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PLOS ONE Guidelines for Reviewers

If you have been invited to review a manuscript, please use our online peer review system. This 2 minute video explains how to accept or decline an invitation to review a manuscript.

  1. About PLOS ONE
  2. Criteria for Publication
  3. Overview of the Editorial Process
  4. Reviewer Selection
  5. Using the Reviewer Form
  6. Confidentiality
  7. Timely Review
  8. Anonymity
  9. Editing Reviewers' Reports
  10. Competing Interests
  11. Feedback to Reviewers
  12. Sharing Reviews with Other PLOS Journals

Brief Overview for PLOS ONE Reviewers

  • If you have been invited to review a submission to PLOS ONE then please consult this 2 minute video which explains how to accept or decline the invitation.
  • Then please carefully study our seven Editorial Criteria for Publication as the criteria employed by PLOS ONE are quite different to other journals you may have reviewed for.

1. About PLOS ONE

Scientific progress requires the exchange and discussion of data and ideas. PLOS ONE is a unique publication dedicated to presenting the results of scientific research from any scientific or medical discipline in an open-access environment. At the same time, it provides a forum in which to discuss that research and so provide for each and every paper its maximum possible impact. To achieve this, PLOS ONE combines traditional peer review with 'Web 2.0' tools to facilitate community evaluation and discourse around the published article.

The peer review of each article is rigorous and concentrates on objective and technical concerns to determine whether the research has been sufficiently well conceived, well executed, and well described to justify inclusion in the scientific record. Then, after publication, all articles are opened up for interactive discussions and assessment in which the whole scientific community can be involved.

Unlike many journals which attempt to use the peer review process to determine whether or not an article reaches the level of 'importance' required by a given journal, PLOS ONE uses peer review to determine whether a paper is technically sound and worthy of inclusion in the published scientific record. Once the work is published in PLOS ONE, the broader community is then able to discuss and evaluate the significance of the article (through the number of citations it attracts; the downloads it achieves; the media and blog coverage it receives; and the post-publication Notes, Comments and Ratings that it receives on PLOS ONE etc).

To provide open access, PLOS journals use a business model in which our expenses—including those of peer review, journal production, and online hosting and archiving—are recovered in part by charging a publication fee to the authors or research sponsors for each article they publish. For PLOS ONE the publication fee is US$1350. Authors who are affiliated with one of our Institutional Members are eligible for a discount on this fee.

We also have a fee waiver policy for authors who do not have funds to cover publication fees. Editors and reviewers have no access to payment information, and hence ability to pay will not influence publication decisions. These policies ensure that the fee is never a barrier to publication.

Please see our Frequently Asked Questions (FAQ) page for detailed information on common editorial inquiries.

2. Criteria for Publication

To be accepted for publication in PLOS ONE, research articles must satisfy the following criteria:

  1. The study presents the results of primary scientific research.
  2. Results reported have not been published elsewhere.
  3. Experiments, statistics, and other analyses are performed to a high technical standard and are described in sufficient detail.
  4. Conclusions are presented in an appropriate fashion and are supported by the data.
  5. The article is presented in an intelligible fashion and is written in standard English.
  6. The research meets all applicable standards for the ethics of experimentation and research integrity.
  7. The article adheres to appropriate reporting guidelines and community standards for data availability.

The PLOS ONE board of Academic Editors, and any invited external peer reviewers, will evaluate submissions against these criteria.

To expand on each of these criteria:

1. Does the manuscript report on primary research?

PLOS ONE is designed specifically as a medium for primary, scientific research. As such, it is not suitable for the publication of reviews, mini-reviews, opinion pieces, commentaries, essays or other items of secondary literature (unless invited for a specific purpose by PLOS staff).

Systematic reviews and meta-analyses can be considered for publication in PLOS ONE but must apply the utmost rigour in the comprehensive and unbiased sampling of existing literature and must describe the methods used for the selection, inclusion and exclusion of data (see below).

Individual case reports are not considered for publication in PLOS ONE. However, papers describing the results of studies involving only one individual (ie, n-of-1 studies) can be considered for publication in PLOS ONE if evidence is provided that the paper describes the results of a preplanned research project, rather than a description of the clinical care received by an individual patient.

2. Have the results reported been published elsewhere?

PLOS ONE does not accept for publication work that has already been published elsewhere. However, studies that replicate results that are already in the literature may be considered for publication in PLOS ONE, as the independent confirmation of results can often be valuable, as can the presentation of a new dataset (for example, a new clinical trial).

