The economic impact of living with a rare disease for children and their families: a scoping review protocol

Background Rare diseases are an often chronic, progressive and life-limiting group of conditions affecting more than 30 million people in Europe. These diseases are associated with significant direct and indirect costs to a spectrum of stakeholders, ranging from individuals and their families to society overall. Further quantitative research on the economic cost for children and their families living with a rare disease is required as there is little known on this topic. This scoping review aims to document the extent and type of evidence on the economic impacts of living with a rare disease for children and their families. Methods This scoping review will follow the PRISMA-ScR and Joanna Briggs Institute guidelines and follow the six-stage methodology for scoping reviews: (1) identifying the research question, (2) identifying relevant studies, (3) study selection, (4) charting the data, (5) collating, summarising and reporting results and (6) knowledge user consultation. Key inclusion criteria have been developed according to the Population-Concept-Context (PCC) framework. The databases EconLit, ABI/Inform, MEDLINE, PubMed, CINAHL, and Scopus will be searched for possible articles for inclusion. Two independent reviewers will screen titles and abstracts of potential articles using a dual review process to ensure all relevant studies are included. All included articles will be assessed using a validated quality appraisal tool. A panel of patient and public involvement representatives experiencing rare diseases and knowledge users will validate the review results. Conclusions This scoping review will map the current literature on the economic impact of paediatric rare diseases to understand how these impacts affect children living with rare diseases and their families. This evidence has the potential to influence policy and future research in this area and will support further research on the economic impact of rare diseases on families.


Amendments from Version 1
Following recommendations from the peer reviewers of Version 1 of this scoping review protocol, the following changes have been made.The introduction has been edited for clarity, and the contribution of the scoping review to the literature has been highlighted.The research question has been amended to reflect the aims of the review better.The Consolidated Health Economic Evaluation Reporting Standards 2022 (CHEERS 2022) will be used to assess the quality of the included studies instead of the Mixed Methods Appraisal Tool (MMAT).Further detail is provided on the PPI representatives' and knowledge users' roles in this review, including their relationship with the authors and the stages at which they will be involved in the review.An additional table provides examples of direct and indirect healthcare and nonhealthcare costs that will be included in the review.The types of sources to be included in the review have been further clarified.The data extraction table has also been updated to reflect the reviewers' recommendations to include the types of costs and healthcare systems reported by the articles information on the data extraction process has been provided, including which authors will be involved.Rare diseases will be defined according to Orphanet classifications, which have been cross-referenced across contexts and databases and should be acceptable across any contexts included in the review.The likely issue of high heterogeneity will be addressed in the review according to the results of the included articles.The empty PRISMA-ScR (previously Figure 1) has been removed.The mention of a ' costminimal' intervention has been removed.The results of this review will instead inform further research on this topic.

