Using an expert survey and user feedback to construct PRECHECK: A checklist to evaluate preprints on COVID-19 and beyond

Ethical considerations

The entire project “PRECHECK: A checklist to evaluate COVID-19 preprints” was conducted under the ethical policies of the University of Zurich. As stipulated in sections 5 and 6 of these policies (https://www.rud.uzh.ch/dam/jcr:c42f07d3-2e89-485c-8a8b-3a3c3f46a3f5/UZH%20Policy%20on%20the%20Ethical%20Review%20of%20Research%20Projects%20Involving%20Human%20Subjects%20 (UZH%20Ethics%20Policy).pdf), our project falls outside the scope of the Swiss Human Research Act and, per section 8.1 of these policies, can be considered as a study that “generally cannot harmfully affect study participants”. Therefore, our project did not require explicit prior ethical approval from the institution, and for this reason we did not ask for ethical approval from the institution. A post-hoc verification with the University of Zurich ethical commission’s ethics review checklist (available in in the OSF repository for this project⁵⁴) confirmed that we did not require ethical approval from the current project per the regulations of the University of Zurich. Written consent for participating in student workshops was not required because the workshops were administered as part of their regular university courses (details in manuscript) to which students do not need to exceptionally consent. Moreover, no data was collected from students, nor was it incorporated in the PRECHECK checklist. There was no relationship of dependence between the students and the workshop presenters (i.e., they were not involved in the grading of the students’ course assignments or exams). In the workshops for journalists, some participants offered unsolicited feedback; these participants were aware that their feedback would be used for this purpose through the presentation given during the workshop.

Study design

The aim of the study was to develop simple and clear guidance, in the form of a checklist, to help assess the quality of a preprint. Our target audience for the checklist were scientifically literate non-specialists, such as students of medicine and psychology, and science journalists. These two target groups were selected, first, for convenience since we had direct access to them. Second, as detailed in the introduction, the COVID-19 pandemic and its flood of research was the primary motivation for the development of the checklist and science journalists were the logical target group to address. Third, our student populations had also been exposed to preprints more intensively during the COVID-19 pandemic and we targeted them in our educational mandate. To develop a checklist that would be both user-appropriate, and discriminative of preprints of different levels of quality, we applied a multi-step approach inspired by the qualitative Delphi method.^55,56 As such, our study could be considered a qualitative study, and we have thus followed the Standards for Reporting Qualitative Research (SRQR) (Ref. 57; see Ref. 54 for a completed version of the checklist for the current project). The Delphi method uses successive voting by expert groups to iteratively narrow down a pool of options until consensus is reached and is effective in determining consensus in situations with little to no objective evidence.⁵⁸ Our procedure involved four main stages. The first draft of the checklist was developed by the junior members of the team after an initial review of the literature and potential solutions (which forms the introduction of this paper). In the first stage, this draft was reviewed internally by the senior members of our team (who were not involved in creating the draft) and subjected to pilot testing to verify whether the checklist could discriminate high- from low-quality preprints [2] if used by experts. In the second stage, a panel of external experts rated the relevance of each element of the checklist and provided feedback, after which the checklist was updated. In the third stage, we conducted a final round of internal review producing the third draft of the checklist, which was also submitted to a final pilot testing. At the end of the above three stages, we verified if members of our target audience could use the checklist successfully and if they appeared to find it useful, via workshops with university students and journalists. We called this stage the Preliminary implementation of the checklist. In the workshop for journalists, some participants offered unsolicited yet helpful feedback, which was incorporated into the finalised version of the checklist (see also Figure 2). These participants were aware that their feedback would be used for this purpose through the presentation given during the workshop. We caution that the chosen setup of the Preliminary implementation stage does not allow a systematic validation of the checklist, especially since the target group was chosen mainly for convenience.

Figure 2. The stages of our Delphi-inspired approach to creating the PRECHECK checklist.

