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Table 2 Systematic review methods of therapeutic meta-analyses published in 2013 and including non-randomized studies (n = 188)

From: Meta-analyses including non-randomized studies of therapeutic interventions: a methodological review

Characteristic Included NRSI only Included NRSI&RCTs All Meta-analyses
(n = 69) (n = 119) (n = 188)
No (%) No (%) No (%)
Search strategy    
No. of electronic databases searched, median [IQR] 3 [24] 3 [3, 4] 3 [3, 4]
  > 2 databases searched 51 (74) 96 (81) 147 (78)
Electronic databases searcheda    
 Medline/PubMed/Ovid 69 (100) 118 (99) 187 (99)
 EMBASE 52 (75) 97 (82) 149 (79)
 Cochrane 45 (65) 81 (68) 126 (67)
 Web of science/web of knowledge 14 (20) 22 (18) 36 (19)
Time-frame of search strategy reported 62 (90) 109 (92) 171 (91)
Time end of search-publication date (months), median [min-max] 10 [0–24] 9 [1–51] 10 [0–51]
Search strategy provided for at least one database 18 (26) 44 (37) 62 (33)
Searched reference lists for relevant studies 57 (83) 105 (88) 162 (86)
Hand searched journals 5 (7) 7 (6) 12 (6)
Searched for grey literaturea 23 (33) 49 (41) 72 (38)
 Conference abstracts 14 (20) 27 (23) 41 (22)
 Registries (eg, ClinicalTrials.gov) 8 (12) 25 (21) 33 (18)
 Experts 6 (9) 9 (8) 15 (8)
No restriction by language reported 20 (29) 62 (52) 82 (44)
Study selection    
Duplicate study selection 47 (68) 84 (71) 131 (70)
Methodological quality/risk of bias    
Assessment of MQ/RoB 47 (68) 88 (74) 135 (72)
Tools used for RCTsa    
 Cochrane RoB Tool [41] NA 42 (35) NA
 Jadad scale [42] NA 22 (18) NA
 GRADE [43] NA 9 (8) NA
 Other NA 21 (18) NA
 Authors made their own tool NA 3 (3) NA
 Unclear NA 7 (6) NA
Tools used for NRSIa    
 Newcastle-Ottawa scale [44] 25 (36) 43 (36) 68 (36)
 GRADE [43] 5 (7) 8 (7) 13 (7)
 Cochrane RoB Tool [41] 3 (4) 7 (6) 10 (5)
 Other tools 13 (19) 24 (20) 37 (20)
 Authors made their own tool 6 (9) 6 (5) 12 (6)
 Unclear 3 (4) 9 (8) 12 (6)
Confounding taken into account in risk of bias 13 (19) 20 (17) 33 (18)
Same tool used for RCTs and NRSI NA 27 (23) NA
Duplicate MQ/RoB assessment 30/47 (64) 57/88 (65) 87/135 (64)
Data extraction    
 Duplicate data extraction 52 (75) 86 (72) 138 (73)
 Contact authors for clarification or additional results 18 (26) 43 (36) 61 (32)
  1. Data are no. (%), unless indicated. IQR interquartile range; MQ methodological quality; NRSI non-randomized studies of interventions; RCTs randomized controlled trials; Cochrane RoB Cochrane risk of bias tool; NA Not applicable
  2. aMore than one item could have been reported for each meta-analysis