1. Context
Adolescents (10–19 years) are 18% of the world population [1]. Or about one billion of the world’s population, with 70% living in developing countries [2]. Adolescents are at high risk of Sexual and Reproductive Health complications (SRHs), such as early childhood marriage, pregnancy in adulthood, unsafe abortions, Sexually Transmitted Infections (STIs), HIV (Human Immunodeficiency Virus), AIDS (Acquired Immunodeficiency Syndrome), and other life-threatening sexual health problems [3]. Adolescent childbearing is associated with adverse health outcomes for both the adolescent mother and the infant [4]. Among 15 to 19 years old people, nearly a quarter of women with a history of sex and more than a third of men with sex experience have not received any reproductive health services. Low rates of reproductive health care among adolescents warn us that preventative, diagnostic, and treatment services are necessary for providing healthy sexual and reproductive behaviors [5, 6].
Teenagers need services that improve their physiological, cognitive, emotional, and social alteration into adulthood [7, 8]. According to the 2001 World Health Organization (WHO) recommendation on adolescent friendly health services, the purpose of SRH services for adolescents must be comprised at least one of the following goals: (i) providing the environment and conditions for adolescent support; (ii) providing the level of knowledge, attitudes, skills, and behaviors for reproductive health; and (iii) increasing the use of health services [9]. The WHO guidelines for providing Youth Friendly Health Services (YFHS) recommend services that are accessible, acceptable, equitable, appropriate, and effective [10]. Equity of services refers to the right of all adolescents to acquire quality services. Other domains denote how health services should be provided to teenagers [11]. According to the previous study, the acceptability of health care can only be measured by obtaining adolescents’ views and attitudes [12].
Adolescence is a period of vital changes. Preventive measures in the field of health and social structures are necessary to promote the health of adolescents [13]. Although adolescents are at high risk of unwanted consequences of sexual behaviors, they are less likely to seek reproductive health services due to numerous barriers [14]. In 1999, Senderowitz reported four reasons that adolescents avoid using SRH services: (i) policy constraints, (ii) work barriers (hours of working, transportation, cost), (iii) lack of information, and (iv) feelings of discomfort (the belief that services are not for them, concern about aggressive staff, fear of medical procedures., etc.) [15].
The primary study describes that barriers to the provision of YFHS were lack of youth-friendly training among staff and lack of a dedicated space for young people. Four of the eight facilities did not appear to uphold the right of young people aged 12 years and older to access healthcare independently. Breaches in young people’s confidentiality to parents were reported too [4]. A review of empirical studies describes barriers to using reproductive health services among youth and young adults in four categories: (i) service access (e.g. ease and knowledge of access); (ii) service entry (e.g. wait time, clinic comfort); (iii) quality of services (e.g. perceived lack of respect); and (iv) social causes (e.g. embarrassment, being recognized, being gossiped about, and confidentiality) [16]. Another study reported similar perceived barriers among school-aged and male youth [17].
Youths who are living in South Africa are facing multiple barriers to accessing sexual health services. These barriers include their information is not kept confidential; as a result, their privacy will not be remained safe, they should wait for long periods to receive services (often with adults from the same community), inappropriate hours of work, where they live from clinics, and fears that their families understand their visit and going to the clinic [18]. In another study, adolescents’ concerns for pursuing health services were fear and shame of community reflection, the confidentiality of their information, parental control, and the preference for seeking qualified and trained health care professionals [19]. On the other hand, health professionals tend not to provide counseling to adolescents, especially at peak times. Clinic placement and work hours are among other issues that preclude adolescents from chasing sexual health services [20]. Providing facilities such as sexual health counseling screening for sexual activity are among the factors facilitating adolescent access to reproductive and sexual health services. Providing contraceptives and screening for Sexually Transmitted Diseases (STDs) is necessary to reduce disparities in teen birth rates [21, 22]. Health revolution systems have focused on access to sexual health services by youths and making them more affordable, evidence-based clinical techniques to increase the use and accessibility of services for adolescents. Exploratory studies by health professionals point to the importance of paying attention to adolescents as a specific group, adopting a comprehensive approach, prioritizing health education, and working in the interdisciplinary field. At the same time, barriers such as lack of managerial and financial support, training, and inadequate support have been identified as limiting the implementation and continuity of the YFHSs [23, 24, 25]. Specifically, Hallum-Montes et al. revealed how different factors at the health systems level, such as health center leadership, communication between leadership and staff, staff attitudes and beliefs, use of data for continuous quality improvement, and billing and coding for reproductive health care, work together to influence implementation of new practices in adolescent reproductive health [26].
Providing teenage health services is one of the most important components of life. To be sustained, YFHSs have to be considered part of health policies, programs, and systems and not organized as secluded programs on external support [27]. WHO has recently pointed out the need to move from YFHSs into youth-responsive health systems [28].
Since identifying adolescent health needs, the focus of service delivery has mainly been on access to sexual health care assistance, including HIV issues. Despite the significance of reproductive and sexual health services for adolescents, there is a general agreement that the importance and distribution of illness among adolescents require a much more comprehensive response from the health care system [29]. 