Introduction
The collective incidence of rare diseases contributes to a significant global population that belies its 'rare' title.It is estimated that there are between 6,000 and 8,000 known rare diseases (European Commission, n.d.;Kruse et al., 2022) that affect 3.5%-5.9% of the global population (Nguengang Wakap et al., 2020).Rare diseases are often incurable, complex and are associated with a high social and economic burden that reaches from the patient to society (García-Pérez et al., 2021;Somanadhan et al., 2023a).Approximately 70% of rare diseases start in childhood, and early diagnosis and treatment is critical to prevent disease progression and avoid adverse health outcomes, including disability and death (Morton et al., 2022).
Eighty percent of rare diseases have a genetic component and therefore treatment is often limited or costly, and 95% of rare diseases lack an approved treatment (Somanadhan et al., 2023b).This brings challenges regarding funding for research and development and treatment accessibility, as orphan drugs, which are developed specifically for rare diseases, can cost up to five times more than non-orphan drugs (Chambers et al., 2020).Few rare diseases have orphan drugs, contributing to a large unmet need (Rodriguez-Monguio et al., 2017).Other treatments for rare diseases, such as gene therapy, which involves modification of genes to treat, prevent or cure an illness or disease (White, 2019), similarly come at a high cost and are limited.
The lack of funding for orphan drug development stems from the limited market potential of rare diseases, as developing drugs for limited patient groups is unlikely to be cost effective for pharmaceutical companies (Iizuka & Uchida, 2017).However, this has both human and economic costs.High prices and reduced access to treatment can cause increased health burden and premature death for patients with rare diseases; lack of treatment access also reduces rare disease patients' capacity to engage in society independently, incurring costs such as loss of income tax, absenteeism and presenteeism of carers, and potential increased healthcare costs due to the consequences of poor health (Hyry et al., 2013).
Given the incurability of many rare diseases, as well as the lack of treatment plans, most of the costs associated with rare diseases can be attributed to care management or supportive therapies.Cost-of-illness studies can be used to estimate the direct, indirect and associated costs of living with a rare disease, as well as the impact of rare diseases on healthcare resources and labour productivity (Larg & Moss, 2011).Other methods of determining economic burden are economic evaluations, which analyse costs and outcomes of interventions to determine cost-effectiveness (Goodacre & McCabe, 2002).Direct costs are the healthcare and non-healthcare costs for which the health system, society, family and individuals with the illness are directly accountable for, whereas indirect costs are associated with productivity losses due to morbidity and mortality that indirectly impact the individual, family, society or employer (Jo, 2014).Economic costs associated with rare diseases arise from both direct healthcare costs, including those of specialised healthcare service provision, direct non-healthcare costs, such as those of care or education services, and indirect costs, such as loss of income at an individual level and loss of productivity on a societal level (Chung et al., 2023;Zurynski et al., 2008).Incidence of disease, resultant impacts on morbidity and quality of life, and financial consequences (direct or indirect) due to disability, injury or premature mortality are all approaches that can be explored through cost-of-illness studies (Jo, 2014).While cost-of-illness and economic evaluation studies can be useful in determining economic impacts of interventions, the variety of approaches for conducting these studies means that the literature around this topic lacks standardisation.
Studies have been performed to estimate the burden and healthrelated quality of life for all patients (including children) with rare diseases, such as the Social Economic Burden and Health-Related Quality of Life in Patients with Rare Diseases in Europe (BURQOL-RD) study, which considered eight EU countries (Bulgaria, France, Germany, Hungary, Italy, Sweden, Spain, UK) (López-Bastida et al., 2016); and the National Economic Burden of Rare Disease study, commissioned in the US by the EveryLife Foundation (Yang et al., 2022).These studies both found a significant economic impact of rare diseases due to their high collective prevalence and high per-person costs, generated either through loss of labour productivity or the cost of formal or informal care.Children with rare diseases have been associated with higher economic costs; in the US, per-person direct costs are most expensive in childhood and decrease with age; similarly, per-person indirect costs for children are higher than for adults, due to absenteeism, presenteeism and social productivity losses of family caregivers (Yang et al., 2022).In Hong Kong, children with rare diseases were also found to experience higher per-person direct and indirect costs due to experiencing a higher cost of healthcare services, medical resources, informal care support and special education (Chung et al., 2023).Similarly, families of children living with rare diseases in Spain were identified as having poorer financial situations than families of adults with rare diseases, due to the eligibility of adults for benefits such as treatment allowances or pensions, which are not available for children (Gimenez-Lozano et al., 2022).These disproportionately higher per-person costs for children have a significant impact on families.Capturing the evidence on this economic impact can aid policy makers in their decision-making, inform resource allocation and lead to the development of solutions that can benefit people living with rare diseases and their families (Yang et al., 2022).However, the economic impact of rare diseases is somewhat neglected within the rare disease literature compared to other areas, e.g., clinical research, likely due to the heterogeneity and low individual incidence of rare diseases.Apart from the studies discussed above, few cost-of-illness studies specifically related to children have been performed, and those that exist tend to focus on rare diseases for which a specific treatment exists (e.g., cystic fibrosis) (Angelis et al.,2015).Previous scoping reviews in general have found a lack of studies on the economic impact of rare diseases (Delaye et al., 2022;García-Pérez et al., 2021).
The goal of this scoping review is to map existing studies on the economic impact of living with a rare disease for children and their families, examine the current methodologies for collating and reporting the evidence of these impacts, and to identify any potential gaps in the literature.It examines the types of direct and indirect impacts that are evaluated in the literature, and how they are measured and analysed.This study does not conduct a meta-analysis to determine the average monetary impact of rare diseases found across studies; rather, this review focuses on a family economic perspective, considering rare diseases amongst paediatric populations.To the author's knowledge, it is the first scoping review with this focus.