There are four successive stages (Stage 1 – Stage 3 and the implementation stage, in blue, green, yellow, and purple fields, respectively) where each is made up of a set of successive steps (in white rectangular fields).

Researcher characteristics

The research team conducting the analysis was composed of three junior researchers (postdoctoral level) and three senior researchers (two professors and one senior scientific collaborator). All members of the team have experience in meta-research, but are trained in other disciplines (statistics and psychology).

Internal review

In this step, the three senior members of our team gave written feedback on a draft of the checklist in the form of comments. After the written feedback was incorporated by two junior members of our team, final feedback in the form of verbal comments from the senior members was obtained in an online meeting round. A copy of each version of the checklist after feedback and other validation procedures below is available in the OSF repository for this project.⁵⁴

Pilot testing

After each of the two rounds of internal review (Stage 1 and Stage 3), we conducted pilot testing in order to verify whether the checklist, at its given stage of development, could successfully discriminate between preprints of different levels of quality. We did not perform any statistical analyses as part of this assessment. Since objective criteria for quality that would apply to all preprints across disciplines were difficult to envision, we used a list of milestone research works in the COVID-19 pandemic⁵⁹ as a proxy of high quality, and we identified what would be the preprints in our high-quality set from this list. The preprints that would make up our low-quality set, on the other hand, were chosen from a list of retracted COVID-19 preprints,⁶⁰ with retraction being a proxy for low quality. There were no a-priori criteria for selecting preprints. We selected three high-quality preprints^61–63 and three low-quality preprints^11,64,65 to test across multiple stages. Since preprint selection occurred in August 2021, we only included preprints that were available online from the start of the pandemic up until that point. In the Stage 1 round, one junior team member tested only the high-quality preprints and another junior team member the low-quality preprints. In the Stage 3 round, both team members tested all preprints independently. The same high- and low-quality preprints were used at both stages. To document the test results, a spreadsheet was generated with one field per checklist element, where the response to the checklist element for each preprint was entered. Fields were also coloured red, green, and yellow, to visually better represent ‘yes’, ‘no’, and ‘maybe’ responses to specific checklist elements, respectively. The results of each round of pilot testing with the links to the respective preprints are available in the Open Science Framework (OSF) repository for this project.⁵⁴ Due to the limited number of assessed preprints, only a qualitative summary of the results is possible and no statistical analysis of these results is provided.

External expert review

Panel selection

We invited a total of 54 experts across four topic groups: research methodology (14 invitations), preprints (15 invitations), journal publishing (15 invitations), and science journalists (10 invitations), as these fields of expertise were judged to be of the greatest relevance for evaluating our checklist. Experts were identified through personal connections, by identifying editors of relevant journals in the fields of psychology and medicine (for the editor cohort), science journalists from a list of speakers at the World Conference of Science Journalists, Lausanne 2019 (https://www.wcsj2019.eu/speakers); for the science journalism group), and identifying individuals whose work in the topic areas of research methodology and preprints is noteworthy and well-known. Thus, we invited science journalists, journal editors, as well as researchers whose research focuses on research methodology and preprints. There were no a-priori criteria for selecting experts, other than their perceived belonging to one of the topic groups. In actual Delphi designs, 5-10 experts may be considered sufficient,⁶⁶ however, there is no clear consensus on how large expert groups should be.⁶⁷ Of the total number of experts, 29 were personal contacts. Panel members were contacted by email between October 18 2021 and November 16 2021 with a standardised explanation of the project, their role in the refinement of the checklist, how their data would be used (that their name and email will not be shared, that their responses will be fully anonymous, and that the aggregated results will be published and shared on our OSF repository for the project), and a link to a Google Forms survey where they could enter their responses anonymously. By clicking on the link to the survey, the experts thus gave their implicit informed consent to participate. The Survey Form sent to the experts is available in the OSF repository for this project.⁵⁴ Experts that replied to our email declining to take part in the survey were not contacted further. Any experts that did not explicitly decline to take part were reminded twice, as the survey responses were fully anonymous, and we had no way of linking responses to individual experts. A total of 26 experts (48%) responded to the invitation by filling our survey (14 of them were personal contacts). The experts (self-)reported that they belonged to the following expert groups: four experts in science journalism, four journal editors, seven meta-researchers/experts on preprints, and 11 methodologists.