This systematic review aims to assess the perceived barriers and facilitators of adolescent friendly health services in the world. Teens are considered a positive and energetic force for the present and future of a community. They face more complex risks than previous generations but benefit from weaker support. Developing and extending young people’s demands is a concern for all societies. So the results of this study can help us discover barriers and facilitators of adolescent friendly health services. By removing barriers and strengthening facilitators, we will promote the possibility of adolescents accessing adolescent friendly health services. 
An initial search was conducted to determine whether this issue has already been investigated or not. The Joanna Briggs Institute (JBI) database of systematic reviews and implementation reports, the international Prospective Register of Systematic Reviews (PROSPERO), CINAHL, PubMed, and the Cochrane database were searched. However, there were no complete or in-process reviews focusing on perceived barriers and facilitators of adolescent friendly reproductive health services. Our study design is a qualitative systematic review protocol.
Our review has two questions to answer: 
1. What are the perceived barriers to adolescent-friendly health services in healthcare settings?
2. What are the perceived facilitators of adolescent-friendly health services in healthcare settings?
2. Materials and Methods
Registration and methodology
The research protocol was registered in the PROSPERO at the national institute for health research. The registration number in PROSPERO is CRD42019119229. The guidelines of PRISMA-P (Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols) were followed while reporting the study protocol. 
Timeline
After defining search terms, a pilot search was performed, and a data extraction form was developed. A full search was scheduled to start in the first week of February 2019 and extended to the latest, depending on the date of publication of this protocol.
Eligibility criteria
Type of study participants
The review will consider studies that have been conducted on all gender and ethnic groups of adolescents (10-19 years old) that received health services (i.e., the provision of preventive, curative, and rehabilitative services by a trained health worker) as well as their families, and health care providers. Also, we considered studies that focused on Sexual and Reproductive Health (SRH) services for youth. 
Types of intervention(s)/phenomena of interest
The review study will consider qualitative studies which report on the perceived barriers and facilitators of adolescent friendly health services in the world. These perceived barriers and facilitators are defined as beliefs, attitudes, expectations, or understandings from adolescents, families, and health providers. They may also be structural, financial, or organizational barriers or facilitators. 
Context
The interested participants for this review are adolescents, their families, and health providers in various societies and cultures. Those studies in which adolescents receive health care services from an organization all over their education, but obligatory not willingly, will be excluded from pondering.
Type of outcome measures
Primary outcomes:
1. Identifying perceived barriers of adolescent friendly health services in healthcare settings
2. Identifying perceived facilitators of adolescent friendly health services in healthcare settings
Secondary outcomes
1. Identifying barriers (personal, social, political, cultural, economic, etc.) of accessing adolescent friendly health services in the world
2. Identifying facilitators and enhancers for accessing adolescent friendly health services
3. Management of barriers to accessing adolescent friendly health services
4. Providing strategies to improve adolescent friendly health services and adolescents’ access to sexual and reproductive health services
Type of studies 
This review will consider studies from 2000 to 2019 that focus on qualitative data. This research includes but is not limited to study designs, such as phenomenology, grounded theory, ethnography, action research, and feminist research. Text and opinion will not be promised. Qualitative data from mixed methods studies will be included if they had sufficient clear findings to distinguish from the quantitative results. Studies conducted in any country will be involved. There are neither language exclusion criteria nor any other publication restrictions. Studies will be searched from all databases up to now.
Search strategy
The proposed systematic review will be conducted according to the Joanna Briggs Institute (JBI) methodology for systematic reviews of qualitative evidence [30]. The search strategy will aim to find both published and unpublished studies [31]. A three-step investigation strategy will be utilized in this review. Firstly, the search will be carried out in PubMed and CINAHL. Then, according to keywords in the title or abstract of articles, primary articles will be determined. A full search strategy in PubMed is available in Appendix I. Secondly, all keywords are investigated in the mentioned databases. Thirdly, the reference list of all identified reports and articles will be searched for additional studies. Studies from 2000 to 2019 have been considered in this review. Also, there are neither language exclusion criteria nor any other publication restrictions. 
The searched databases include Cochrane Central Register, MEDLINE, Google Scholar, Embase, ProQuest, Scopus, Web of Science, CINAHL, and the Ovid platform. Unpublished relevant studies will be sought after direct contact with authors through searching ProQuest Dissertations and Theses, MEDNAR, Google Scholar, OpenGrey, OAIster, Google, websites of institutions, government agencies, and non-government organizations. These inspections are provided via a list of synonyms using MeSH terms, CINAHL subject headings, and Emtree headings. Introductory keywords for the pursuit will consist of the following terms:
“Adolescent”, “youth”, “teen”, “teenagers”, “young”, “health services”, “friendly”, “health access”, “clinics”, “health delivery”, “health center”, “adolescent health service”, “Reproductive Health Services”, “sexual health service”, “Youth-friendly”, “delivery of health care”, “Facility Access”, “Barrier”, “Personal Barrier”, “Social Norm”, “Social Barrier”, and “Barrier Communication” which will be combined using Boolean OR and AND operators.
