Table 2.

Risk of bias assessment and quality of included studies

	Selection		Comparability		Outcome		Overall quality
Observational studies1
Ahmad et al[13]	++		+		++		5
Kooby et al[14]	+++		++		++		7
Carr et al[15]	++		++		++		6
Salem et al[16]	++++		++		+++		9
Lance et al[17]	+++		++		++		7
Moreno-Luna et al[18]	++++		++		+++		9
El Fouly et al[20]	++		+		+++		6
Akinwande et al[22]	++		+		++		5
Randomized controlled trials2
	1	2	3	4	5	6	7
Pitton et al[19]	L	L	L	U	L	L	L	H
Kolligs et al[21]	L	H	U	U	H	L	L	M

¹Study quality assessment performed by means of Newcastle/Ottawa scale (each asterisk represents if the respective criterion within the subsection was satisfied);

²Cochrane Collaboration’s tool for assessing the risk of bias across 7 domains: (1) random sequence generation; (2) allocation concealment; (3) blinding of participants and personnel; (4) blinding of outcome assessment; (5) incomplete outcome data; (6) selective reporting; and (7) other bias. L: Low; H: High; U: Unclear; M: Moderate.