Methods
The proposed systematic scoping review will be conducted in accordance with the updated JBI methodology for scoping reviews (Peters et al., 2020b) and recommendations from Levac et al. (2010), which build on previous existing methodological guidance (Arksey & O'Malley, 2005;Peters et al., 2015).A six-stage process, including knowledge user consultation as a final stage, will be employed throughout the review process and has been used in the development of this scoping review protocol.An overview of each stage is presented below.Section headings are taken from Levac et al. (2010).
Reporting will be guided by the Preferred Reporting Items for Systematic Reviews and Meta Analyses Scoping Review extension (PRISMA-ScR) checklist, to ensure compliance with up-to-date PRISMA reporting guidance.This extension was developed to improve the methodological and quality reporting of scoping reviews (Tricco et al., 2018), and will assist in the formulation of the review and an informal quality assessment.
The review will be conducted as part of a wider project with input from four patient and public involvement (PPI) representatives from the rare disease community, and six knowledge users working in the rare disease field already linked with the project will validate the results and their presentation.This is according to the guidance on knowledge user engagement developed by Pollock et al. (2022).Relationships with the knowledge users and PPI representatives were established prior to the commencement of this review via the Rare Disease Research Partnership (RAinDRoP) (Somanadhan et al., 2020).This protocol has been developed with and reviewed by knowledge users and PPI representatives to inform the research questions and search strategy, as per the knowledge user engagement guidance (Pollock et al., 2022).Further information is provided in the relevant section of this protocol (Stage 6: Consultation).

Research question
This scoping review aims to identify, appraise and reliably map current literature on the economic impacts of living with rare diseases for children and their families, and identify the screening and assessment tools used to identify these impacts.Therefore, the research question is "how is the economic impact (direct and indirect costs) for families and caregivers of children with a rare disease identified and measured in the literature?".
The research objectives of this scoping review are: 1. To identify, appraise, and synthesise knowledge surrounding the economic impacts of rare diseases affecting children and their families through consideration of healthcare and non-healthcare direct and indirect costs.
2. To understand how these costs are measured.

3.
To clarify what specific disease populations and disease characteristics are most researched.
4. To determine the study settings, rare conditions and geographical contexts, and the study types and organizations involved (e.g., charitable organisations, pharmaceutical companies, etc.).
5. To highlight any gaps in the literature on the economic impact of rare diseases on children and their families.
As scoping reviews summarise particular topics, the research questions are typically broad with a specific scope of inquiry, indicating the focus of the study (Levac et al., 2010).Therefore, the following sections explain the Population-Concept-Context (PCC) framework (Peters et al., 2020a) used to formulate the research questions for this study, to illustrate the origins of the research questions and the search strategy.

PCC Framework Population
This scoping review focuses on the economic impact of having a child with a rare disease on family units, recognising that children will not bear the economic burden of living with a rare disease themselves.Therefore, studies that consider the economic impact from the perspective of families, parents, (informal) caregivers that are part of the family unit or guardians will be included.This includes the direct and indirect impacts of having a child with a rare disease which commonly affect family members.

Concept
The concept is the economic impact of rare diseases for children and/or their families.This is assumed to mean any financial costs directly or indirectly incurred due to the rare disease.The types of direct ad indirect costs that will be included in this review have been identified (Delaye et al., 2022;Fautrel et al., 2020;Liljas, 1998) and are included in Table 1.
How these effects are measured (e.g., using validated screening or measurement tools) will also be mapped.The economic impact of rare diseases is typically assessed through cost-of-illness studies or economic evaluations, as these studies explore the impact of illnesses or diseases via their associated costs (García-Pérez et al., 2021).Therefore, these types of studies are highlighted in the search strategy.Other studies, e.g., intervention or health impact studies that discuss economic burden or impact for families, are also captured in the search strategy.

Context
The context differs to the population, as this scoping review will focus on the phenomenon of children with rare diseases.Therefore, the context is rare diseases in childhood, and is thus divided into two parts.The first centres around the definition of 'children'.The United Nations Convention on the Rights of the Child definition is used to understand a 'child' as anyone under the age of 18 years (UNICEF, n.d.).Other relevant terms, such as adolescent, infant and variations on these are included to capture relevant literature.Studies that discuss siblings will also be included, to reflect the impact of living with a rare disease on this population.
The second part of the context of this review considers rare diseases.For the purposes of this review, conditions that are classified as rare by Orphanet will be considered rare diseases.This inventory is cross-referenced with international terminologies and reference databases (Orphanet, 2020) and should therefore help the classification of conditions between the included studies, or in studies that include multiple contexts.
Studies that consider individual rare diseases will be included; however, studies that consider chronic or complex conditions that are not rare will be excluded.Studies that discuss a range of complex conditions, including rare disease(s), will be included if they clearly delineate their results and data can be charted according to the rare disease(s) considered.Due to variation in definitions, illnesses or diseases that are conceptualised as rare diseases by researchers in particular countries where these diseases are considered rare will be included, even if different to the authors' home country.For example, sickle cell disease is considered rare in the Republic of Ireland but is the most common genetic condition in the world (Rare Disease Taskforce, 2020).

