Table 3.

Newcastle–Ottawa Scale (adapted for cross-sectional studies)

	Q1	Q2	Q3
Selection (maximum 3 points)	Representativeness of the sample: a) Truly representative of the average in the target population (all subjects or random sampling) (1 point) b) Somewhat representative of the average in the target population (nonrandom sampling) (1 point) c) Selected group of users d) No description of the sampling strategy	Nonrespondents: a) Comparability between respondents and nonrespondents characteristics is established, and the response rate is satisfactory (1 point) b) The response rate is unsatisfactory, or the comparability between respondents and nonrespondents is unsatisfactory c) No description of the response rate or the characteristics of the responders and the nonresponders	Ascertainment of the exposure (risk factor): a) Validated measurement tool (1 point) b) Nonvalidated measurement tool, but the tool is available or described c) No description of the measurement tool
Comparability (maximum 2 points)	The subjects in different outcome groups are comparable, based on the study design or analysis. Confounding factors are controlled: a) The study controls for the most important factor (select one) (1 point) b) The study control for any additional factor (1 point)
Outcome (maximum 2 points)	Assessment of the outcome: a) Independent blind assessment (1 point) b) Record linkage (1 point) c) Self report d) No description	Statistical test: a) The statistical test used to analyze the data is clearly described and appropriate, and the measurement of the association is presented, including confidence intervals and the probability level (p value) (1 point) b) The statistical test is not appropriate, not described or incomplete