Table 2.

Study quality summary.

First author (Ref)	Clear identification of study population	Clear definition of outcome and outcome assessment	Independent Assessment of outcome parameters	No selective loss during followup	Important confounders and/or prognostic factors indentified	Adjusted odds ratio (specific adjusters)
Marcus et al. [7]	Yes	Yes	Yes	Yes	Yes	0.75 (age, gender)
Go et al. [16]	Yes	Yes	Yes	Yes	Yes	Not provided
Alonso et al. [17]	Yes	Yes	Yes	Yes	Yes	0.59 (age, gender)
Afzal et al. [18]	Yes	Yes	No	Yes	Yes	Not provided
Ruo et al. [19]	Yes	Yes	Yes	Yes	Yes	0.51 (age, gender, Comorbid conditions, medications)
Winkelmayer et al. [20]	Yes	Yes	Yes	Yes	Yes	Not provided
Upshaw Jr. [21]	Yes	Yes	Yes	Yes	Yes	Not provided
Shen et al. [22]	Yes	Yes	Yes	Yes	Yes	0.49 (age, gender)
Smith et al. [23]	Yes	Yes	Yes	Yes	Yes	0.64 (unclear)
Lahiri et al. [24]	Yes	Yes	Yes	Yes	Yes	0.54 (age, gender, comorbid conditions)