Table 1.

Quality control criteria for methodology of the studies

	Score
Criterion	0	1	2
Method
Randomization	Not randomized		Randomized
Blinding	Not blinded		Double-blind
Analysis	Other		Intention-to-treat
End-point mortality	No mortality as end point	Secondary end-point	Primary end-point
Population
Patient selection	Selected patients or unclear	Consecutive eligible patients
Comparability at baseline	No or unclear	Yes
Extent of follow-up	Incomplete	Complete
Intervention
Treatment protocol	Unclear	Reproducible
Co-interventions	Not described	Described, but not equal or unclear	Well described and equal
Crossover	Not described	>10%	<10%