-->PONE-D-25-42511-->-->The modified 30-second chair stand test (m-30s-CST) is more sensitive than handgrip strength in detecting muscle strength changes and predicting physical performance and mortality in hospitalized geriatric patients-->-->PLOS ONE

Dear Dr. Sipers,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

The limited sample size, potential selection bias, lack of adjustment for key confounders, and the empirical definition of m-30s-CST cut-offs weaken the strength of the conclusions. A major revision is required to improve the statistical robustness, clarify the definition of functional outcomes, and better highlight the clinical implications for geriatric practice.

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Additional Editor Comments:

The study addresses an important and clinically relevant question in geriatric hospital care and is clearly written. However, several methodological and analytical issues need to be addressed before the manuscript can be considered for publication. In particular, the limited sample size, potential selection bias, lack of adjustment for key confounders, and the empirical definition of m-30s-CST cut-offs weaken the strength of the conclusions. A major revision is required to improve the statistical robustness, clarify the definition of functional outcomes, and better highlight the clinical implications for geriatric practice.

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Reviewers' comments:

Reviewer's Responses to Questions

-->Comments to the Author

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

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented. -->

Reviewer #1: Yes

Reviewer #2: Yes

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

Reviewer #1: Yes

Reviewer #2: 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.-->

Reviewer #1: Yes

Reviewer #2: Yes

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Reviewer #1: Yes

Reviewer #2: Yes

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-->5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)-->

Reviewer #1: The authors compare the modified-30s-Chair-Stand-Test (m-30s-CST) with handgrip strength (HGS) in measuring muscle strength in acutely ill geriatric patients. Responsiveness of the m-30s-CST and HGS was assessed in 92 patients (mean age 84±6 y, 53.5% female) by comparing the performance at hospital admission and the day before discharge. These changes were then compared with changes in the ADL-Barthel-Index (ADL-BI) and Short Physical Performance Battery (SPPB). The number of repetitions on the m-30s-CST increased significantly during hospitalization in patients who improved on ADL-BI (n=43) and SPPB (n= 33) and did not change in those who remained stable or worsened (ADL-BI: n= 32 and SPPB: n= 26). There was no significant change in HGS in either patients who improved on respectively ADL-BI (n=43) and SPPB (n=41), nor in those who remained stable or worsened (ADL-BI: n=31 and SPPB: n= 34). Two-year mortality was significantly higher in geriatric patients with low performance on the m-30s-CST. HGS was not associated with 2-year mortality.

The manuscript is interesting but I have some concern about the clinical status of the patients.

1) Frailty: you are considered only physical frailty and not multidimensional frailty. Please see and discuss: Liguori I et al. Validation of "(fr)AGILE": a quick tool to identify multidimensional frailty in the elderly. BMC Geriatr. 2020 Sep 29;20(1):375.

2) Catabolic syndrome: what about parameters characterizing the “catabolic syndrome” in these patients? Please see and discuss: Curcio F et al. The reverse metabolic syndrome in the elderly: Is it a "catabolic" syndrome? Aging Clin Exp Res. 2018 Jun;30(6):547-554.

Reviewer #2: The study addresses a clinically relevant question in hospital geriatrics: which strength test better reflects changes in physical performance and predicts mortality in acutely ill older adults. The modified 30-second chair stand test (m-30s-CST) was compared with handgrip strength (HGS) in 92 patients (mean age 84 years). The authors found that the m-30s-CST was more responsive to in-hospital changes and a stronger predictor of two-year mortality, while HGS showed no significant associations.

This is a well-written and interesting paper. It provides practical insight into functional assessment in frail geriatric patients and highlights the limitations of handgrip testing in this setting.

Some methodological limitations, however, should be considered:

• The sample size is relatively small and derived from a single center, which limits generalizability.

• A large number of exclusions may have introduced selection bias. This also underlines a limitation in the applicability of the m-30s-CST in the acute hospital setting.

• It is not entirely clear which level of ADL function is considered at admission — the one assessed at the time of hospitalization (which may already be unrealistic and influenced by multiple confounding factors) or the premorbid status immediately before the acute event. In any case, the definition of "incident disability" (new-onset disability) related to hospitalization remains conceptually problematic for the study’s interpretation.

• The Cox analysis included only a few covariates and did not adjust for potential confounders such as length of stay, immobilization, or rehabilitation interventions.

• No measure of muscle mass was included, preventing an integrated analysis of structural sarcopenia.

• Mortality cut-offs for the m-30s-CST were defined empirically rather than validated. Given this, I recommend performing a ROC curve analysis to identify the optimal cut-off value and quantify the test’s discriminative power (AUC). This would strengthen the statistical validity of the conclusions and allow direct comparison with handgrip strength.

• Functional outcomes beyond mortality (e.g., falls, readmissions, recovery of autonomy) were not assessed, although these would be clinically meaningful in this population.

• Finally, the discussion and conclusions could more clearly highlight the key clinical message and what this study adds to daily geriatric practice.

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Reviewer #1: No

Reviewer #2: No

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The modified 30-second chair stand test (m-30s-CST) is more sensitive than handgrip strength in detecting muscle strength changes and predicting physical performance in hospitalized geriatric patients

PONE-D-25-42511R1

Dear Dr. Walther Sipers ,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

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Kind regards,

Francesco Curcio, M.D., Ph.D.

Academic Editor

PLOS One

Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

-->Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.-->

Reviewer #1: All comments have been addressed

Reviewer #2: All comments have been addressed

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-->2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented. -->

Reviewer #1: Yes

Reviewer #2: Yes

**********

-->3. Has the statistical analysis been performed appropriately and rigorously? -->

Reviewer #1: Yes

Reviewer #2: Yes

**********

-->4. 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.-->

Reviewer #1: Yes

Reviewer #2: Yes

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-->5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.-->

Reviewer #1: Yes

Reviewer #2: Yes

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-->6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)-->

Reviewer #1: The manuscript is really improved. All questions have been arised. The manuscript merits to be published.

Reviewer #2: The manuscript is improved and points of criticism were analysed and discussed in the limitation of the study section. I found the manuscript suitable for publication.

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-->7. PLOS authors have the option to publish the peer review history of their article (what does this mean? ). If published, this will include your full peer review and any attached files.

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Reviewer #1: No

Reviewer #2: No

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