediatric Pain Profile are appropriate for preschool-age children as well as children and young people unable to self-report pain.

Content gap recommended CP pain CDE tools
Few areas of functioning are underrepresented in the current recommended NINDS CP CDE pain tools; for example, tools that capture the impact of chronic pain on sleep pattern, coping responses to chronic pain, attitudes towards pain that are based on beliefs, or cultural and ethnic backgrounds.Although the proposed set does not include tools fully dedicated to these areas, a few of the tools partly cover some of them: for example, the Child Self-Efficacy Scale -Child (coping strategies) and the Bath Adolescent Pain Questionnaire (impact of pain on sleep).Future Face, Legs, Activity, Cry, Consolability revisions will consider expanding the content of the set to address these gaps.

DISCUS SION
This paper describes the first condition-specific chronic pain CDE measures for a pediatric population.The new CP CDE chronic pain tools address the evaluation of chronic pain and its functional impact in everyday activities in children and young people with CP, contributing to filling a gap in chronic pain assessment and evaluation in this population.The proposed chronic pain tools harmonize the assessment of chronic pain in these children and young people.The 15 recommended chronic pain assessments facilitate the evaluation of the location, intensity, quality, and behaviors of pain, as well as the interference of chronic pain in dayto-day activities in children and young people with CP.Most tools may be used in school-aged children, allowing them to self-report their experiences of living with chronic pain.Families, professionals, and researchers should consider this information to guide goal-setting and intervention strategies.
When comparing the content of the 15 recommended CP CDE pain tools with other initiatives assessing pain in CP, for example in terms of coverage of ICF components, 13 the CP CDE pain set ensures systematic evaluation of the impact of chronic pain in activities and participation.In addition, the proposed CP CDE pain tools cover the 12 domains suggested by Harvey et al. 17 as core areas guiding pain assessment in CP: pain location, pain frequency, pain intensity, changeable factors, impact on emotional well-being, impact on participation, pain communication, influence on quality of life, physical impacts, sleep, pain duration, and pain expression.These domains reflect the complexity of pain in a heterogeneous population such as those with CP, where communication impairments, intellectual disabilities, and medical comorbidities are common and impact significantly on the ability to self-report.
The importance of CDEs for research studies and metaanalyses has been clearly stated by the National Institutes of Health and research community (Sheehan et al. 2 and others), and they can also serve an important purpose in clinical practice.In addition to accelerating the pace of discovery for implementation into best practice guidelines, the CDEs can serve as a resource for practicing clinicians and trainees as a repository of validated measurement tools for evaluating prognosis or documenting patient progress over time.CDEs can facilitate communication between providers, which has been cited as a significant barrier to chronic pain management for children and adolescents with CP. 53 Furthermore, the set of CDE tools can be the basis of quality-improvement projects to standardize documentation and process where alignment between healthcare providers can harmonize with the scientific literature.
Clinicians or researchers can use Figure 1a as a guide to select appropriate tools for their intended study or clinical settings.Starting with the age category of the child(ren), where measurement is needed, they can then move to the decision-point diamond in the pain domain of greatest interest.There, the chart shows options for administration/report and lists available items.The larger list can be quickly narrowed to only the items most appropriate for a given situation.The chart demonstrates the relative paucity of tools for preschool-aged children, and that many of the instruments focus on the intensity domain.Importantly, the functional impact of chronic pain in everyday activities can be explored with tools categorized under pain interference.Figure 1b provides examples of the ICF content analysis that may be done for specific items of the tests (as summarized in Table 2), showing how items represent different ICF domains.Examples of the functional impact of chronic pain, using the ICF language, are shown in the component activities and participation.These summary tools can, like the CDEs in general, streamline the process of identifying appropriate measures in situations when it is important to assess chronic pain.
This study has limitations.By limiting the inclusion criteria to pain tools published in English, it excluded any pain tools published exclusively in another language.Future revisions might include broadening the inclusion criteria to pain tools published in non-English language.Another limitation is that studies assessing pain in children with CP use disease/disorder diagnostic pain tools; as such, many of the pain tools were not specific for children with CP or differentiated between types or motor functional levels of CP.Because we took a stepwise approach to facilitate identification and critical evaluation of tools within the biopsychosocial model of assessing chronic pain and its impact on function in children and young people with CP, some biopsychosocial factors were underrepresented, including those focused on coping.These are areas to be evaluated.
Similar efforts were leveraged to move towards implementation of these tools into research and clinical care. 19,21Given the high prevalence of chronic pain in the population of children with CP, 19 this set of CDEs provides the framework to begin collecting data immediately to supplement primary outcome measures of studies and to understand interactions between pain and response to interventions.Furthermore, the proposed CP CDE pain tools provide the data structure for studies for which chronic pain is a primary outcome measure.
Several content gaps were identified after comparison of chronic pain tools for children and young people with CP.There is a need for validated tools of chronic pain across the ICF framework for use with children and young people who are non-verbal or who have intellectual disabilities.Similar findings have recently been reported by Smith et al., 77 showing a scarce number of tools to assess chronic pain interference in individuals with CP who are unable to self-report owing to communication, motor, or cognitive limitations.
For tools that assess physical function and activity participation in relation to chronic pain, inclusion of assessments that measure activities across a spectrum of physical abilities is needed.There is also a need for assessments of types of chronic pain (e.g.neuropathic, visceral, central, and musculoskeletal).Finally, there is a need for validated measures that address change in chronic pain with interventions in children and adolescents with CP.
Although several tools exist, there are gaps in characterizing and assessing chronic pain in children and young people with CP.Tools that characterize and assess chronic pain across ICF domains, ages, and functional abilities in children and young people with CP must continue to be developed, validated, and utilized.However, it is critical that work moves beyond assessing chronic pain intensity.Tools validated for and sensitive to assessing changes in chronic pain across ICF domains in children and young people with CP are imperative for identification of promising interventions for improving chronic pain, initiation of clinical trials to provide the rigorous research needed to assess these interventions, and implementation of these interventions to reduce the burden of chronic pain in this population.Lastly, we acknowledge that the current proposed set underrepresents the functioning areas of impact of chronic pain on sleep pattern, coping strategies to stress and chronic pain, and attitudes towards pain that are based on beliefs, or cultural and ethnic backgrounds.A stepwise approach to critically evaluate and identify tools targeting these biopsychosocial factors and their impact on chronic pain in children and young people with CP is recommended.

CONCLUSION
This initiative addressed a content gap identified in the NINDS CP CDEs version 1.0.With the novel set of pain tools recommended, the CP CDE pain tools provide a framework for consistently measuring chronic pain in research and clinical studies involving children and young people with CP.As research evolves, updates and revisions to the CP CDEs are expected and welcomed to help improve the rigor of these data collection standards.Beyond research applications, this comprehensive set of CP CDE pain tools also serves as a clinical resource for teaching, standardizing the selection of pain measures and pain assessments, adopting a biopsychosocial approach to pain evaluation, harmonizing data collection and reporting, and guiding quality-improvement projects to further develop the care of children and young people with CP and chronic pain.
Of the 15 measures, the Brief Pain Inventory -Short Form tool is included in most of the condition-specific CDEs assessing chronic pain including Chiari I malformation, facioscapulohumeral dystrophy, neurorehabilitation, myalgic encephalomyelitis/chronic fatigue syndrome, multiple sclerosis, Parkinson disease, and Spinal Cord Injury -Pediatrics.The Spinal Cord Injury -Pediatrics recommends the Faces Pain Scale -Revised along with the PROMIS Pain Behavior and T A B L E 2 CP CDE pain tools.

T A B L E 3
Age, report type, and format of pain tools.