Table 1.

Results of systematic search

Stage	Action	Reviewer	No of citations selected
1	Search*	RR	6827
2	Duplicates and other topics removed	RR	2903
3	Exclusion against criteria (see text)	RR and HW	77
4	Exclusion on basis of full text	RR and HW	1

^*Searches according to strategies devised for studies on diagnostic accuracy by Bachmann et al. J Am Med Inform Assoc 2002;9: 653-412386115 and J Med Libr Assoc 2003;91: 63-8.