Types of sources
All study designs, whether quantitative and qualitative, will be considered.Studies of any design that provide information  Fautrel et al. (2020); Liljas (1998) on the economic costs (direct and/ or indirect) of paediatric rare diseases and meet the inclusion criteria will be included.This will include both experimental and quasiexperimental study designs such as randomised controlled trials, non-randomised controlled trials, before and after studies and interrupted time-series studies.Analytical observational studies including prospective and retrospective cohort studies, case-control studies and analytical cross-sectional studies will also be considered for inclusion, as will descriptive observational study designs including case series, individual case reports and descriptive cross-sectional studies.
Qualitative studies will also be considered including, but not limited to, designs such as phenomenology, grounded theory, ethnography, qualitative description, action research and feminist research.
Studies that are not primary research, e.g., reviews or conference materials, or non-peer-reviewed articles, e.g., dissertations or theses, will be excluded, as will studies that have not been peer-reviewed.A publication date limit of 1983 until the present will be applied to ensure relevance to current economic contexts.The start date of 1983 reflects the introduction of the United States Orphan Drug Act in the same year, which aimed to advance development of drug treatments for rare diseases and thus stimulated research in this area (Dawkins et al., 2018).There are no limits on geographical location.Articles in languages other than English will be excluded due to lack of funding for translation services; however, this restriction will not be imposed on the search strategy, and it may be reviewed if there are a small number of results in another language, to reduce the possibility of language bias (Stern & Kleijnen, 2020).If results are excluded due to language, the reasoning for this will be reported.The corresponding authors of articles for which the full-text is not available online will be contacted to source a copy of the article; however, if it is not possible to retrieve the full-text, the article will be excluded.The inclusion/ exclusion criteria are presented in Table 2.
Stage 2: Identifying relevant studies Databases to be included in this scoping review were chosen to reflect the nature of the research questions.Therefore, the databases searched will include EconLit (EBSCO), ABI/Inform Global (Proquest), MEDLINE (Ovid), PubMed, CINAHL Plus, and Scopus (Elsevier).
The search strategy was developed by the primary author in consultation with a university librarian.An initial search was performed on 13 March 2023 to establish common terms and subject headings relevant to the topic.These terms and headings were used to develop the search strategy.Boolean operators, and truncation markers will be used in the full search strategy, which will be altered to meet the requirements of each database.A sample search strategy is provided in Table 3.This search strategy is subject to change during the review process, as the reviewers become more familiar with the literature (Peters et al., 2020a).

Stage 3: Study selection
Studies yielded by the search strategy will be uploaded to End-Note 20 (Clarivate Analytics, 2023) and duplicates will be removed.The remaining articles will be screened by title and abstract first, followed by a full-text review to determine their suitability for inclusion in the review.This part of the proposed review will be supported through the use of Covidence, a web-based collaboration software platform that streamlines

Population
Studies that discuss costs of rare diseases to the family unit, including parents, informal caregivers and/ or guardians.
Studies that only focus on populations outside the family unit, e.g., caregivers or guardians not related to the child with a rare disease (e.g., formal/ professional caregivers), healthcare providers, healthcare systems, society.

Concept
Studies that discuss the economic impacts of having a rare disease on children and their families, including direct and indirect impacts.
Studies that discuss the impacts of rare diseases on children and their families, but do not focus on economic impacts.

Context
Any geographical location.
Studies that focus on rare diseases in childhood.
Studies that do not differentiate their study population between children or adults.
Studies that discuss complex or chronic conditions that are not rare diseases.

Language
Articles in English.
Articles in languages other than English.
Publication Date 1983 to present.Articles published prior to 1983.

