The contribution of databases to the results of systematic reviews: a cross-sectional study

Table 4 Impact of selective searching on results of meta-analyses from acute respiratory infections

		Original meta-analysis				Meta-analysis based on studies identified by selective search
Case	Summary measure	Number of trials	Effect size	Lower CI	Upper CI	Number of trials	Effect size	Lower CI	Upper CI	% of trials identified	% change in effect size
Medline + BIOSIS (changes in 17 of 57 meta-analyses)
1^a	MD	5	−21.29	−29.59	−13	1	−22.9	−41.34	−4.46	20	7.0
2^a	MD	35	−1.24	−1.54	−0.94	26	−1.42	−1.77	−1.06	74	12.7
3^a	MD	24	−0.45	−0.96	0.05	19	−0.25	−0.9	0.39	79	44.7
4^a	RD	2	−0.13	−0.21	−0.05	1	−0.16	−0.26	−0.05	50	18.8
5^a	RD	3	−0.05	−0.12	0.02	1	−0.04	−0.14	0.06	33	20.0
6	MH OR	6	0.27	0.15	0.50	3	0.19	0.08	0.46	50	29.6
7^{a, b}	MH OR	7	0.35	0.12	1.01	6	0.26	0.12	0.6	86	25.7
8^a	RR	2	0.48	0.17	1.34	0	-	-	-	0	-
9^{a, b}	SMD	8	0.49	0.16	0.81	6	0.51	0.1	0.93	75	3.9
10	MD	3	0.5	0.10	0.90	2	0.43	−0.01	0.87	67	14.0
11	RR	6	0.67	0.50	0.89	5	0.75	0.55	1.04	83	10.7
12	RR	25	0.9	0.80	1.01	22	0.91	0.8	1.02	88	1.1
13^a	RR	6	0.95	0.59	1.51	3	0.96	0.82	1.11	50	1.0
14^{a, b}	RR	29	0.95	0.92	0.98	19	0.96	0.94	0.99	66	1.0
15^{a, b}	RR	15	1.09	0.64	1.85	13	0.9	0.54	1.49	87	17.4
16^a	RR	2	1.32	0.87	2.00	0	-	-	-	0	-
17	RR	15	1.82	0.98	3.38	14	1.97	1.06	3.64	93	7.6
Medline + Embase (changes in 12 of 57 meta-analyses; data below show cases where results were different from Medline + BIOSIS results above^b)
7	MH OR	7	0.35	0.12	1.01	4	0.14	0.04	0.53	57	60.0
9	SMD	8	0.49	0.16	0.81	6	0.4	0.07	0.73	75	18.4
14	RR	29	0.95	0.92	0.98	19	0.97	0.94	1	66	2.1
15	RR	15	1.09	0.64	1.85	14	0.96	0.58	1.57	93	11.9

^acases where results also changed for Medline + Embase; ^bcases where results were different between Medline + BIOSIS and Medline + Embase analyses
CI confidence interval, MD mean difference, MH OR Mantel Haenszel odds ratio, RD risk difference, RR risk ratio, SMD standardized mean difference

ISSN: 1471-2288