title: Evidence of surgical outcomes fluctuates over time: results from a cumulative meta-analysis of laparoscopic versus open appendectomy for acute appendicitis.
abstract: BACKGROUND
  In surgical trials, complex variables such as equipment development and surgeons' learning curve are involved. The evidence obtained in these trials can thus fluctuate over time. We explored the stability of the evidence obtained during surgery by conducting a cumulative meta-analysis of randomized controlled trials for open and laparoscopic appendectomy.
  
  
  METHODS
  We conducted a cumulative meta-analysis of randomized controlled trials comparing laparoscopic appendectomy with open appendectomy for acute appendicitis, a topic with the greatest number of trials in the gastroenterological surgical field. We searched the MEDLINE (PubMed), EMBASE, and CINAHL databases up to September 2014 and reviewed the bibliographies. Outcomes were the incidence of intra-abdominal abscess, incidence of wound infection, operative time, and length of hospital stay. We used the 95 % confidence interval (95 % CI) of effect size for the significance test.
  
  
  RESULTS
  Sixty-four trials were included in this analysis. Of the 51 trials addressing intra-abdominal abscesses, our cumulative meta-analysis of trials published up to and including 2001 demonstrated statistical significance in favor of open appendectomy (cumulative odds ratio [OR] 2.35, 95 % CI 1.30-4.25). The effect size in favor of open procedures began to disappear after 2001, leading to an insignificant result with an overall cumulative OR of 1.32 (95 % CI 0.84-2.10) when laparoscopic appendectomy was compared with open appendectomy.
  
  
  CONCLUSIONS
  The evidence regarding treatment effectiveness changed over time, after treatment effectiveness became significant in trials comparing laparoscopic and open appendectomy. Observing only the 95 % confidence interval of effect size from a meta-analysis may not provide conclusive results.
authors.affiliation: Department of Community Medicine, Mie University School of Medicine, 2-174 Edobashi, Tsu, Mie, 514-8507, Japan.
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Ukai
authors.affiliation: Department of Family Medicine, Mie University School of Medicine & Graduate School of Medicine, 2-174 Edobashi, Tsu, Mie, 514-8507, Japan. shikata-s@umin.org.
authors.forename: Satoru
authors.initials: S
authors.lastname: Shikata
authors.affiliation: Department of Family Medicine, Mie Prefectural Ichishi Hospital, 616 Minamiieki, Hakunsan-cho, Tsu, Mie, 515-3133, Japan.
authors.forename: Hiromu
authors.initials: H
authors.lastname: Takeda
authors.affiliation: Department of Surgery, Flinders Medical Centre, Bedford Park, SA, 5042, Australia.
authors.forename: Lauren
authors.initials: L
authors.lastname: Dawes
authors.affiliation: General Internal Medicine, Japanese Red Cross Nagoya Daini Hospital, 2-9 Myoken-cho, Showa-ku, Nagoya, 466-8650, Aichi, Japan.
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Noguchi
authors.affiliation: Department of Health Informatics, Kyoto University School of Public Health, Konoe-cho, Yoshida, Sakyo-ku, Kyoto, 606-8501, Japan.
authors.forename: Takeo
authors.initials: T
authors.lastname: Nakayama
authors.affiliation: Department of Family Medicine, Mie University School of Medicine & Graduate School of Medicine, 2-174 Edobashi, Tsu, Mie, 514-8507, Japan.
authors.forename: Yousuke C
authors.initials: YC
authors.lastname: Takemura
mesh_terms: D018784:Abdominal Abscess / Q000453:epidemiology*; D000208:Acute Disease; D001062:Appendectomy / Q000379:methods*; D001064:Appendicitis / Q000601:surgery*; D006801:Humans; D015994:Incidence; D010535:Laparoscopy / Q000379:methods*; D007902:Length of Stay / Q000706:statistics & numerical data*; D016017:Odds Ratio; D061646:Operative Time; D011183:Postoperative Complications / Q000453:epidemiology; D016032:Randomized Controlled Trials as Topic; D013530:Surgical Wound Infection / Q000453:epidemiology*; D016896:Treatment Outcome
keywords: Cumulative meta-analysis; Laparoscopic appendectomy; Open appendectomy; Randomized controlled trials