Response collection and analysis

Experts rated the relevance of each element of the checklist on a five-point Likert scale, with the following response options: extremely irrelevant, mostly irrelevant, neither relevant nor irrelevant, mostly relevant, and extremely relevant. Response data were analysed by computing mean responses per element, using R (Version 4.04). We based our decisions on which elements to keep following the procedure used to establish the CONSORT guidelines for abstracts.⁶⁸ That is, all elements with a mean score of four and above were kept (in the CONSORT for abstracts, this score was eight, as they used a 10-point Likert scale), elements with a mean score between three and four (four not included; between six and seven in the CONSORT guidelines for abstracts criteria) were marked for possible inclusion, and elements with a mean score below three were rejected.

Experts also had the option to provide free-text comments: general additional comments on the checklist elements, suggestions for potentially relevant items that are missing, and suggestions on the structure (a PDF of the survey, including the Likert scales and free-text options is available in the OSF repository for this project⁵⁴). These comments were collected into a single document and responded to in a point-by-point manner akin to a response to reviewers document (also in the OSF repository for this project⁵⁴), arguing our agreement/disagreement with expert comments and how they were addressed in the subsequent draft of the checklist.

Preliminary implementation

Experts rated the relevance In the Preliminary implementation stage we envisaged two workshops for students: one for Bachelors’ students of Psychology at the University of Geneva, and one for Bachelors’ students of Medicine at the University of Zurich. Both workshops were given as invited lectures in standard classes taught to students as part of their respective Bachelors’ courses (as part of the “Scientific skills and competencies in psychology” class at the University of Geneva [in the original French: “Compétences et connaissances scientifiques en psychologie”], and the “Biostatistics for medical professionals” class at the University of Zurich [in the original German: “Biostatistik für Mediziner”]). The workshop content was made clear to the students in advance. Only those students that were enrolled in the above classes as part of their Bachelors’ courses could attend the workshops. Thus, no special consent was required to participate in the workshops. One junior member led the workshop at the University of Geneva, while at the University of Zurich, one junior and one senior member led the workshop. There was no relationship of dependence between either one of these members and the students they administered the workshops to (i.e., neither member was involved in the grading of the students’ course assignments or exams). Both workshops started with a theoretical presentation of the scientific publishing process, what preprints are, and current issues with preprints and peer review (based on the conclusions of the literature review in the present manuscript). Next, the purpose and component parts of the checklist were presented, together with instructions on how to use it for the subsequent in-class exercise. In the exercise, students were split into two groups according to their last names, each given 15-20 minutes to re-read a preprint (they were informed about the exercise and given the preprints to read before the workshop as homework; one group read,⁶⁴ and the other group read)⁶² and use the checklist to evaluate it. The answers were collected anonymously, in an aggregated (non-individual) fashion, via an in-house platform. At the University of Geneva, we used surveys on Votamatic (https://votamatic.unige.ch/) to gather the percentages of students that voted ‘yes’, ‘no’, or ‘partly’ for each superficial-level item, and Padlet (https://unige.padlet.org) to gather optional free text responses to the deep-level items. At the University of Zurich, Klicker (https://www.klicker.uzh.ch) was used to gather the percentages of students that voted ‘yes’, ‘no’, or ‘maybe’ for each superficial-level item, alongside optional free text comments. Once recorded, these percentages were discussed by the whole class, and compared against the researchers’ own evaluation of said preprint. The responses were only analysed inasmuch as percentages of ‘yes’, ‘no’, and ‘partly/maybe’ responses were automatically generated by the respective platforms, during the class, for the purpose of in-class discussion. These responses were not recorded outside of the platform (e.g., on any project team member’s computer), nor were they subject to any formal statistical analyses performed on these responses, and the responses did not influence the content of the checklist in any way. We did not ask any question about the workshop participants’ educational background or level of experience with academic research.

