Table 1.

Criteria list for the assessment of study quality, modified from Lievense et al[15,16]

Item	Criteria	C/CC/CS†
Study population
1	Selection at uniform point	C/CC/CS
2	Cases and controls drawn from the same population	CC
3	Participation rate >80% for cases/cohort	C/CC
4	Participation rate >80% for controls	CC
Assessment of risk factor
5	Exposure assessment blinded	C/CC/CS
6	Exposure measured identically for cases and controls	CC
7	Exposure assessed according to validated measures	C/CC/CS
Assessment of outcome
8	Outcome assessed identically in studied population	C/CC/CS
9	Outcome reproducibly	C/CC/CS
10	Outcome assessed according to validated measures	C/CC/CS
Study design
11	Prospective design used	C/CC
12	Follow-up time ≥12 months	C
13	Withdrawals <20%	C
Analysis and data presentation
14	Appropriate analysis techniques used	C/CC/CS
15	Adjusted for at least age, and gender	C/CC/CS

^†C = applicable to cohort studies, CC = applicable to case-control studies, CS = applicable to cross-sectional.