Table 4.

Modified Newcastle–Ottawa Scale for cross-sectional studies

Selection (max 3 points)	Representativeness of the sample	1—Truly representative of the average target population (all subjects or random sampling)	1—Somewhat representative of the average target population (not random sampling, but based on solid sampling strategies)	0—Small or biased subgroup of potential respondents	0—No description of the sampling strategy
	Sample size	1—Justified and satisfactory		0—Not justified
	Non-response rate	1—Response rate is satisfactory (> 70%)		0—Response rate is unsatisfactory (<70%)	0—No description of response rate
Comparability (max 2 points)	Comparability of participants	1—Study controls for the single most important factor	1—Study controls for any additional factors	0—Non-responders differ from responders in important ways
Outcome (max 4 points)	Validity of outcomes	1—Independent blind assessment of behavior	1—Medical record review	0—Self-report	0—No description
	Ascertainment of the exposure (risk factor)	2—Validated measurement tool	1—Non-validated tool but tool available or described	0—Non-validated measurement tool and not described
	Statistical test	1—Statistical test is clearly described and appropriate, includes confidence intervals and probability level		0—Statistical test is not appropriate, not described, or incomplete
Selection (max 3 points)	Is the case definition adequate?	1—Yes, with independent validation		0—Yes, with record linkage or based on self-report	0—No description
	Representativeness of the cases	1—Consecutive or obviously representative series of cases		0—Potential for selection biases or not stated
	Selection of controls	1—Community controls		0—Hospital controls	0—No description
	Definition of controls	1—No history of disease (endpoint)		0—No description of source
Comparability (max 2 points)	Comparability of cases and controls on the basis of the design or analysis	1—Study controls for the single most important factor	1—Study controls for any additional factors
Exposure (max 3 points)	Ascertainment of the exposure	1—Secure record	1—Structured interview where blind to case/control status	0—Interview not blinded to case/control status	0—Written self-report or medical record only	0 – No description
	Same method of ascertainment for cases and controls	1—Yes		0—No
	Non-response rate	1—Same rate for both groups		0—Non-respondents described	0—Rate different and no designation
Selection (max 4 points)	Representativeness of the exposed cohort	1—Truly representative of the average population within the studied community	1—Somewhat representative of the average population within the community	0—Selected group of uses (nurses, volunteers)	0—No description of how the cohort was selected
	Selection of the non-exposed cohort	1—Drawn from the same community as the exposed cohort		0—Drawn from a different source as the exposed cohort	0—No description of the source of the non-exposed cohort
	Ascertainment of exposure:	1—Secure record (medical records)		0—Self-report	0—No description
	Demonstration that outcome of interest was not present at start of study	1—Yes		0—No
Comparability (max 2 points)	Comparability of cohorts on the basis of the design or analysis	1—Study controls for the single most important factor	1—Study controls for any additional factors
Outcome (max 3 points)	Assessment of outcome	1—Independent blind assessment	1—Record linkage	0—Self-report	0—No description
	Was follow-up long enough for outcomes to occur?	1—Yes		0—No
	Adequacy of follow up of cohorts	1—Complete follow-up (all subjects accounted for)	1—Subjects lost to follow-up but unlikely to introduce bias (more than 80% retention) or adequate description of those lost to follow-up	0—Follow up Rate < 80% and no description of those lost to follow-up	0—No description of follow up rate