3. Are the experiments, statistics, and other analyses performed to a high technical standard and are described in sufficient detail?

The research must have been performed to a technical standard high enough to allow robust conclusions to be drawn from the data. Methods and reagents must also be described in sufficient detail so that another researcher is able to reproduce the experiments described.

4. Are the conclusions presented in an appropriate fashion with speculations and hypotheses identified as such?

The results must be interpreted appropriately, such that all conclusions are justified. However, authors may discuss possible explanations for their results as long as these are clearly identified as speculations or hypotheses, rather than as firm conclusions. Inappropriate interpretation of results is a justifiable reason for rejection.

5. Is the article presented in an intelligible fashion and written in English?

PLOS ONE staff do not copyedit the text of accepted manuscripts; it is therefore important for the work, as presented, to be intelligible. Perfect, stylish English is not essential but the language must be clear and unambiguous. If the language of a paper is poor, Academic Editors should recommend that authors seek independent editorial help before submission of a revision. Poor presentation and language is a justifiable reason for rejection.

6. Does the research meet all applicable standards with regard to the ethics of experimentation and research integrity?

Research published in PLOS ONE must have been conducted to the highest ethical standards. A brief description of the most common of these is described in our Editorial and Publishing Policies. Please contact PLOS ONE staff (plosone [at] plos.org) if you have queries as to whether these standards have been met.

7. Does the article adhere to appropriate reporting guidelines and community standards for data availability?

PLOS ONE aims to promote openness in research and intends that all work published in PLOS ONE can be built on by future researchers. We therefore demand conformity to standards for the public deposition of data (for example gene sequences, microarray expression data, and structural studies). Other similar standards that are applicable to specific communities should also be upheld. Failure to comply with community standards is a justifiable reason for rejection. Authors should consult our editorial policies (http://www.plosone.org/static/policies.action#reporting), and the EQUATOR website (http://www.equator-network.org/) for information about the guidelines and standards that apply to their study.

3. Overview of the Editorial Process

PLOS ONE will provide all authors with an efficient and "hassle-free" editorial process. Our aim is to identify those submissions that warrant inclusion in the scientific record and present them to the scientific community with as few hurdles as possible.

The editorial process is run by the journal's extensive board of Academic Editors (AEs) who work together to orchestrate the peer-review process. AEs are invited to handle submitted manuscripts on the basis of the content of the manuscript and their own expertise. The AE evaluates the paper and decides whether it describes a body of work that meets the editorial criteria of PLOS ONE. AEs can employ a variety of methods, alone or in combination, to reach a decision in which they are confident:

  • They can conduct the peer review themselves, based on their own knowledge and experience
  • They can take further advice through discussion with other members of the editorial board
  • They can solicit reports from further referees

After appropriate consideration by the AE, a decision letter to the author is drafted. This letter may also be circulated to other members of the editorial board, who are given a short time to comment on the editorial decision.

There are several types of decisions possible:

  • Accept in principle
  • Minor revision
  • Major revision
  • Reject

Upon acceptance, the manuscript is checked by PLOS ONE staff to ensure that it is in a form that will allow it to be efficiently handled by our production system. The authors will be queried and allowed to make any final minor revisions that are needed.

This is the final stage at which authors will see their manuscript before publication. The authors' files will be carefully tagged to generate XML and PDF files, but will not be subject to detailed copyediting (see Overview of the Production Process). It is therefore essential that authors provide a thoroughly proofread and checked manuscript, following the author checklist and any comments from PLOS staff.

4. Reviewer Selection

Selection of reviewers for a particular manuscript is the responsibility of the AE and is based on many factors, including expertise, reputation, specific recommendations of authors and academic editors, and the AE's own knowledge of a reviewer's past performance.

As part of our editorial procedure, we confer with potential reviewers before sending them manuscripts to review. Reviewers should bear in mind that even these initial messages or conversations contain confidential information, which should be regarded as such.

5. Using the Reviewer Form

PLOS ONE reviewers are asked to complete a structured reviewer form which aims to help reviewers focus on the PLOS ONE publication criteria and improve the efficiency of the peer review process.

Reviewers may preview the full form here.

The form consists of three sections:

  • Statement of Competing Interests (required)

Reviewers must declare any potential or perceived competing interests that may influence their review.

