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Table 1 General characteristics of the 80 included meta-epidemiological (ME) studiesa

From: Trial-level characteristics associate with treatment effect estimates: a systematic review of meta-epidemiological studies

General characteristics

No. of ME studyb

% (95% CI)

Median publication year, range

2013

1995–2020

Type of publication

 Journal article

76

95 (90 to 100)

 Agency report

4

5 (0 to 10)

Journal articles

 General journal

26

32 (22 to 43)

 Medical specialty journal

50

62 (52 to 73)

 Epidemiology/biostatistics

26

32 (22 to 43)

Involvement of epidemiologists/statisticiansc

56/77

73 (63 to 83)

Funding sourcesc

 Public

48/64

75 (64 to 86)

 Private

2/64

3 (0 to 8)

 None

14/64

22 (12 to 32)

Type of interventionc

 Pharmacological intervention

5/62

8 (1 to 15)

 Non-pharmacological intervention

6/62

10 (2 to 17)

 Both

51/62

82 (72 to 92)

Medical conditionsc

 Various medical areas

48/72

67 (56 to 78)

 Diseases of the digestive system

9/72

12 (5 to 20)

 Pregnancy, childbirth or the puerperium

5/72

7 (1 to 13)

 Diseases of the musculoskeletal system or connective tissue

5/72

7 (1 to 13)

 Otherse

5/72

7 (1 to 13)

Top five trial-level characteristics evaluated

 Allocation concealment

30

38 (27 to 48)

 Sequence generation

24

30 (20 to 40)

 Double blindingd

19

24 (14 to 33)

 Blinding of outcome assessors

18

22 (13 to 32)

 Blinding of participants

13

16 (8 to 24)

Type of outcome measuref

 Binary

60

75 (65 to 85)

 Continuous

37

46 (35 to 57)

 Time-to-event

5

6 (1 to 12)

Type of study design for literature search

 Collection of meta-analyses

63

79 (70 to 88)

 Collection of trials

11

14 (6 to 22)

 Combination of previously published ME studies

6

8 (2 to 13)

ME studies quantitatively synthesized a difference of treatment effect

68

85 (77 to 93)

  1. aValues are numbers of ME studies, percentage (95% confidence interval) unless stated otherwise. bDenominators are 80 unless stated otherwise. cDenominators are not equal to 80 as some ME studies did not report relate information
  2. dDescribed as double-blinding or ≥ 2 key groups (participants, personnel, outcome assessors) were blinded. eOthers includes neoplasms (2, 2.8%), mental, behavioural or neurodevelopmental disorders (1, 1.4%), diseases of the nervous system (1, 1.4%), and symptoms, signs or clinical findings, not elsewhere classified (1, 1.4%). fTotal number was over 80, due to more than one type of outcome measure was used in some ME studies