title: Measurement error in CT assessment of appendix diameter.
abstract: BACKGROUND
  Appendiceal diameter continues to be cited as an important criterion for diagnosis of appendicitis by computed tomography (CT).
  
  
  OBJECTIVE
  To assess sources of error and variability in appendiceal diameter measurements by CT.
  
  
  METHODS
  In this institutional review board-approved review of imaging and medical records, we reviewed CTs performed in children <18 years of age between Jan. 1 and Dec. 31, 2010. Appendiceal diameter was measured in the axial and coronal planes by two reviewers (R1, R2). One year later, 10% of cases were remeasured. For patients who had multiple CTs, serial measurements were made to assess within patient variability. Measurement differences between planes, within and between reviewers, within patients and between CT and pathological measurements were assessed using correlation coefficients and paired t-tests.
  
  
  RESULTS
  Six hundred thirty-one CTs performed in 519 patients (mean age: 10.9 ± 4.9 years, 50.8% female) were reviewed. Axial and coronal measurements were strongly correlated (r = 0.92-0.94, P < 0.0001) with coronal plane measurements significantly larger (P < 0.0001). Measurements were strongly correlated between reviewers (r = 0.89-0.9, P < 0.0001) but differed significantly in both planes (axial: +0.2 mm, P=0.003; coronal: +0.1 mm, P=0.007). Repeat measurements were significantly different for one reviewer only in the axial plane (0.3 mm difference, P<0.05). Within patients imaged multiple times, measured appendix diameters differed significantly in the axial plane for both reviewers (R1: 0.5 mm, P = 0.031; R2: 0.7 mm, P = 0.022).
  
  
  CONCLUSIONS
  Multiple potential sources of measurement error raise concern about the use of rigid diameter cutoffs for the diagnosis of acute appendicitis by CT.
authors: Department of Radiology, MLC 5031, Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., Cincinnati, OH, 45229, USA. andrew.trout@cchmc.org.
authors: Andrew T
authors: AT
authors: Trout
authors: Department of Biostatistics and Epidemiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.
authors: Bin
authors: B
authors: Zhang
authors: Department of Radiology, MLC 5031, Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., Cincinnati, OH, 45229, USA.
authors: Alexander J
authors: AJ
authors: Towbin
mesh_terms: D000293:Adolescent; D001064:Appendicitis / Q000000981:diagnostic imaging* / Q000473:pathology*; D001065:Appendix / Q000000981:diagnostic imaging* / Q000473:pathology*; D002648:Child; D003951:Diagnostic Errors; D005260:Female; D006801:Humans; D008297:Male; D011857:Radiographic Image Interpretation, Computer-Assisted; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: Appendicitis; Appendix; Children; Computed tomography; Measurement