title: Bayesian comparative assessment of diagnostic accuracy of low-dose CT scan and ultrasonography in the diagnosis of urolithiasis after the application of the STONE score.
abstract: OBJECTIVE
  The objective of our study was to assess the diagnostic quality of low-dose computed tomography (CT) when compared to ultrasound (US) in diagnosis of urolithiasis using STONE score as a predictor of pre-test probability and the Bayesian statistical model to calculate post-test probabilities (POST) for both diagnostic tests.
  
  
  METHODS
  STONE score was used to form risk groups to obtain pre-test probabilities. Likelihood ratios (LR) were calculated from external data for low-dose CT and US. POST were obtained using pre-test probabilities and likelihood ratios with Bayesian nomogram. Absolute (ADG) and relative (RDG) gains in diagnostic value were calculated.
  
  
  RESULTS
  Calculated +LR for US was 12 and -LR was 0.32; for CT, +LR was 19 and -LR 0.04. +LR and low STONE for US yielded POST 57% and RDG 470%; intermediate STONE POST 92% and RDG 84%; and high STONE POST 99% and RDG 10%. -LR and low STONE for US POST 3% and RDG -70%; intermediate POST 24% and RDG -52%; and high STONE POST 74% and RDG -17.7%. +LR and low STONE for CT POST 68% and RDG 580%; moderate STONE POST 95% and RDG 90%; and high STONE POST 99% and RDG 10%. -LR and low STONE for CT POST 0% and RDG -100%; intermediate POST 4% and RDG -92%; and high STONE POST 26% and RDG -71.1%. ANOVA calculations comparing CT vs US for +LR showed no statistical significance (P value = 0.9893; LR- P value = 0.5488).
  
  
  CONCLUSIONS
  Bayesian statistical analysis demonstrated slight superiority of CT scan over US on STONE score low- and moderate-risk stratified subtypes, whereas no significant advantage was seen when evaluating high-probability patients.
authors.affiliation: Universitat de Barcelona, Barcelona, Spain. lailacochon@hotmail.com.
authors.forename: Laila
authors.identifier: http://orcid.org/0000-0001-7043-040X
authors.initials: L
authors.lastname: Cochon
authors.affiliation: Miller School of Medicine, University of Miami, Miami, FL, USA.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Smith
authors.affiliation: Department of Emergency Medicine, Jackson Memorial Hospital, Miami, FL, USA.
authors.forename: Amado Alejandro
authors.initials: AA
authors.lastname: Baez
mesh_terms: D001499:Bayes Theorem; D005260:Female; D006801:Humans; D008297:Male; D011336:Probability; D011829:Radiation Dosage; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014463:Ultrasonography / Q000379:methods*; D052878:Urolithiasis / Q000000981:diagnostic imaging*
keywords: Bayesian analysis; Low-dose CT; Ultrasound; Urolithiasis