The above workshop format was also adapted for science journalists employed at the Universities of Geneva and Zurich (i.e. the members of the respective Communication Departments). Eventually only the workshop at the University of Geneva was held (and led by the junior member of the team based at the University of Geneva), as the relevant personnel at the University of Zurich did not respond to our requests to hold a workshop. The format was largely the same as that of the workshop for students, except that the initial presentation focused less on the scientific publishing process, and more on issues with preprints and peer review, and included more time for a mutual discussion of said issues. We intended for these to be small workshops open only to a select number of people, on a purely voluntary basis, invited by the main contact person at each University’s communications section. All of the invited parties were informed on the content of the workshop beforehand. Only those individuals that were interested in attending did so and provided verbal assent to participate in the workshop. The same in-house online platform as before (i.e., Votamatic) was used to collect data on percentages of ‘yes’, ‘no’, or ‘partly’ for each superficial-level item of the checklist in an anonymous, aggregated (non-individual) fashion, and this automatic generation of response percentages was the only analysis performed on these data. Deep-level item answers were informally discussed. As before, there were no formal statistical analyses performed on these data. Some informal verbal feedback (not previously solicited) that we received from the participants did influence the content of the checklist, as we detail in the Preliminary implementation section below.

Finally, the content of the workshop for university science journalists was adapted for a fact-checking seminar organised by the Swiss Association of Science Journalists (https://www.science-journalism.ch/event/spring-seminar-2022). Two junior members gave this workshop at the Swiss National Science Foundation headquarters in Bern. Participation was voluntary and open only to individuals that registered to attend the conference at which we were invited to give our workshop as part of the advertised programme. Thus, no special consent was required for participation. We used the same procedure as above, with the exception that a ‘nonsense’ preprint was read and evaluated;⁶⁹ i.e., a manuscript describing a made-up study to prove the point that predatory journals do not screen for quality) and no response data were collected (responses were probed and discussed verbally during the session).

Stage 1 results

First draft of the checklist

The first draft of the checklist was created from April 16 until May 17, 2021, and contained six categories of items: research question, study type, transparency, limitations, study reporting, and research integrity. The research question item asked whether the study mentioned the research question/aim, this being the most basic component of a research study. The study type question asked whether the study type was mentioned, and in the case that it was not, asked users to try and infer what the study type was, with guidance. In transparency, users were supposed to check the existence, availability, and accessibility of a protocol, and of data, code, and materials sharing. The limitations question asked whether any limitations of the study were mentioned, and asked users to try and evaluate any potentially unmentioned limitations (biases, specifically), with guidance. In study reporting, we asked to check for reporting guidelines that were followed explicitly or implicitly. Finally, the research integrity category asked users to check whether ethical approval, conflicts of interest, and contributor roles were reported.

Internal review results

In the first round of internal review, the senior members of our team provided feedback on the contents of the first draft of the checklist. This round revealed that explanations were needed as to the importance of considering each specific item in our checklist, and that both a more ‘superficial level’ and a ‘deeper level’ were necessary to account for all user needs. For these reasons, we expanded the initial checklist, such that each item consisted of a main question, an explanatory section entitled ‘Why is this important’, and a section entitled ‘Let’s dig deeper’. The main questions formed the basis of the checklist, as they were all closed questions that could be answered via the ‘yes’ box next to them. Users could tick the box in full to indicate that the preprint being read passes the question, in part to indicate a ‘maybe’ response, or not at all to indicate that the preprint does not pass the question. This level was also called the ‘superficial level’ of assessment, as the questions could mostly be answered after a quick read of a preprint, and by searching for keywords that appear in the questions. The ‘why is this important?’ section was added in order to increase the pedagogical value of the checklist, which was designed as a teaching tool, such that users could learn about the purpose behind the main questions, and their importance for evaluating research. The ‘let’s dig deeper’ sections were added as an optional part for users that wanted to go beyond the main questions in their evaluation of a preprint, or that wanted to learn more about how to structure their thoughts when evaluating research work. Thus, this section does not have a tick-box, as it usually contains open questions and suggestions. This section cannot stand alone and should be consulted after the main questions and ‘why is this important’ section, which is why we called this the ‘deep level’ of assessment. A full version of the checklist at this stage can be found in the OSF repository for this project.⁵⁴ This was the version of the checklist that we submitted to a pilot testing on high- and low-quality preprints.

