PONE-D-23-31816Left-digit bias in out-hospital cardiac arrest : The JCS-ReSS studyPLOS ONE

Dear Dr. Mizuno,

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.

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3. One of the noted authors is a group or consortium "the Japanese Circulation Society Resuscitation Science Study (JCS-ReSS) Group". In addition to naming the author group, please list the individual authors and affiliations within this group in the acknowledgments section of your manuscript. Please also indicate clearly a lead author for this group along with a contact email address.

Additional Editor Comments:

This is a structured approach to assess cognitive bias (left digit bias) among caregivers who performed cardiopulmonary resuscitation on patients outside the hospital.

I would like to see a slightly more expanded introduction, with greater exposition of the rationale that led to the development of the tested hypothesis.

I would like to see a more structured methodological process. I understand that this sample comes from a large study, however I believe that it would be more useful in understanding the results to have a broader view of the population base and its characteristics.

I believe it would be useful to present the results of the models developed in tables. Reading the graph is limited only to the dynamics of the phenomenon.

In Table 1 there is a statistical procedure applied, however it is not possible to understand the statistical origin of the p values by reading the methods.

The implications of this study's findings are unclear to me, even after some reading.

Furthermore, I would like to draw special attention to two points that are very strong in the reviewers' assessment.

1) It would be valuable to conduct a sensitivity analysis in which the authors compare the adjusted likelihood of resuscitation for patients age 79 vs 80 (as well as 78 vs 79 and 80 vs 81). Given that this is a negative study, confirming the null finding with such an alternative analytic approach would strengthen the veracity of the study.

2) According to the authors, a case where the age factor could potentially play out a role in decision making was defined to be a case witnessed by family members (but the life-support assistance could be provided by family members, paramedics, or physicians). However, the authors did not provide adequate information for whether the relevant protocol did instruct (or lead to a high likelihood) that the patient’s age be made known (in this case) to non-family members like paramedics and physicians *before* such an emergency medical intervention decision (and whether the relevant protocol would even instruct that age be considered as an agent for decision making in this case). Thus, whether the current case-selection criterion is a valid definition remains unclear and needs to be addressed by the authors.

In addition, to the important contribution made by the reviewers, I believe that the points mentioned above and copied by me here are relevant for a final opinion. I hope that the authors can create a new version considering all the points addressed by the referees and this academic editor. I will be proud to review this important material again.

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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: No

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

Reviewer #1: Yes

Reviewer #2: No

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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: No

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4. 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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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: In this retrospective study using Japanese registry data, the authors investigate whether there is evidence of a left-digit bias in patient age on the performance of bystander CPR and pre-hospital ACLS. Analyzing over 384,000 witnessed cardiac arrests, they found that there was no left-digit effect at thresholds of 60, 70, 80, or 90 years of age. The analytic approach is valid and the conclusions are balanced and appropriate. Overall, I agree that there is value to publishing a “negative” study in this space that helps elucidate the types of scenarios in which cognitive biases like left-digit bias are unlikely to play a role.

I have 2 minor comments and one potential sensitivity analysis that I would suggest addressing in the discussion:

-First, as show in Fig 1, the author found that there is no association between age and bystander CPR at all. The lack of discontinuities therefore must be better reconciled with this finding, in that the absence of a left-digit bias for this finding may also be due to the fact that age is not a salient variable in this decision making. To give an extreme/absurd corollary: we would never expect there to be a left-digit bias between fingernail length and bystander CPR because clearly no bystander would even consider fingernail length as a salient characteristic when determining whether CPR should be performed.

-Second, I think there needs to be much greater discussion about the fact that another plausible mechanism is that exact age may not be known to the bystander, thereby making it impossible for a left digit effect to play a role. This is mentioned in the limitations but should be expanded in the main portion of the discussion that covers potential mechanisms.

-It would be valuable to conduct a sensitivity analysis in which the authors compare the adjusted likelihood of resuscitation for patients age 79 vs 80 (as well as 78 vs 79 and 80 vs 81). Given that this is a negative study, confirming the null finding with such an alternative analytic approach would strengthen the veracity of the study.

Reviewer #2: This study investigated whether the left-digit bias (LDB) would affect resuscitation decisions made on individuals OHCA cases where ages of the patients might be a known parameter. Specifically, OHCA cases witnessed by family members from 2005 to 2020 in a case registry database were obtained and a nonparametric regression discontinuity design was used to assess whether “cut-off” values for age thresholds (i.e., 60, 70, 80, and 90) explained drops in the frequency of life-support actions taken on these OHCA cases by family members, paramedics, and physicians. Among all the outcome areas assessed, the authors reported to identify no discontinuity. Although this study has a few merits (e.g., being the first to investigate the effect of LDB in life-support decisions on OHCA cases), I would like to recommend that the authors make a major revision where a few matters be reconsidered as listed below:

The most important question I have for the authors has to do with their analytical method choice and approach, given the underlying concept for LDB. What really detects whether there is an influence by LDB here in this context is that numeral pairs with identical (or almost indistinguishable) magnitude differences but different leftmost digit pairs (e.g., a 69-vs.-70 age numeral pair vs. a 68-69 or 70-71 age numeral pair) are treated significantly different in the outcome domains (e.g., in the context of the present study, it would be a *more* significant drop between a 69-vs.-70 pair than the difference (if any) observed in the other two pairs). The current analytical approaches, by just trying to detect whether there is a discontinuity at cut-off values like 60, 70, etc., could not adequately address the central question regarding an LDB effect. I would suggest that the authors consider a different statistical method that compares the differences in the outcomes among these age value-pairs with the same magnitude differences but different leftmost digit pairs.

In addition, statistical significance was not reported. I would also invite the authors to double check the accuracy for all the reported coefficient values (e.g., on the last line on p.8 for one of the coefficients for family members’ performance of mouth-to-mouth ventilation: it was reported to be -0.002, while the 95% CI was bounded by two positive values).

A second question I have is whether the current domain area (i.e., emergency decisions of life support for individuals with cardiac arrests) is a theoretically motivated or meaningful one to test the effect of LDB on medical decisions. Given the nature of this kind of medical situations (and as the authors have also tackled), age-related factors may not even be taken into consideration. Thus, the hypothesis for why LDB as a cognitive bias could even potentially (or theoretically) influence the relevant decision outcomes in this domain area does not seem to be well grounded (or at least, this was addressed in the Introduction). Therefore, it is not clear why the authors chose this particular domain area for investigating the LDB effect. I would invite the authors to provide more information in the Introduction section to address this matter.

My last major question is about the case-selection criteria. According to the authors, a case where the age factor could potentially play out a role in decision making was defined to be a case witnessed by family members (but the life-support assistance could be provided by family members, paramedics, or physicians). However, the authors did not provide adequate information for whether the relevant protocol did instruct (or lead to a high likelihood) that the patient’s age be made known (in this case) to non-family members like paramedics and physicians *before* such an emergency medical intervention decision (and whether the relevant protocol would even instruct that age be considered as an agent for decision making in this case). Thus, whether the current case-selection criterion is a valid definition remains unclear and needs to be addressed by the authors.

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Reviewer #1: No

Reviewer #2: No

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Left-digit bias in out-hospital cardiac arrest : The JCS-ReSS study

PONE-D-23-31816R1

Dear Dr. Mizuno,

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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Chiara Lazzeri

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: No

Reviewer #2: No

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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

**********

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 authors have adequately addressed my concerns. This manuscript has limitations related to its observational nature, but the discussion covers these

Reviewer #2: The revised manuscript and the author's response have addressed all the questions I have previously raised.

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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.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: No

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