Table 2.

Risk of bias assessment using Newcastle-Ottawa Scale for observational studies.

			Chan et al. (12)	Sarratt et al. (13)	Siontis et al. (11)
Selection	Representativeness of the exposed cohort	Representative or somewhat representative of average dialysis patients in community (age/risk of stroke and bleeding)	*	*	*
	Selection of the non-exposed cohort	Drawn from the same community as the exposed cohort	*	*	*
	Ascertainment of exposure	Secure record, structured interview	*	*	*
	Demonstration that outcome of interest was not present at start of study	Stroke or bleeding due to anticoagulant	–	–	–
Comparability	Comparability of cohorts on the basis of the design or analysis	Study controls for renal function	*	*	*
		Study controls for any additional factors (history and risk of stroke and bleeding)	*	*	-
Outcome	Assessment of outcome	independent blind assessment or record linkage	*	*	*
	Was follow-up long enough for outcomes to occur	Follow-up > 1 year	–	–	*
	Adequacy of follow up of cohorts	Complete follow up (all subjects accounted for) or subjects lost to follow up unlikely to introduce bias	*	*	*
Score			7	7	7

^*Means equal to one point score.