Domain		Signalling questions to critical and important criteria	Assessment	Decision
1	Retraction or expression of concern	Is the study retracted?	Check for post‐publication amendments in the systematic search for studies and on the Retraction Watch Database (http://retractiondatabase.org/RetractionSearch.aspx?)	If study is retracted, exclude the study
		Is there an expression of concerns published elsewhere?	Check for expressed concerns on the journal‘s homepage or preprint server	If expression of concerns are published, (1) send a request to the authors or the journal editors or wait until resolution of the concerns and (2) hold the study in awaiting classification until clarification
2	Trial registration	Does the study report a trial registry number?	Check in the publication or study report	If study is not prospectively registered, exclude the study
		Is the study prospectively registered?	Check in the trials register the date of protocol submission and first posted. Prospective registration is defined as registration of a trial before enrolment of the first participant as defined by the WHO. It must be determined whether the registers registered (date first posted) without delay at this point in the pandemic. In case of doubt, check for the date first submitted or the authors must be asked for the submission date.
		Are there any inconsistencies in details such as dates and study methods reported in the publication and in the registration documents?	Compare study dates (enrolment, duration, completion) and methods (study type, allocation, masking) between publication and protocol.	If date of registration is unclear or if prospectively registered, but with inconclusive information, (1) send a request to the authors and (2) hold the study in awaiting classification until clarification
3	Ethics approval	Is an ethics approval reported in the publication?	e.g. the study was authorized by the ethics committee XY located in XY.	If ethics approval or participants’ consent is not adequate, exclude the study. If ethics approval or participants’ consent is unclear or incomplete, (1) send a request to the authors and (2) hold the study in awaiting classification until clarification.
		Is an ethics approval number reported?	Check in the publication, study report and study protocol
		Is the name and location of the ethics committee reported?	Check in the publication, study report and study protocol
		Does a nationally recognized ethics committee as defined in the country’s clinical trial regulations give the ethics committee approval?	Check the ethics committee on the WHO list of national ethics committees (https://apps.who.int/ethics/nationalcommittees/) and the specific regulations for the country on NIH Clinical Trials Regulation website (https://clinregs.niaid.nih.gov/country/mexico#_top).
		Does the study require written informed consent from participants?	Check in the publication, study report and study protocol
4	Study authorship	Are the authors’ affiliations and countries the study is reported to have taken place in consistent?	Check in the publication, study report and study protocol	If study authorship is unclear, (1) send a request to the authors and (2) hold the study in awaiting classification until clarification. If study authorship is still not plausible after contacting the authors,exclude the study.
		Are countries specified in different parts of the article or as compared to the trials registry consistent?	Check in the publication, study report and study protocol
		Is the number of authors plausible for the study design (e.g. a single author article reporting a randomized controlled trial is impossible)?	Check in the publication, study report and study protocol
5	Methods reporting	Is the study design (e.g. randomization) reported in sufficient detail?	It has to be clear that the study was truthfully randomized. The method used for the randomization must be described and the process must lead to a random allocation of the participants. The sole designation "randomized study" is not sufficient.	If study design is not reported in sufficient detail, (1) send a request to the authors and (2) hold the study in awaiting classification until clarification. If study turns out to be non‐randomized following author contact, exclude the study.
		Are baseline details reported in sufficient detail to assess whether randomization worked properly?	Check whether patients characteristics, e.g. risk factors for COVID‐19 (age, gender, comorbidities) and co‐interventions, are reported
6	Results	Is the number of patients recruited within the timeframe with the condition plausible?	Check in the publication. Justify the decision based on clinical experience. The decision should be verifiable.	If study results are not plausible, (1) send a request to the authors and (2) hold the study in awaiting classification until clarification. If, after contacting the author, it turns out that study results are not plausible or fabricated,exclude the study.
		Is there a realistic response rate or number of participants lost to follow up? In cases with zero losses to follow‐up, is there a plausible explanation (e.g. small number of participants, short‐term follow‐up)?
		Is the study free from results that could be implausible (e.g. massive risk reduction, unexpected outlier data, unusual frequency of an outcome)?
		Does the number of participants (e.g. women) in each group coincide with the reported randomization method (e.g. block randomization)?	Check in the publication, study report and study protocol
		Is there no noteworthy overlap in text/data with other published articles by the same or different authors without explanation?
		Is there no excessive similarity or difference in the characteristics of the study participants between groups?
		Are there no discrepancies between data reported in figures, tables, and text?
		Are there no calculation errors (e.g. number of participants, percentages, proportions)?