Results of the pilot testing

While searching for high- and low-quality preprint examples to apply the checklist to, we discovered that the checklist works best when applied to research with human subjects using primary data (or systematic reviews, meta analyses and re-analyses of primary data). That is, the questions turned out to be ill-posed (unanswerable) for research that did not fall into the above description, such as simulation studies, for example. We decided to indicate this in the introduction section of the checklist.

At the superficial level, the high-quality preprints that we used^61–63 received mostly ‘yes’ and ‘maybe’ responses to the main questions. Only⁶² had a ‘no’ for mentioning/sharing their data/code. The low-quality preprints^11,64,65 also received several ‘yes’ and ‘maybe’ responses, though fewer than the high-quality preprints. Interestingly, the Transparency and Study reporting items all received ‘no’ responses for the low-quality preprints, whereas the high-quality preprints mostly received ‘maybe’ and ‘yes’ responses. This demonstrates both that high- and low-quality preprints differ in terms of how they meet transparency and reporting standards, but also highlights that even high-quality preprints do not necessarily meet all these standards.

At the deep level, high-quality preprints mostly received ‘yes’ responses to the points in the ‘let’s dig deeper’ section, and a few ‘no’ and ‘maybe’ responses. Meanwhile, the low-quality preprints had no clear pattern of responses with many ‘no’, ‘yes’, and ‘maybe’ responses. However, low-quality preprints had more ‘no’ responses than high-quality preprints. At this level of assessment, one could delve into issues with study design, specifically in Limitations, where low-quality preprints performed demonstrably worse than high-quality preprints. Thus, it may be important to consider both levels of assessment when evaluating preprints using the checklist. The final version of the checklist at this stage was completed on October 18, 2021.

Stage 2 results

External expert review summary results

Experts were first asked how relevant they thought each of the six item categories were for assessing preprint quality on a five-point Likert scale: from extremely irrelevant (score of 1) to extremely relevant (score of 5). Here, all categories scored above four, except study reporting which received a 3.96. Next, experts were to rate the relevance of each of the elements per category, including the main questions, and each of the points in the ‘let’s dig deeper’ sections. The results are summarised in Table 1 below. None of the elements has a score lower than three, which meant that none of the elements warranted immediate exclusion. However, several elements, including the entire study reporting category, had scores between three and four that placed them in the ‘possible inclusion’ category.

Summary of external experts’ comments

The full list of free-text comments submitted by the experts and our responses to them is available in the OSF repository for this project.⁵⁴ Overall, the comments revealed enthusiasm about the checklist, but also important criticisms. First, there were concerns that the target audience as it was previously defined (non-scientists) would not be able to adequately use a checklist of the complexity present at the time. Paradoxically, however, there were also many suggestions for additional elements that could further increase complexity, such as: how the study fills the gap in the knowledge, if the study can be fully reproduced, if there is justification for the statistical methodology used, etc. Another prominent criticism was that the checklist inadvertently prioritised randomised controlled trials and could potentially discredit observational studies. Our pilot testing did not find observational studies to be particularly disadvantaged in comparison with randomised controlled trials. However, we did acknowledge that some categories, specifically limitations, appeared more oriented towards randomised controlled trials. One specific comment raised the issue that our checklist did not include COVID-19 specific questions, despite the checklist’s motivation. We thus sought to correct and elaborate these points in the next versions of the checklist.

