Table 2 Study quality scores.

Study reference	Allocation to intervention group	Assigned intervention concealed before allocation	Outcomes of participants who withdrew described + included in analysis	Outcome assessors blinded	Inclusion/exclusion criteria clearly defined?	Groups comparable at entry	Interventions clearly defined	Definition outcome measures	Surveillance period active and of clinically appropriate duration	Total score	Quality rating
Emery14	1	0	2	0	2	0	2	1	2	10	M
Grace13	0	0	1	0	1	1	2	1	2	8	P
Heidt15	2	0	0	2	1	0	2	2	2	11	M
Hewett19	0	0	1	0	1	0	2	2	2	8	P
Junge16	1	0	1	0	1	0	2	2	2	9	M
Mandelbaum20	0	0	0	0	2	1	2	2	2	9	M
McIntosh17	1	0	0	0	1	0	2	2	2	8	P
Olsen18	1	0	1	2	2	2	1	2	2	13	M
Webster12	0	0	0	0	0	0	2	1	2	5	P
Wedderkopp21	1	0	0	0	2	2	1	2	2	10	M
Wedderkopp22	1	0	2	0	1	2	1	1	2	10	M
Yang11	0	0	0	0	0	1	2	1	2	6	P

M, moderate; P, poor.