Table 1

List of criteria for the assessment of the methodological quality of cohort and case-control designed studies

Item	Criteria	V/I*	CH/CC†
*V, criterion on validity/precision; I, criterion on informativeness; †CH, applicable to cohort designed studies; CC, applicable to case-control designed studies.
	Study group
1	Selection before disease was present or at uniform point	V	CH/CC
2	Cases and controls were drawn from the same population	V	CC
3	Participation rate ⩾80% for cases/cohort	V	CH/CC
4	Participation rate ⩾80% for controls	V	CC
5	Sufficient description of baseline characteristics	I	CH/CC
	Assessment of risk factor
6	Exposure assessment was “blinded”	V	CH/CC
7	Exposure was measured identically in study group	V	CC
8	Exposure was assessed before the outcome	V	CH/CC
	Assessment of hip OA
9	Hip OA was assessed identically in study group	V	CH/CC
10	Presence of hip OA was assessed reproducibly	V	CH/CC
11	Presence of hip OA was according to valid definitions	V	CH/CC
12	Classification was standardised	I	CH/CC
	Study design
13	Prospective design was used	V	CH/CC
14	Follow up time ⩾3 years	V	CH
15	Withdrawals ⩽20%	V	CH
16	Information about completers v withdrawals	I	CH
	Analysis and data presentation
17	Frequencies of most important outcomes were given	I	CH/CC
18	Appropriate analysis techniques were used	V	CH/CC
19	Adjusted for at least age and sex	V	CH/CC