The search approach is prepared by an information specialist, and snowballing method will also be used to identify other studies within the references of selected studies.
Data collection and analysis
Selection of studies
Following the search, all identified citations will be collected, uploaded into Endnote X8 (Clarivate Analytics, PA, USA), and duplicates will be eliminated. Then, titles and abstracts are screened by two independent reviewers (MB, FA) for assessment according to the inclusion criteria for the review. Studies containing the above-mentioned inclusion criteria will be spotted accurately, and their full text will be assessed elaborately. Citations and details of eligible full-text studies will be imported into the Joanna Briggs Institute System for the Unified Management, Assessment, and Review of Information (JBI SUMARI) (Joanna Briggs Institute, Adelaide, Australia). Full-text studies that do not meet the inclusion criteria will be excluded by adding reasons in an appendix in the final systematic review report. Included studies will be appraised critically. The study’s conclusions will be notified thoroughly in the final report and depicted in a PRISMA flow diagram. Any discrepancies between the reviewers will be resolved through discussion or using the third reviewer.
Quality appraisal
The quality assessment of all studies will be done using an adaptation of the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) statement [32]. The elements checked in the studies included study demographic characteristics, eligibility, methodology and sampling method, a possible source of bias (particularly selection bias), and missing data. Selected studies will be critically appraised by two independent reviewers using the JBI critical appraisal checklist for qualitative research [30, 31]. Any disagreements between reviewers will be resolved through discussion or with a third reviewer. The critical appraisal results will be reported in a narrative form and in a table. Information from these studies, which will be evaluated, will be extracted and synthesized. The quality of the included studies will be considered in the analysis and will, therefore, be reflected in the findings and conclusion of the systematic review.
Data extraction
Qualitative data will be extracted from papers included in the review using the standardized data extraction tool [31] from JBI SUMARI by two independent reviewers. The extracted data will consist of specific details about the study populations, context, culture, geographical location, study methods, the desired phenomenon (i.e., adolescents, their families, and health providers’ experience of perceived barriers and facilitators expressed as beliefs, attitudes, expectations or understandings), and other information that may be relevant to the review question and specific objectives. Findings and their illustrations will be extracted and assigned the level of validity. Authors of primary studies will send an email for clarification or missing information.
Data synthesis
Qualitative research findings will, where possible, be integrated using JBI SUMARI [31] and the meta-aggregation approach. This process will involve the aggregation or synthesis of results to develop a set of statements that represent the aggregation through assembling the findings and categorizing them based on similarities. Hence, these categories will be subjected to a meta-synthesis to produce a single comprehensive set of synthesized results that can be used as a foundation for evidence-based practice. If we cannot report the findings as categorized, we will write the findings narratively.
Assessing certainty in the findings 
The final synthesized findings will be graded according to the ConQual approach for establishing confidence in the output of qualitative research synthesis and illustrated in the summary of results [33]. The findings include the major elements of the review and details of how the ConQual score is developed. The results will be entered in a table under items such as title, aspired phenomenon, population, and context for the specific review. Each synthesized finding from the study will then be introduced along with the type of research, a score for dependability, credibility, and the overall ConQual score.
3. Conclusion
This systematic review addresses perceived barriers and facilitators of adolescent friendly health services in the world. Developing and extending young people’s demands is a concern for all societies. So the results of this study can help us discover barriers and providers of adolescent friendly health services. By removing barriers and strengthening facilitators, we will promote the possibility of adolescents accessing adolescent friendly health services. 
In this study, we will not critically investigate previous systematic review studies.
Abbreviations
AFHS: Adolescent Friendly Health Services; PROSPERO: International Prospective Register of Systematic Reviews; PRISMA-P: Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols; JBI SUMARI: Joanna Briggs Institute System for the Unified Management, Assessment, and Review of Information; WHO: World Health Organization; STD: Sexually Transmitted Diseases
Study strengths
• We have a registered prospective protocol in PROSPERO.
• We work with the standard guidelines of PRISMA-P. 
• We have no language limitation in the study selection.
• We search a lot of electronic databases, and also we search in Gray literature.

Ethical Considerations
Compliance with ethical guidelines
There were no ethical considerations to be considered in this research.

Funding
This research did not receive any grant from funding agencies in the public, commercial, or non-profit sectors.

Authors' contributions
Conceptualization, Methodology, and Data collection: Mojdeh Banaei and Farzane Alidost; Data analysis and Supervision: Farzane Alidost; Writing – original draft: Mojdeh Banaei and Haniyeh Nazem; Writing – review & editing: Tayebeh Darooneh and Haniyeh Nazem; Statistical analysis: Mojdeh Banaei and Haniyeh Nazem; Funding acquisition and Resources: Tayebeh Darooneh.

Conflicts of interest
The authors declared no conflict of interest.

Acknowledgements
All authors acknowledge Shahid Beheshti University of Medical Sciences to provide the research resources. The authors wish to express their gratitude to the mentioned institute.


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