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Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

Reviewer #1: Yes

Reviewer #2: Partly

Reviewer #3: Yes

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2. Has the statistical analysis been performed appropriately and rigorously? -->?>

Reviewer #1: N/A

Reviewer #2: Yes

Reviewer #3: Yes

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3. Have the authors made all data underlying the findings in their manuscript fully available??>

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.-->

Reviewer #1: No

Reviewer #2: Yes

Reviewer #3: Yes

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4. Is the manuscript presented in an intelligible fashion and written in standard English??>

Reviewer #1: Yes

Reviewer #2: No

Reviewer #3: Yes

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Reviewer #1: Reviewer Report

General Assessment and Recommendation

This manuscript addresses an important gap in the evaluation of compensatory movement patterns in individuals with brachial plexus injury (BPI) during one-handed functional capacity evaluation (FCE-OH). The authors propose and test a novel observational scoring system for identifying compensations, and report inter- and intra-rater reliability based on video assessments by 16 raters. The study is original, methodologically sound in many respects, and clinically relevant. However, several methodological, statistical, and reporting issues need clarification and strengthening. I therefore recommend Major Revision.

1. Scope and Novelty

The manuscript is well-positioned: FCE-OH is widely used for work capacity evaluations, yet does not capture how tasks are performed. The observational scoring system adds a qualitative layer that can be highly valuable in preventing musculoskeletal complications due to compensatory movements.

Prior tools developed for prosthesis users are not directly transferable, which justifies the development of a new scale specifically for BPI.

The work is timely and relevant to rehabilitation, occupational health, and clinical ergonomics.

Strengths: International pool of raters, two test sessions to assess stability, item-level analysis, and the addition of an applicability survey.

2. Study Design and Scale Development

Major Revision Request 2.1 – Content validity:

The development process is described but lacks systematic reporting of item generation and expert consensus. How were “within normal limits (WNL)” versus “not WNL” decisions operationalized? The current items are largely symmetry-based; clearer operational definitions and anchor examples (possibly visual diagrams) should be provided in the supplementary material.

Major Revision Request 2.2 – Stratification:

Given the heterogeneity of BPI, stratification by residual function (e.g., ROM, strength categories, lesion levels) is warranted to illustrate item performance across subgroups. This would help clarify whether some items are only reliable in particular clinical subpopulations.

Major Revision Request 2.3 – Training protocol:

Over half of the raters felt that the video-based training was insufficient. A structured training module (e.g., a set of “gold standard” clips with feedback and short quiz) should be outlined, and the improvement from session 1 to session 2 should be explicitly analyzed as a “learning effect.”

3. Statistical Analysis and Reliability

Major Revision Request 3.1 – Kappa limitations:

Low kappa values despite moderate absolute agreement suggest prevalence/bias effects. The authors should include prevalence and bias indices, and/or alternative coefficients such as Gwet’s AC1/AC2 or PABAK.

Major Revision Request 3.2 – Advanced modeling:

If feasible, consider multi-level approaches (e.g., Generalizability Theory or mixed-effects logistic regression), which can simultaneously model variance due to rater, video, and session factors.

Major Revision Request 3.3 – Item-level behavior:

The weakest performance was for overhead lifting items. These may conflate several compensations (shoulder, trunk, elbow). Splitting them into subcomponents could improve clarity and rater agreement.

Revision Request 3.4 – Power and CI width:

Confidence intervals are relatively wide. While the exploratory nature is acknowledged, a brief power calculation or justification of sample size relative to target kappa would add transparency.

4. Video Protocol and Practical Implementation

Several raters reported difficulty due to loss of the sagittal plane in some videos. For future work, multi-angle recordings (front, side, posterior) or camera tracking should be considered.

The instruction that raters could not pause or replay videos mirrors real clinical practice, but should be explicitly justified and included in the user manual.

5. Interpretation of Results

The improvement from session 1 to session 2 suggests a training effect. Quantifying this difference statistically (e.g., confidence intervals for session-to-session change in kappa) would strengthen the claim.

The interpretation of “almost sufficient” reliability should be replaced with numeric ranges and standard thresholds for clarity.

The finding that intra-rater reliability is sufficient while inter-rater reliability is moderate should be highlighted as both a limitation and an opportunity for further rater training.

6. Data Availability and Ethics

Ethics approval and informed consent are clearly stated.

Data availability statement is appropriate. However, I recommend sharing the raw rating matrix, anonymized survey results, rater instructions, and—if ethically permissible—short example video clips in an open repository with DOI. This will greatly facilitate replication and training.

7. Writing, Language, and Presentation

Minor typographical errors should be corrected (e.g., “abled bodied” → “able-bodied,” “prothesis” → “prosthesis”).

Abbreviations should be defined upon first use (e.g., FCE-OH, WNL).

Tables and figures should be polished: abbreviations expanded, statistical measures (κ, CI, % agreement, prevalence) clearly presented.

Supplementary materials should include the final scoring system in a single consolidated PDF.

Reviewer #2: 1. Claims & Framing

• Abstract results, discussion and conclusions overstate κ values as “sufficient,” whereas they are best described as moderate (κ≈0.59–0.64).

• The novelty of the tool compared with prior prosthesis-user and observational/postural tools is not sharply positioned in discussion and introduction.

2. Scale Development (Methods)

• The reliance on one student, one professional, and internal group consensus limits the robustness of the item selection; broader expert involvement (e.g., multiple clinicians or a Delphi panel) would improve validity.

