1. Research objective and study rationale
a. What is the primary research objective of this study?
b. What is the rationale for this objective (i.e., the reason(s) that this objective is important to achieve)?
c. In terms of public health importance and contribution to knowledge, how strong is the rationale for this study and how well is it presented by the authors (e.g., conceptual framework, supporting evidence, logic)?
d. How well grounded is the rationale in the published literature (biological, epidemiological)?
2. Key variables, measures, and data collection modes
a. What are the key variables and what are their roles (e.g., primary outcome [“disease”] or dependent variables, “exposure” or study factors, major potential confounders and other covariables)?
b. How are these variables defined and measured?
c. What are the major modes by which data are being collected? (e.g., self-administered questionnaire, interviewer-administered questionnaire, medical record review, biological specimens, etc.)
d. How suited are these variables, their definitions, their measurement methods, and the data collection modes for the objectives and rationale of this study? Would other ones have been better for meeting the objectives? If yes, which variables and/or methods and why?
3. Study conduct and quality control
a. How has the study population been recruited (e.g., patients in a clinic, volunteers to advertisements, random digit dialing, area sampling of households, etc.)? If different groups of participants are recruited through different mechanisms (e.g., cases and controls, exposed and unexposed), provide this information for each primary group).
b. What steps were taken to minimize non-participation and selective factors in recruitment? In retention? How effective were these steps?
c. How successful, overall, was the data collection? What major steps were taken to improve and
document the accuracy of the data collected?
4. Study design and study population
a. Identify the important design features of the study, such as its basic design, or architecture (e.g., case-control, cohort, etc.) and how the design is implemented (e.g., incident vs. prevalent cases, randomization by group, whether data are collected multiple times, what follow-up or any is involved, how follow-up if any is carried out, etc.])
b. Compared to other reasonable choices, what are the advantages and disadvantages of this study design and its features for the specific objective(s) or question(s) of this study?
c. What is the study population for this investigation?
d. What are the major eligibility criteria (inclusion and/or exclusion criteria)?
e. How suited is this choice of study population, including eligibility criteria, for the objectives of the study?
5. Data analysis
a. What are the primary data analysis strategies and/or methods used in the study (e.g., stratified analysis, mathematical modeling, graphical analysis)?
b. How are the primary variables coded for analysis? (e.g., as binary or dichotomous variables, in categories, as ordered categories, as counts, as continuous measures?)
c. What were the primary statistical parameters (measures) estimated in the data analysis (e.g., means, prevalences, incidences, incidence rate ratios, odds ratios, survival curves)?
d. How well suited is the choice of these parameters to the objectives of the study? Are there other parameters that you think should have been estimated?
e. How many participants are included in the primary analyses, and what percentage do they
constitute of the people who were eligible and selected for inclusion? Have a substantial number of observations been dropped from the analyses? Do drop-outs pose any limitations to the final conclusion?
f. How well do the authors deal with issues of multi-causation (e.g., measurement of and control for potentially confounding variables, investigation of important interactions)? Do the authors analyze the data separately in respect to a major variable to assess similarity or differences?
a. What are the main findings, including both those related to the primary study question(s) and other important results?
b. Are there particular results you regard as most important?
c. How well have the authors reported and presented their findings?
d. Are there additional results or analyses that you believe should have been reported, data that should have been shown?
e. Are extraneous results presented?
7. Potential concerns in interpreting the findings
a. How completely do the authors account for the disposition of all prospective members of the study population (e.g., persons sampled but not contacted, refusals, exclusions from analysis, etc.)
b. Does the study population seem to reflect the target population well? What sources of selection bias, if any, are likely to be a problem?
c. What are the major possible sources of bias and other threats to validity that are important for interpreting the findings?
d. How well did the authors discuss these threats to validity? Did the authors present them objectively, evaluate their likely importance, and provide evidence in support of that evaluation? Did the authors conduct any specific analyses to evaluate reliability, validity, selection bias, social desirability, or information bias? What were the results of these analyses?
8. Conclusions, implications, and recommendations
ff. What are the primary conclusions? Are they stated clearly?
a. How well are they supported by the findings and discussion?
b. How directly do the conclusions relate to the primary study objective and rationale?
c. How well did the authors address implications of their study and/or give insightful recommendations for next steps.
9. Overview of strengths and limitations
a. What were the key strengths of this study in regard to its objective and accomplishments?
b. Has the study taken advantage of new methodology?
c. Do these strengths or new methodology advance the field? How?
d. What were the key limitations of this study in regard to its objective(s) and
e. Are these limitations shared by other studies of this topic?
f. What would be needed to overcome these limitations?
10. Linkage with previous knowledge
a. How well did the authors compare their results to the findings from other relevant studies?
How well did the authors discuss reasons for differences between previous findings and their own?
b. How well did the authors evaluate the evidence concerning the study objective or question in regard to possible biological or other mechanisms that could account for their findings and other criteria for causal inference (for this question, please ignore concerns about bias)?
c. How relevant and responsive to the study rationale was this discussion?
d. In what ways, if any, have the authors advanced previous knowledge?