1. Quality of studies.

Study	Randomisation	Allocation conceal.	Treatment blinding	ITT analysis	Total drop‐out	Selective drop‐out	Blind outcome‐assess	Overall quality
	A=adequate B=unknown or inadequate	A=adequate B=unknown or inadequate	A=adequate B=blinding but method unclear C=non‐blinded, inadequate, or unknown	A=adequate B=ITT inadequate C=unclear or no reported data on drop‐out or loss to follow up	A<15% B>/=15% or unknown	A=difference in drop‐out rate in main groups<10% B>/=10% or unknown	A=adequate B=mentioning of blinding but exact method unclear C=non blinded, inadequate or unknown	A=all quality criteria met B=one or more quality criteria only partially met C=one or more criteria not met
Alloway 1993	B	B	C	C	B	A	C	C
Man 2007	A	A	B	A	A	B	C	B
Siegel 1994	B	B	C	C	A	A	C	C