Types of Evidence Sources
Peer-reviewed cost-of-illness studies, economic evaluations or other studies that discuss the economic impacts of living with a rare disease for children and their families.Peer-reviewed primary research sources e.g., research studies.
Secondary research sources, e.g., reviews (systematic, scoping, meta-analyses, etc.).Conference materials, editorials, commentaries, opinion papers, dissertations/theses. Studies for which the full text is not available following contact with the corresponding author.Non-peer-reviewed research.
the production of systematic and other literature reviews (Covidence, n.d.).Screening will be performed by the primary author and another independent reviewer and validated through peer debriefing.Disagreements on whether to include or exclude articles will be addressed by a third researcher.A pilot test will be completed with a sample of studies (n=25) to ensure consistent decision-making between the reviewers and the clarity of the inclusion and exclusion criteria, and facilitate possible necessary refinements, as recommended by the JBI Manual for Evidence Synthesis (Peters et al., 2020a).
Following title and abstract screening, included articles will go through a full-text review to determine their inclusion eligibility according to the inclusion/ exclusion criteria.As in the previous study selection step, this will be conducted by the primary author and another independent reviewer and validated through peer debriefing, with any disagreements resolved by a third researcher.Reasons for exclusion of sources of evidence at full text that do not meet the inclusion criteria will be recorded and reported in the scoping review.
As discussed in the previous section, authors of papers will be contacted to request missing or additional data, where required.The reference lists of included articles will also be searched to identify other potential studies not captured by the search strategy, and these will undergo a similar full text screening process by two researchers.
The actions of screening and full-text review will be reported according to the PRISMA-ScR guidance (Tricco et al., 2018) 4) will be trialled at the pilot test stage and will be modified and revised as necessary both prior and during the process of extracting data from each included evidence source.This table has been developed using guidance from the JBI Manual for Evidence Synthesis (Peters et al., 2020a) and amended to the focus of the proposed scoping review.Modifications will be detailed in the scoping review.The data extraction will be completed by the first author (NB) and audited by the last author (SS).Any disagreements that arise between the reviewers will be resolved through discussion, or with an additional reviewer/s.
Knowledge users and PPI representatives will be provided the opportunity to participate in Stage 3 and Stage 4 of the scoping review process.If interested in participating, they will receive training on the software used for data screening and extraction.
Stage 5: Collating, summarising and reporting the results Data charting will be completed using Covidence and will be shared among the team for review and sign off.The results of the review will be presented as a map of the data from the included studies according to the aims of the review, as recommended by the JBI Manual for Evidence Synthesis (Peters et al., 2020a).This will involve two aspects: reporting of the overall results, which will be presented in tabular form and include aspects such as number of studies included, types of study design, etc; and a basic descriptive analysis, which will apply meaning to the results (Levac et al., 2010).Lead author contact details Details of the lead or corresponding author in case contact is required for additional data or clarification.

Rare Disease
What type of Rare Disease is discussed.

Country
Country in which the study was conducted.

Characteristics of Included Studies
Aim of study What the source set out to do.

Description of Health System
The type and description of the health system relevant to the source.

Methodology
The research design and procedures or techniques used to identify, select, process, and analyse the data obtained by the authors.

Population Description
The sample used within the source, including characteristics e.g., size, age, gender, etc.

Inclusion Criteria Inclusion criteria for participation in the study
Exclusion Criteria Criteria that excluded potential participants from participating in the study Total number of participants How many participants were involved in the study.

Baseline population characteristics
Gender, Race/ Ethnicity, Age, etc. in tabular format.

Economic Impacts
Impact -Direct and Indirect What economic impacts were discussed by the source, and how these were measured, categorised into direct and indirect impacts (tabular format)

Interventions
Where the source discusses the introduction of an intervention, what type of intervention it was, its comparator and the details of its introduction.
Other Key Findings Any other key points related to the scoping review research questions.
Thematic analysis will not be undertaken as it is outside the remit of scoping reviews (Peters et al., 2020a); however, a table according to the PAGER framework will be provided.This framework, which looks at the patterns (P), advances (A), gaps (G), Evidence for practice (E) and research recommendations (R), provides a consistent approach for the reporting of scoping review findings (Bradbury-Jones et al., 2022).The analysis methodology will be reported to ensure transparency and rigour in the analysis process and assist in future replication.
The results of the review will be validated through peer debriefing and PPI representative and knowledge user consultation, discussed in the next section.Gaps in the literature will be highlighted as areas for future research.
High levels of heterogeneity between contexts, impacts and diseases are anticipated.Reporting of the impacts and costs incurred by rare diseases in the included studies will depend on and be influenced by the rare diseases and various other factors, such as access to health services and social assistance.Results will be reported according to country (to reflect the differing health systems and socio-economic contexts) and according to disease groupings.Rare diseases will be categorised according to Orphanet groupings, which group rare diseases according to relevant medical specialties (Rare Disease Research Landscape Steering Group, 2023).

