Fig. 2From: Risk of bias in observational studies using routinely collected data of comparative effectiveness research: a meta-research studyThe number of studies at risk of bias due to lack of synchronization. Nineteen (25%) studies had a high risk of bias due to the lack of synchronization. Of these, 14 proposed no solution, and 5 used inadequate methods to address the bias. Six studies inadequately reported to enable the assessment of synchronization. Fifty-two (68%) studies had low risk of biasBack to article page