Some experts had additional ideas, some of which were outside the scope of this project, but others of which were easy to implement. In particular, the suggestion to ask users to check if the manuscript converted into a publication, and to include spin and overinterpretation of results as other examples of biases in the Limitations section. These suggestions were incorporated into the subsequent versions of the checklist.

Second draft of the checklist

The second draft of the checklist⁵⁴ consisted of the following elements: Research question (main question only), study type, transparency (main question on mentioning the protocol, and two ‘let’s dig deeper’ questions on accessing the protocol, and accessing the data), limitations, and research integrity (two main questions on mentioning an ethics approval statement, and conflicts of interest). After expert feedback, we decided to omit the study reporting category, and instead incorporate the reporting guidelines mentioned there in the newly added descriptions of study types in the item study type, to reduce overall complexity, and increase clarity in this section specifically. After comments on the checklist’s complexity, we combined the transparency and research integrity categories and their remaining elements into a new category called ‘transparency and integrity’. Here, in response to a specific comment, we altered the main questions such that they probe if a study protocol, data sharing, materials sharing, ethical approval, and conflicts of interest, are mentioned, whereas the ‘let’s dig deeper’ section asks if the above are accessible (in the aforementioned section, we define what we mean by accessible). In addition to these changes, we realised the utility of looking both at the preprint and the preprint server when using the checklist, as sometimes the preprint does not mention data/materials sharing, but these resources are shared on the server.²⁰ Thus, we added a recommendation into the introduction to consider both sources when using the checklist. In response to the comment on inadvertently disadvantaging observational research, we added disclaimers into the limitations section stating when certain sources of bias do not apply. Specifically, for the control group/condition, randomisation, and blinding elements, we added a clause to the end of each paragraph that states ‘(if your preprint is on an observational study, this item does not apply)’. In response to the lack of a COVID-19 element, we elaborated that, although the state of COVID-19 preprints and their effect on society was our inspiration for the project, our expertise (preprint quality in medicine and psychology) made it difficult to create an adequate COVID-19-specific checklist. With this, we modified the title of the checklist and expanded the introduction, to avoid further confusion. The final version of the checklist at this stage was completed on January 17, 2022. It is available in the OSF repository for this project.⁵⁴ Also, we structured our workshops with students and journalists around issues with preprints and peer review more generally.

Stage 3 results

Final draft of the checklist

In the second internal review round, we kept the four-item structure, most of the text, and visual separation between the superficial and deep levels from the second draft of the checklist. In addition, the wording was clarified and additional explanations were provided where necessary. In transparency and integrity, we added clauses to explain what to do in situations where data and materials are stated to be shared upon request, or if reasons against sharing are mentioned. Specifically, since acquiring data/materials after requesting it from authors that only share upon request happens only in a minority of cases,⁷⁰ we advised that ‘mentioning only that data will be shared ‘upon request’ does not count’. However, if authors mention that they cannot share the data or materials for a specific reason, we advised that ‘mentioning any reasons against sharing also counts [as a ‘yes’]’. In the limitation section, we added examples of spin and overinterpretation as other sorts of biases to look out for. In the introduction, we added the recommendation to check whether the preprint has converted into a publication.

Results of pilot testing

At the superficial level, both high- and low-quality preprints had many positive responses, for both team members that tested the checklist. The elements that differed the most were transparency and integrity, with low-quality preprints having slightly more ‘no’ and ‘maybe’ responses than high-quality preprints. Additionally, both raters agreed that two of the three low-quality preprints did not discuss limitations. This is a slight departure from the prior pilot testing results, in that the difference between high- and low-quality preprints appears to be smaller.