  • Comments to the Author (required)

This section includes questions about whether the submission meets the PLOS ONE publication criteria.

The required questions are:

  1. Is the manuscript technically sound, and do the data support the conclusions?
    • Answer options: Yes, No, Partly
  2. Has the statistical analysis been performed appropriately and rigorously?
    • Answer options: Yes, No, I don’t know, N/A
  3. Does the manuscript adhere to standards in this field for data availability?
    • Answer options: Yes, No
  4. Is the manuscript presented in an intelligible fashion and written in standard English?
    • Answer options: Yes, No

If the reviewer has further feedback about a specific item, it may be included in the optional free-text box following the question.

Reviewers may also raise any additional issues in a free-text response at the end of the form. This question is optional.

The answers to all questions in this section will be included in the decision letter to the author.

There is also a space for reviewers to sign their name if they would like their identity to be revealed to the authors and other reviewers. PLOS ONE encourages transparency in peer review.

  • Confidential Comments to the Editor (optional)

In this section, reviewers may share any comments with the Academic Editor that they do not wish to share with the author. This section is optional, and we strongly encourage reviewers to include all feedback about the scientific content of the manuscript in the "Comments to the Author" section. However, we understand that it may not be appropriate to share some comments with the authors.

This section also includes two optional questions about whether the submission should be highlighted on the PLOS ONE webpage. These questions are part of our effort to develop tools like article-level metrics to highlight specific content. These answers will not play any role in the editorial decision-making process and will not be shared with the authors.

6. Confidentiality

The review process is strictly confidential and should be treated as such by reviewers. As the author may have chosen to exclude some people from this process, no one who is not directly involved with the manuscript (including colleagues and other experts in the field) should be consulted by the reviewer unless such consultations have first been discussed with the Academic Editor. Reviewers must not take any confidential information they have gained in the review process and use it before the paper is published. Even after publication, unless they have the permission of the authors to use other information, reviewers may only use publicly published data (i.e. the contents of the published article) and not information from any earlier drafts.

7. Timely Review

PLOS ONE believes that an efficient editorial process that results in timely publication provides a valuable service both to authors and to the scientific community at large.

8. Anonymity

Although reviewers may remain anonymous during the review process, we strongly urge them to relinquish this anonymity to promote open and transparent decision-making.

9. Editing Reviewers' Reports

The editors and PLOS staff do not edit any comments made by reviewers that have been intended to be read by the authors unless the language is deemed inappropriate for professional communication or the comments contain information considered confidential. Such remarks should be reserved for the confidential section of the review form, which is intended to be read by the editors only. In their comments to authors, reviewers are encouraged to be honest but not offensive in their language. On the other hand, authors should not confuse frank and perhaps even robust language with unfair criticism.

10. Competing Interests

As far as possible, we respect requests by authors to exclude reviewers whom they consider to be unsuitable. We also, as much as possible, try to rule out those reviewers who may have an obvious competing interest, such as those who may have been collaborators on other projects with the authors of this manuscript, those who may be direct competitors, those who may have a known history of antipathy with the author(s), or those who might profit financially from this work. Because it is not possible for all such competing interests to be known by a particular editor, we request that reviewers who recognize a potential competing interest inform the editors or journal staff and recuse themselves if they feel that are unable to offer an impartial review.

Read more about the policy of PLOS regarding competing interests. When submitting your review, you must indicate in the box provided whether or not you have any competing interests. On occasion, reviewers may be asked to offer their opinion on a manuscript that they may have reviewed for some other journal. This is not in itself a competing interest. That two journals have identified the same person as especially well qualified to judge the manuscript under consideration does not in any way decrease the validity of that opinion and may perhaps even enhance it.

11. Feedback to Reviewers

We send reviewers' comments along with the decision letter to reviewers of that manuscript. If reviewers have identified themselves, this information will be passed on to other reviewers. Reviewers who may have offered an opinion not in accordance with the final decision should not feel that their recommendation was not duly considered and their service not properly appreciated. Experts often disagree, and it is the job of the editorial team to make a decision.

12. Sharing Reviews with Other PLOS Journals

PLOS publishes several journals. Occasionally, editors recommend after peer review that a particular article is more suitable for another PLOS journal. If the authors choose to pursue that option, we transfer the manuscript and the reviews to the other journal. We expect that reviewers for any PLOS journal are willing to have their reviews considered by the editors of another PLOS journal.