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Table 2 Number of articles according to design in different medical journals. Percentages in rounded figures. §1994–2002, ¢2001, ¥August–December 2001, *November–December 2001

From: Levels of evidence in endoscopic research: a longitudinal survey

  JAAGL§ Surgical endoscopy¢ Surgery¢ AJOG¥ AJOG surgical¥ BMJ* NEJM* Total
  N (%) N (%) N (%) N (%) N (%) N (%) N (%)  
Systematic review 1 (0.2) 2 (1.2) 0 (0) 1 (3.7) 0 (0) 1 (10) 0 (0) 5
Randomized clinical trials 48 (8.8) 11 (6.5) 10 (10) 12 (44.4) 4 (23) 5 (50) 14 (82) 104
Non-randomized controlled trials 65 (12) 27 (16) 34 (34) 5 (18.5) 5 (29) 4 (40) 2 (12) 152
Case reports or case series 432 (79) 130 (76.5) 55 (56) 9 (33.3) 8 (48) 0 (0) 1 (6) 653
Total 546 170 99 27 17 10 17 886