A systematic review and narrative synthesis will be conducted. This protocol was developed in collaboration with experts in musculoskeletal rehabilitation research and spinal surgery. We used the COnsensus-based Standards for the selection of health Measurement Instruments (COSMIN) methodology and practical tools  for selecting the most suitable outcome measurement instruments. The present review protocol is being reported in accordance with the reporting guidance the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocols (PRISMA-P) statement  (see PRISMA-P checklist in Additional file 1). This review protocol was registered within the International Prospective Register of Systematic Reviews (PROSPERO) (registration number: CRD42020187544). The planned systematic review described in this protocol will be reported following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement .
Our protocol reports two separate stages to allow us to fulfil our objectives. In stage one, studies will be identified that use PROMs to investigate HR-QOL in patients with adult scoliosis. From this search, we will obtain a list of PROMs. In stage two we will then assess the measurement properties of the HR-QOL PROMs identified in stage one.
Stage one: Identifying PROMs of HR-QOL
The stage one search aims to identify all PROMs of HR-QOL in adult scoliosis patients and will be selected based on the following criteria: Participants, Outcome and Study design.
Patients aged 18 years and older with a diagnosis of adult scoliosis, as defined by the SRS with a Cobb angle of more than 10 degrees in the coronal plane .
Our primary outcome is to identify any study that includes a PROM of HR-QOL for patients with adult scoliosis. HR-QOL was defined using the World Health Organization definition, ‘An individual’s perception of their position in life in the context of the culture and value systems in which they live and in relation to their goals, expectations, standards and concerns’ . We have defined PROM according to the Core Outcome Measures in Effectiveness Trials (COMET) taxonomy . Our secondary outcome will be to tally the frequency of use of the PROMs.
All study designs (randomised control trials, cohort studies, observational studies and case studies) will be included with the exception of systematic reviews. There will be no limit on language at this stage.
Stage two: Assessing measurement properties of identified PROMs
The stage two search aims to identify all studies assessing the measurement properties of PROMs of HR-QOL in adult scoliosis patients. Studies will be selected based on the following criteria: Participants, Outcome and Study design.
Patients aged 18 years and older with a diagnosis of adult scoliosis, as defined by the SRS . In cases of mixed cohorts, > 50% of the participants should have adult scoliosis. Authors of studies will be contacted in case of missing information about study participants. Systematic reviews will be excluded as they do not contain original patient information.
The primary outcome will be the measurement properties of PROMs identified in search one. The measurement properties of interest have been selected based on the Delphi study which agreed the measurement properties of interest in HR-QOL PROMs  are:
No planned secondary outcome measures have been identified; however, if during the review process a point of interest is discovered, this information will be collated and reported.
All studies which evaluate one or more measurement properties of the identified PROMs from stage one will be eligible. This includes any development or validation studies of a PROM. Full-text studies not available in English will be excluded.
Information sources and search strategy
A comprehensive search strategy will be performed using National Institute for Health and Care Excellence (NICE) Healthcare Databases Advanced Search (HDAS) tool including the following electronic databases: AMED (from inception onwards) CINAHL (from inception onwards), EMBASE (from inception onwards), Medline (from inception onwards), PsychINFO (from inception onwards) and PubMed (from inception onwards)) following consultations with experts and based on scoping searches. Additional specific searches of specialist spinal journals will also be performed. Study authors will be contacted if clarification is required.
An example of the stage one search strategy is included as additional file 1. Multiple uses of the same outcome measure will be tallied.
Searches will be performed using NICE HDAS tool by two authors (JA and CB). The results will be exported into the Rayyan QCRI  tool to allow for removal of duplications. This tool then allows for simultaneous blinded review of the potentially eligible studies by the two reviewers (JA and CB) before unblinding and comparison of decisions. This method will be used for both search one and search two. After the initial screening of the title and abstract, full articles will then be exported to Mendeley (London, UK) and reviewed individually.
A standardised selection process will be performed by two independent authors (JA and CB). In stage one and two, the titles and abstracts will be assessed against the pre-determined selection criteria. Any article where the title and abstract do not provide a clear answer, the full-text article will be retrieved and reviewed. A PRISMA diagram will be constructed  to allow transparency over the study flow including reasons for exclusion of studies. Articles will be included if both reviewers agree. In any case of disagreement, this will firstly be discussed between the two authors and any remaining disagreement will then involve the senior author (AG) who will mediate and make a final decision if required.
Data collection process
Once studies have been identified, two authors (JA and CB) will extract the data from the studies independently and in duplicate. Data will be collected into an ‘overview table’ as suggested by the COSMIN methodology . This table is available as additional file 3. If additional information is required, corresponding authors will be contacted by email.
The data will be collected into an overview table, which is available as additional file 3.
The data which we will be collecting relate to the participants, outcome and study design. We will collect data on the participants age, gender and scoliosis subtype to allow for assessment of variation between these characteristics.
Data on the PROMs will be collected to allow comparison of the various PROMs and their characteristics. We will also collect data on the measurement properties of these PROMs from within the studies.
Information on the study design will be collected to allow identification of the important characteristics of the studies which will contribute to our final synthesis of the available evidence.
We will not collect any data on funding sources or additional items. We have not made any pre-planned data assumptions or simplifications.
Risk of bias in individual studies
Single studies may assess multiple measurement properties and therefore these will be considered separately. For each of the measurement properties, a four point rating of Very good, Adequate, Doubtful or Inadequate will be awarded. The rating will be based on the COSMIN checklist and will be performed independently by two authors (JA and CB) at the level of the study. The two authors will then discuss the outcome and any disagreements will be settled by a senior third author (AG). The agreement between assessors will be reported as a percentage. The overall rating for any given study will be based on its lowest scoring standard . This information will help to inform the synthesis as studies with a doubtful or inadequate rating will impact on the overall assessment of the quality of the evidence.
Narrative synthesis aims to explore heterogeneity within primary studies in a descriptive manner rather than statistically. Narrative synthesis can be broken down into four elements :
Developing a theory of how the intervention works, why and for whom
Developing a preliminary synthesis of findings of included studies
Exploring relationships in the data
Assessing the robustness of the synthesis
Guidance exists to support the PRISMA statement in those circumstances when meta-analysis is not possible . This methodology will be followed for reporting the narrative synthesis.
If studies demonstrate sufficient methodological and clinical similarities, the results will be pooled by measurement property and by PROM. Quantitative pooling will only be performed from data regarding patients with adult scoliosis collected using the same statistical parameters. From scoping searches, the authors anticipate that the data will not be suitable for quantitative pooling as the statistical parameters are not consistent. Therefore, a narrative synthesis of the results will be necessary. There is no plan to assess for meta-bias within this review.
Confidence in cumulative evidence
The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach using five factors (Risk of bias, inconsistency, indirectness, imprecision and publication bias) will be used to assess the quality of the evidence and produce a rating of ‘High’, ‘Moderate’, ‘Low’ or ‘Very low’ [33, 34]. As described by the COSMIN methodology, publication bias will not be assessed. In the case of inconsistency, and where results cannot be pooled or summarised, the conclusion will be based upon the consistent results which make up the majority. However, the quality of evidence will be downgraded for inconsistency.
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