At the deep level, however, the differences were once again well-pronounced, as high-quality preprints had predominantly positive responses, while low-quality preprints had predominantly negative and ‘maybe’ responses. Thus, the deep level seems to be necessary to fully discern between high- and low-quality preprints. Similarly to the prior results, the responses in the transparency and integrity section exposed that even high-quality preprints did not always meet the standards of transparency and integrity. The final version of the checklist at this stage was completed on March 1, 2022.

Preliminary implementation

With an operational checklist, we set out to teach members of our target audience how to use the checklist and to verify if they could use it as intended. To this end, we gave courses including workshops to Bachelor students in Medicine and Psychology at the University of Zurich, and the University of Geneva, respectively. The workshop at the University of Zurich took place on March 11, 2022, while the workshop at the University of Geneva took place on May 9, 2022. For our journalist cohort, we provided a lecture and practical for members of the University of Geneva communications office and scientific information division. This workshop took place on May 19, 2022. We later also presented the checklist at a fact-checking seminar organised by the Swiss Association of Science Journalists on May 31, 2022.

Across all of these classes, except for the fact-checking seminar, we used the same high- and low-quality preprints as practice material, and explained both how to use the checklist, as well as the rationale behind its elements, as stated in our point-by-point response to experts. A few suggestions for improvement nonetheless emerged from the workshop with the journalists at the University of Geneva, as some participants wished to offer feedback. Some participants of this workshop pointed out that the necessity and function of both the superficial and deep level of assessment were not clear. Others had trouble understanding what mention of data and materials sharing counts as a ‘yes’ response and what counts as a ‘no’ response. Finally, one participant suggested that even before using the checklist, one should generally apply more caution when assessing controversial research or findings that sound ‘too good to be true’. We incorporated all of this feedback into the final version of the checklist, which was completed on May 20, 2022.⁵⁴

During post-publication peer-review, it became apparent that our checklist did not address qualitative research at all. Since we have only designed the checklist with quantitative research in mind, we expanded the disclaimer in the Introduction to the checklist to state that it is not optimised for qualitative aspects of research studies. This was the only change to any part of the checklist as a result of peer review, and it resulted in a new version of the checklist completed on December 18, 2023 (see also Table 2).⁵⁴

PRECHECK: A checklist to evaluate preprints on COVID-19 and beyond

Preprints are manuscripts describing scientific studies that have not been peer-reviewed, that is, checked for quality by an unbiased group of scientists in the same field. Preprints are typically posted online on preprint servers (e.g. BioRxiv, MedRxiv, PsyRxiv) instead of scientific journals. Anyone can access and read preprints freely, but because they are not verified by the scientific community, they can be of lower quality, risking the spread of misinformation. When the COVID-19 pandemic started, a lack of understanding of preprints has led to low-quality research gaining popularity and even infiltrating public policy. Inspired by such events, we have created PRECHECK: a checklist to help you assess the quality of preprints in psychology and medicine, and decide their credibility. This checklist was created with scientifically literate non-specialists in mind, such as students of medicine and psychology, and science journalists.

The checklist contains 4 items. Read them and the Why is this important? Section underneath each of them. Check if the preprint you are reading fulfills the item’s criteria - if yes, tick the Yes box on the right. Generally, the more ticks on the checklist your preprint gets, the higher its quality, but this is only a superficial level of assessment. For a thorough, discriminative analysis of a preprint, please also consult the related Let’s dig deeper sections underneath each item. There are no tick boxes for this level of assessment, but you are welcome to make your own notes. When using the checklist, we recommend that you have both the preprint itself, and the webpage on the preprint server where the preprint was posted at hand. You can also check online whether the preprint has already been peer reviewed and published in a journal.

The checklist works best for studies with human subjects, using primary data (that the researchers collected themselves) or systematic reviews, meta-analyses and re-analyses of primary data. It is not ideally suited to simulation studies (where the data are computer-generated) or studies that have a qualitative part (e.g., like interview data, or other data that cannot be easily translated into numbers). In general, if the study sounds controversial, improbable, or too good to be true, we advise you to proceed with caution when reading the study.