• The choice of a >2 SD threshold is statistical but not clearly justified clinically. Why is this cutoff appropriate for defining abnormal compensation?

• The binary WNL/nWNL scoring system is simple and practical, but may oversimplify nuanced compensatory behaviors. A graded scale (e.g., mild/moderate/severe deviation) could capture variation more effectively.

3. Raters, Training, and Blinding (Methods)

• The manuscript does not describe how raters were trained, calibrated, or whether their backgrounds (clinical vs non-clinical) might have influenced ratings. This is a crucial omission, as interrater reliability depends heavily on training consistency.

• It is unclear whether raters were blinded to diagnosis (BPI vs control). Knowledge of group assignment could bias assessments.

• The questionnaire is only briefly mentioned. No details are provided regarding its design, validation, or analysis. Without transparency, these findings cannot be meaningfully interpreted.

4. Sample Size & Power (Methods)

• The sample size (15 BPI, 21 controls, 16 raters) is modest. No power calculation or justification is provided. Reliability studies require such justification to ensure κ estimates are stable.

5. Statistics & Interpretation

• The Results section is statistically adequate but lacks depth: (1. Were reliability values consistent across different FCE tasks, or did some tasks show higher agreement? 2. Were there systematic differences in rating patterns between raters with different professional backgrounds? 3. Were there differences in reliability between the BPI and control groups?)

• The discussion should address why interrater reliability improved from session 1 to session 2. Was this due to learning effects, improved familiarity with the tool, or random variation? Without exploring this, the findings are difficult to contextualize.

• Although most raters described the tool as “easy to use,” only ~50% considered it clinically feasible, citing insufficient training. This contradiction requires deeper analysis.

6. Language & Structure

• Minor grammar/typography:

The keywords in the PLOS ONE submission system contain a typo and should be carefully checked.

Line 238: “video’s” should be corrected to “videos.”

Consistently use prosthesis (not prothesis).

Perform a thorough proofread to correct similar small grammar, pluralization, and capitalization issues throughout the text.

• Limitations section:

The Limitations are presented in great detail, but the section currently reads as overly long, repetitive, and weighted with procedural details. While transparency is commendable, the narrative would benefit from focusing on the most impactful issues and reframing them in a forward-looking way.

Reviewer #3: ⦁ Can you expand more on the background part on the abstract

⦁ In the introduction part, "Individuals with brachial plexus injury (BPI) need to compensate for the loss of function of theaffected arm." I suggest first to give a brief mechanism of action and intervention of the brachial plexus anatomy and physiology

⦁ Can you mention if the able bodied controls aware of the research and that they are being controls or if it was blinded to them?

⦁ In the mentioned raters part "Twenty raters were recruited using an international Linked-In FCE research network and by contacting medical professionals at our local medical center" can you mention more about the expertise of the raters whether they are MDs or experts in Orthopedics or Physical Therapy.

⦁ From this part "Recruitment of the raters took place from 19 November 2021 to 1 February 2022" can you mention also the time frame of observing movement patterns

⦁ in Line 148 "Video recordings of 15 individuals with BPI performing FCE-OH tests (2 females, 13 males, mean age 49.9 ± 10.9 years, mean time since onset BPI 9.6 ± 9.7 years, recorded during a previous study that aimed to determine the functional capacity of individuals with BPI" i suggest and encourage the authors to provide a table for better visualization and show data

⦁ Also in Line 153-154 "four had a full active range of motion of the affected limb and eleven had a diminished active range of motion of at least one joint caused by contractures or limited strength. also a table here will lead to a better visualization

⦁ Same Applies to line 169

⦁ Please reorganize wording and clarity in here "Only three out of eight items of the rating system for upper limb prosthesis wearers were suitable for use in individuals with BPI (overhead lifting test two211 handed; items trunk and shoulder movements and fingertip dexterity test; item trunk movements)" as which were the 3 items used

⦁ in Line 223 " Some video recordings appeared to be more difficult to rate than others. In order to reduce the influence of one single video recording on the results, eight video fragments were rated in pilot test 3, 4 and 5. Raters of these pilot tests were also asked to rate the certainty of their ratings (dichotomous, certain: yes or no), in order to identify difficulties in rating." Were single Videos was evaluated by one rater only? if yes can you mention that in the limitations section as operator bias might present

⦁ In Line 318, Feasibility and usability I would also encourage having a diagram, table, or chart presenting the data

⦁ Great Use of the matrix of discussion. a one point to add is just comparing current study findings to the two studies that evaluated the use of compensatory movements you mentioned before

⦁ I suggest restructuring the discussion and limitation parts as limitation part have an enormous amount of paragraphs suitable in the discussion

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Reviewer #1: No

Reviewer #2: Yes:Dr.Fawwaz Al-SmadiDr.Fawwaz Al-SmadiDr.Fawwaz Al-SmadiDr.Fawwaz Al-Smadi

Reviewer #3: Yes:Nasser F. AlSunbulNasser F. AlSunbulNasser F. AlSunbulNasser F. AlSunbul

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Submitted filename: Reviewer Report_plos.docx

Development and reliability testing of a qualitative observational rating system for individuals with brachial plexus injury performing Functional Capacity Evaluation tests.

PONE-D-25-38741R1

Dear Dr. Tallie van der Laan,

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Kind regards,

Priti Chaudhary, M.S.

Academic Editor

PLOS One

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