title: Comparison of US and CT on the effect on negative appendectomy and appendiceal perforation in adolescents and adults: A post-hoc analysis using propensity-score methods.
abstract: OBJECTIVE
  To retrospectively compare ultrasound (US) and CT as the preoperative first-line imaging modality in terms of negative appendectomy rate (NAR) and appendiceal perforation rate (APR) in adolescents and adults with suspected appendicitis.
  
  
  METHODS
  We included 2,030 patients in 11 sites who underwent appendectomy following US (n = 102) or CT (n = 1,928). Propensity-score (PS) adjusted and matched comparisons were conducted. Matching was performed with 1:1 and 1:3 ratios. Secondary analyses were performed by adding appendiceal perforation to PS model.
  
  
  RESULTS
  The unadjusted NAR difference between the unmatched US and CT groups (8% [8/102] versus 3.8% [73/1,928]) was 4.1 percentage points (95% confidence interval, -1.2, -9.3; p = 0.133). The PS adjusted difference was 4.1 percentage points (-1.8, -10.0; p = 0.169). The differences after 1:1 (9% [8/94] versus 5% [5/94]) and 1:3 (9% [8/94] versus 3.0% [8/271]) matching were 3 (-4, -10, p = 0.39) and 5.6 (-0.4, -11.6, p = 0.069) percentage points, respectively. The unadjusted APR difference between the unmatched US and CT groups (22% [22/102] versus 23.8% [459/1,928]) was -2.2 percentage points (-10.4, -6.0; p = 0.59). The PS-adjusted difference was -5.2 percentage points (-13.3, -2.9; p = 0.21). The differences after 1:1 (19% [18/94] versus 24% [23/94]) and 1:3 (19% [18/94] versus 20.7% [56/271]) matching were -5 (-17, -6, p = 0.38) and -1.5 (-10.8, -7.8, p = 0.75) percentage points, respectively.
  
  
  CONCLUSIONS
  The use of US instead of CT may increase NAR but does not significantly affect APR. © 2016 Wiley Periodicals, Inc. J Clin Ultrasound 44:401-410, 2016.
authors.affiliation: Division of Statistics, Medical Research Collaborating Center, Seoul National University Bundang Hospital, Gyeonggi-do, Korea.
authors.forename: Jaebong
authors.initials: J
authors.lastname: Lee
authors.affiliation: Department of Radiology, Seoul National University Bundang Hospital, Gyeonggi-do, Korea.
authors.forename: Yousun
authors.initials: Y
authors.lastname: Ko
authors.affiliation: Division of Statistics, Medical Research Collaborating Center, Seoul National University Bundang Hospital, Gyeonggi-do, Korea.
authors.forename: Soyeon
authors.initials: S
authors.lastname: Ahn
authors.affiliation: Department of Radiology, Seoul National University Bundang Hospital, Gyeonggi-do, Korea.
authors.forename: Ji Hoon
authors.initials: JH
authors.lastname: Park
authors.affiliation: Department of Clinical Epidemiology and Biostatistics, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Hwa Jung
authors.initials: HJ
authors.lastname: Kim
authors.affiliation: Department of Social and Preventive Medicine, Inha University School of Medicine, Incheon, Korea.
authors.forename: Seung-Sik
authors.initials: SS
authors.lastname: Hwang
authors.affiliation: Department of Radiology, Seoul National University Bundang Hospital, Gyeonggi-do, Korea.|Program in Biomedical Radiation Sciences, Department of Transdisciplinary Studies, Graduate School of Convergence Science and Technology, Seoul National University, Seoul, Korea.
authors.forename: Kyoung Ho
authors.initials: KH
authors.lastname: Lee
mesh_terms: D000293:Adolescent; D000328:Adult; D001062:Appendectomy / Q000706:statistics & numerical data*; D001064:Appendicitis / Q000000981:diagnostic imaging*; D001065:Appendix / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D008297:Male; D011300:Preoperative Care / Q000379:methods / Q000706:statistics & numerical data; D057216:Propensity Score; D012189:Retrospective Studies; D012422:Rupture, Spontaneous; D014057:Tomography, X-Ray Computed / Q000706:statistics & numerical data*; D014463:Ultrasonography / Q000706:statistics & numerical data*
keywords: appendectomy; diagnostic imaging; propensity score; tomography; ultrasonography; x-radiography computed