Table 2: Comparison of results retrieved through the 37 search strategies, considering use of MeSH and EMTREE terms separately or in association, with variations, in the MEDLINE database (via PubMed).

Use of MeSH and EMTREE terms separately or in association, with variations		Equal numbers of results retrieved (%)	Greater number of results retrieved with the first variable † (%)	Smaller number of results retrieved with the first variable † (%)	P-value
MEDLINE via PubMed	MeSH† versus MeSH + EMTREE	3 (8.1)a	0 (0.0)b	34 (91.9)b	P < 0.0001
	EMTREE† versus MeSH + EMTREE	15 (40.6)a	2 (5.4)b	20 (54.0)a	P < 0.0001
	MeSH† versus EMTREE	0 (0.0)a	12 (32.4)b	25 (67.6)c	P < 0.0001

^†First variable is the one that is quoted first in the comparison of interest. a, b, c = values followed by the same letter did not differ significantly.