Stage 6: Consultation
This review will include consultation with two groups: PPI representatives and knowledge users.The PPI representatives include two mothers and two fathers who are parents of children and young people with rare diseases and who have experience with the economic impacts of rare diseases for families with single and multiple children with rare diseases.These PPI representatives are active in the rare disease community and were involved in the conceptualisation of the overall project.
The knowledge users linked with this study include medical paediatric consultants, policmakers, and representatives of advocacy organisations all working in the rare disease field.For the purposes of this review, a knowledge user is defined as: "one in a position of authority to influence and/or make decisions about health policy or the delivery of services and can act to ensure that the findings of the research will be translated to influence decision making and change within their (or other) organisations" (Health Research Board, 2023, p.7).
This scoping review protocol was presented to the PPI representatives and knowledge users working in the rare disease field and the research questions and search strategy were validated through separate discussion and consultation to understand the priorities of the two groups.Following completion of the data analysis of this review, the results of the review will be presented to the PPI representatives and knowledge users for validation and to ensure the implications of the findings are meaningful to their community.Feedback from the groups will be reported in and incorporated into the final review.
Dissemination of the research findings will also be developed through knowledge user engagement.The same knowledge users and PPI representatives will be invited to participate in the development of an evidence summary for dissemination on social media.This is to ensure knowledge translation and impact is accessible and meaningful to the communities it is targeted at and is in line with the guidance for knowledge user engagement developed by Pollock et al. (2022).
As the PRISMA-ScR tool currently does not include the reporting of knowledge user engagement (Pollock et al., 2022), the participation of knowledge users in the consultation process will be reported using the ACTIVE framework, developed by Pollock et al. (2019) for use in systematic reviews.This framework is appropriate for use in this review due to the similarities in conduct processes between systematic and scoping reviews (Pollock et al., 2022).

Dissemination
The proposed scoping review will be submitted for publication in peer-reviewed academic journals.As previously discussed, an evidence summary will be developed for social media through knowledge user engagement, to ensure the meaningful transmission of results.In addition, the results will be presented at conferences and shared with relevant stakeholders and policymakers where appropriate.

Study Status
This review is currently in the stage three: study selection phase.Database searches have been performed and the results are being screened by title and abstract by two reviewers.

Conclusions
Rare diseases are associated with significant economic impacts for families of children living with rare diseases; however, the literature in this area is sparse and as a topic, it remains underexplored.The results of this scoping review will map existing work on the economic impacts of living with a rare disease for children and their families, contributing to the literature on this topic.The results will also be used to develop a survey that will measure the economic and psychosocial costs of living with a rare disease in Northern Ireland and the Republic of Ireland.

Genevieve Currie
School of Nursing and Midwifery, Mount Royal University, Calgary, AB, Canada Thank you for the opportunity to provide this review.This is a strong scoping review protocol paper.However, I have highlighted some things I think you could still focus on with in your paper to make your paper stronger.Please do not use the word patient to describe a person with a rare disease.Use the word person or child instead as you are not describing someone receiving an intervention or care in this manuscript. 1.
You could also include as therapy as direct costs therapy for children with rare diseases (physio, occupational, speech and behavioral), educational supports with aides and educational assistants and indirect costs for parents could be respite for caregiver support.I see some of these in table one but in the literature review these are not mentioned.

2.
Since this scoping review is focused on children and their families, I think this should be explicitly stated early in the third paragraph of the literature review.The manuscript also describes costs for adults with rare diseases but this should be only for context and not figure so prominently in the literature review as this is not the focus of this paper.

3.
I don't understand research question #4: "To determine the study settings, rare conditions and geographical contexts, and the study types and organizations involved (e.g., charitable organisations, pharmaceutical companies, etc.)."What do you mean by determine study settings?Are you asking to determine where other research studies have occurred and who was studied and who was involved in conducting the study?Just needs to be clearer.You could use the concepts you list under table 4 with charting the data.

