Table 2.

Methodological quality of cohort studies included in the meta-analysis*.

First author, publication year	Representativeness of the exposed cohort	Selection of the unexposed cohort	Ascertainment of exposure	Outcome of interest not present at start of study	Control for important factor or additional factor†	Assessment of outcome	Follow-up long enough for outcomes to occur‡	Adequacy of follow-up of cohorts§	Quality
McBane et al. (2016)	☆	☆	☆	☆	☆	☆	☆	☆	Low risk of bias
Angelini et al. (2018)	☆	☆	☆	☆	☆	☆	—	☆	Moderate risk of bias
Ageno et al. (2016)	☆	☆	☆	☆	☆☆	—	☆	☆	Low risk of bias

*A study could be awarded a maximum of one star for each item except for the item control for important factor or additional factor. The definition/explanation of each column of the Newcastle–Ottawa scale is available from http://www.ohri.ca/programs/clinical_epidemiology/oxford.asp.

^†A maximum of two stars could be awarded for this item. Studies that controlled for anticoagulation treatment for at least 3 months received one star, whereas studies that controlled for other important confounders received an additional star.

^‡A cohort study with a follow-up time >6 months was assigned one star.

^§A cohort study with a follow-up rate >75% was assigned one star.