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Table 5 Impact of selective searching on results of meta-analysis from infectious diseases

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

  

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 + Embase (changes in 9 of 31 meta-analyses)

1a, b

MD

35

−24.76

−33.61

−15.91

30

−22.22

−31.85

−12.6

86

10.3

2a, b

RR

5

0.41

0.11

1.64

3

NE

-

-

60

-

3

RR

4

0.48

0.35

0.65

3

0.57

0.29

1.09

75

15.8

4a, b

RR

21

0.53

0.49

0.57

16

0.51

0.46

0.56

76

3.8

5a, b

MH OR

11

0.59

0.45

0.79

7

0.61

0.41

0.89

64

3.3

6a

RR

3

0.62

0.19

2.04

2

0.56

0.14

2.14

67

9.7

7a, b

MH OR

10

0.68

0.49

0.95

8

0.59

0.41

0.86

80

13.2

8a

RR

8

0.71

0.62

0.80

6

0.72

0.64

0.82

75

1.4

9a

RR

13

0.99

0.90

1.09

11

0.95

0.86

1.05

85

4.0

Medline + BIOSIS (changes in 8 of 31 meta-analyses; data below show cases where results were different from Medline + Embase results aboveb)

1

MD

35

−24.76

−33.61

−15.91

29

−23.18

−32.94

−13.42

83

6.4

2

RR

5

0.41

0.11

1.64

3

NE

-

-

60

-

4

RR

21

0.53

0.49

0.57

17

0.49

0.44

0.54

81

7.5

5

MH OR

11

0.59

0.45

0.79

8

0.64

0.48

0.87

73

7.8

7

MH OR

10

0.68

0.49

0.95

8

0.54

0.34

0.86

80

20.6

  1. CI confidence interval, MD mean difference, MH OR Mantel Haenszel odds ratio, NE not estimable (all study groups had zero counts); RR risk ratio
  2. acases where results also changed for Medline + BIOSIS; bcases where results were different between Medline + BIOSIS and Medline + Embase analyses