4.
You mention indirect costs to siblings in the context.I think you could add siblings earlier in the background when you say children and their families, including siblings as they are in important family members to understand the impacts.

5.
Consultation: Will the PPI parents be parents of the same child i.e. a mother and father of the same child?I think it would increase diversity of the consultation if they were 4 parents of 4 different children.This could be stated in this section.
I would put this sentence earlier in the manuscript under methods to demonstrate you had 2. engagement with representatives much earlier than the consultative stage: "This scoping review protocol was presented to the PPI representatives and knowledge users working in the rare disease field and the research questions and search strategy were validated through separate discussion and consultation to understand the priorities of the two groups."Well designed and supported from multiple frameworks and theories.

3.
Excellent to include parents as consultants as well as knowledge users.Great to give the definition of a knowledge user that you are using.

Andrew Dwyer
Boston College, Massachusetts, USA Buckle and colleagues present a protocol for a scoping review that aims to map the current literature on the economic impact of pediatric rare diseases.Specifically the scoping review will examine how costs for pediatric rare diseases have been explored, what approaches have been employed, and what gaps remain in our understanding of the economic impact of rare pediatric conditions on families.This is a timely and important topic that merits investigation.A relative strength of the protocol include the rigor of the approach.Authors propose to: follow the PRISMA-ScR guidelines to guide the process, utilize the PCC model to guide article identification, search 6 databases, use supporting software (EndNote, Covidence) and have public and patient involvement (PPI).After carefully reviewing the protocol I have a number of questions that I feel merit consideration: Authors appropriately cite the PRISMA-ScR yet I feel it would be useful to consider using an economic evaluation guideline from the EQUATOR network (i.e., CHEERS reporting guideline) to aid in identifying gaps in the literature and guide future reporting efforts for consistency and comparability. 1.
The protocol describes cost of illness analysis as well as direct and indirect healthcare costs.Given that rare disease patients are geographically dispersed and have difficulty accessing specialized care I feel that noting travel costs is a relevant and key consideration.

2.
The protocol cites recent economic evaluations for rare diseases (i.e., Delaye et al., 2022 andGarcia-Perez et al., 2021) yet it is not completely clear how the proposed scoping review will 3.
differ from the recent analysis or what gap this study will fill.Did these prior studies include (at least to some extent) a focus on pediatrics?This could be clarified for precision.
I applaud the PPI but there is relatively scant description of this.Have PPI stakeholders already been identified?If so, who are they and what perspectives do they bring?Similarly, it is not exactly clear at what stages they will be involved.Having a separate section detailing PPI would be beneficial.Similarly, who are the "knowledge users in clinical practice and policy" stakeholders?4.
When describing the population the term "economic impact" is not clearly defined.Is it direct costs?Indirect costs?Both?Other?Please clarify for precision.

5.
The protocol correctly states that definitions of what makes a condition rare varies by country.I would appreciate more clarity on how rarity will be defined.Presumably by the country the investigators hail form.How will this be handled in international (cross-border) collaborative studies?6.
Under "types of sources" it is stated that "Results excluded due to language will be reported transparently".This seems vague, please clarify.

7.
I was confused by the inclusion criteria.Shouldn't this include an inclusion criteria specifying articles that report on healthcare costs for rare diseases? 8.
The "Stage 2: Identifying relevant studies" was not entirely clear.I understand that titles and abstracts as well as full text will undergo independent dual review.Will data extraction also be independently done by two investigators then compared? 9.
In the section on "Stage 5", what does the sentence "Explicit details of the methodology for analysis will be provided to ensure transparency and rigour in the analysis process"?Would not this be part of the quality appraisal?Please clarify.

11.
In Table 3, health finance and healthcare system structures vary widely between countries.For example, the U.S. has health insurance tied to employment with largely a fee-for-service structure, while the U.K. has nationalized healthcare (i.e., NHS) and Switzerland has a mandatory insurance program.I feel that it is important to extract and describe information on the respective health systems.12.
In the conclusions section it would be helpful to operationally define terminology that is introduced.Specifically, what is a "cost-minimal intervention"? 13.
Is the rationale for, and objectives of, the study clearly described?Yes

Are sufficient details of the methods provided to allow replication by others? Partly
Are the datasets clearly presented in a useable and accessible format?

