Olsen 1993.

Methods	Design of RCT: parallel‐group clinical trial                                                    Power calculation: not stated                                                  No blinding used                                                         Time of follow‐up: not stated                                                  60 women among 151 patients with diagnosis of appendicitis. 91 not included because of exclusion criteria or because a surgeon with laparoscopic skills was not available                                                    No participants excluded after random assignment                                                      Participants lost to follow‐up: not clearly stated                                                    60 women analysed                                                   Single centre: Department of Surgery, Kolding County Hospital, Kolding, Denmark                                                 Enrollment from 1 January 1988 to 26 November 1991       Source of funding: not stated Ethical issues: approved by the local ethics committee Method to establish definitive diagnosis: visual examination of appendix in laparoscopic group. Not clearly stated in conventional group
Participants	"Women aged 15‐56 years with clinical signs of acute appendicitis were studied"                                                     Participants with signs of diffuse peritonitis, with a previous diagnosis of diffuse peritonitis and with more than two previous lower laparotomies excluded                               Mean age (range), years: 25.3 (15 to 54) in laparoscopy group, 25.8 (15 to 56) in direct operation
Interventions	Laparoscopy versus direct operation                                        Appendicectomy performed through a transverse incision in the right iliac fossa Laparoscopy performed under general anaesthesia: no other data provided                                                  Appendicectomy performed when acute appendicitis was confirmed and when a diagnosis of appendicitis could not be excluded                                               Appendicitis excluded if a normal appendix could be seen throughout its length. If other abnormalities were found, appropriate treatment given
Outcomes	Postoperative stay: not defined; stated in methods and reported Complications and readmission: not validated; stated in methods and reported Final diagnosis: only reported
User defined 1
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Text: trial performed in a randomised fashion. No other description provided about how randomisation was generated
Allocation concealment (selection bias)	Unclear risk	Text: nothing stated about how concealment was achieved
Blinding (performance bias and detection bias) All outcomes	High risk	Open RCT
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Not clear whether follow‐up was similar in the two groups. All randomly assigned participants analysed
Selective reporting (reporting bias)	Unclear risk	Protocol of the study not available
Free of differential verification bias	Unclear risk	Definitive diagnosis not done with the same reference standard in both groups
Free of partial verification bias	Unclear risk	Non‐random set of participants not undergoing the reference standard
Free of Incorporation Bias	High risk	Index test incorporated as the reference standard in the laparoscopic group
Other bias	Unclear risk	All baseline characteristics not reported