Not applicable
Competing Interests: No competing interests were disclosed.
Reviewer Expertise: Rare diseases I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above.
healthcare costs.We acknowledge the reviewer's concerns around stage 5 of the review.As this is a scoping review, the method of analysis will not be as in-depth as a systematic review or metaanalysis.However, the analysis methodology will be reported to ensure transparency and rigour in the analysis process and assist in future replication.

Yvonne Zurynski
Professor of Health System Sustainability, Macquarie University, Sydney, New South Wales, Australia An interesting protocol for a scoping review.
The introduction is excessively long and reads like a literature review for a thesis rather than the background for a peer-reviewed publication.I would suggest shortening the background to include a very clear rationale that supports the need for this scoping review.
In the abstract, the authors mention that the review will support a cost-minimal interventionthere is no rationale provided as to why this might be suggested before the review has even been done!If you are going to use terms such as "cost-minimal" these need to be clearly defined.
I would suggest that the main research question is revised to include how the economic impacts are measured, the types and magnitude of these impacts rather than just how impacts are "identified".
The methods rely on the JBI 6-step process and PRISMA-ScR which is a good basis for this type of review.
The involvement of patient and public is commendable, however, it's not clear whether the PPI panel has already been established, what kinds of representatives are included in the PPI and exactly how they have contributed to the development of this protocol -some additional clarification would be good to include.
In the methods please provide clear definitions of direct and indirect costs that will be included and/or excluded in the review, is loss of income included or excluded?Is travel to appointments included or excluded?What about the cost of medical equipment (wheelchairs etc.) and medical consumables (e.g.dressings, oxygen tubing and masks, etc...).
Please be clear on what study designs are included and excluded -for example the methods say that "case-control studies and analytical cross-sectional studies will also be considered" -it's not clear what this means -will you include such studies or exclude them?Justification to use the MMAT tool is required.Why are you not using quality assessment tools specifically developed for health economic studies e.g.CHEC, QHES or HEE?
Stage 5 seems to have been a little glossed over when actually this is extremely important for a review such as this.It is very likely that there will be high levels of heterogeneity among the included studies and yet this is not addressed.For example the economic outcomes and impacts are likely to differ depending on the country of origin and factors such as the degree of universal coverage, access to private health insurance and social security supports will need to be considered -how will you deal with these very different socio-economic contexts?What exactly is meant by "financial experiences"?
There is likely to be a significant level of heterogeneity of rare diseases included in the identified studies -what will be the strategy for interpreting the economic impact for families who have a child with for example a developmentally disabling disease such as Rett Syndrome compare with for example Fabry disease where the impacts are different?
Including an empty PRISMA chart as a figure holds little value for the reader of this protocol.I would suggest that the authors think through a little bit more carefully about what details they may wish to extract in their data charting to ensure that they extract adequate detail for synthesis and interpretation.
Is the rationale for, and objectives of, the study clearly described?Yes

Is the study design appropriate for the research question? Partly
Are sufficient details of the methods provided to allow replication by others?aim to evaluate the economic impact of each rare disease, but rather understand what types of costs are evaluated in the included studies.The likely high levels of heterogeneity will be addressed following data extraction and analysis according to the articles retrieved.The data extraction table will include the country of origin of the articles, the rare diseases evaluated by the articles, and the types of costs evaluated by the articles, therefore allowing the mapping of these types of costs according to country and disease.

4 .
Is the rationale for, and objectives of, the study clearly described?PartlyIs the study design appropriate for the research question?YesAre sufficient details of the methods provided to allow replication by others?YesAre the datasets clearly presented in a useable and accessible format?YesCompeting Interests: No competing interests were disclosed.I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.Reviewer Report 13 April 2024 https://doi.org/10.21956/hrbopenres.15178.r39074© 2024 Dwyer A. This is an open access peer review report distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Andrew Dwyer Boston College, Massachusetts, USA The authors have responded appropriately to the points raised in the initial review.Is the rationale for, and objectives of, the study clearly described?Yes Is the study design appropriate for the research question?Yes Are sufficient details of the methods provided to allow replication by others?Yes Are the datasets clearly presented in a useable and accessible format?Yes Competing Interests: No competing interests were disclosed.Reviewer Expertise: Rare diseases I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.Version 1 Reviewer Report 24 October 2023 https://doi.org/10.21956/hrbopenres.15057.r36287© 2023 Dwyer A. This is an open access peer review report distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.