title: Derivation of decision rules to predict clinically important outcomes in acute flank pain patients.
abstract: OBJECTIVE
  Routine CT for patients with acute flank pain has not been shown to improve patient outcomes, and it may unnecessarily expose patients to radiation and increased costs. As preliminary steps toward the development of a guideline for selective CT, we sought to determine the prevalence of clinically important outcomes in patients with acute flank pain and derive preliminary decision rules.
  
  
  METHODS
  We analyzed data from a randomized trial of CT vs. ultrasonography for patients with acute flank pain from 15 EDs between October 2011 and February 2013. Clinically important outcomes were defined as inpatient admission for ureteral stones and alternative diagnoses. Clinically important stones were defined as stones requiring urologic intervention. We sought to derive highly sensitive decision rules for both outcomes.
  
  
  RESULTS
  Of 2759 participants, 236 (8.6%) had a clinically important outcome and 143 (5.2%) had a clinically important stone. A CDR including anemia (hemoglobin <13.2g/dl), WBC count >11000/μl, age>42years, and the absence of CVAT had a sensitivity of 97.9% (95% CI 94.8-99.2%) and specificity of 18.7% (95% 17.2-20.2%) for clinically important outcome. A CDR including hydronephrosis, prior history of stone, and WBC count <8300/μl had a sensitivity of 98.6% (95% CI 94.5-99.7%) and specificity of 26.0% (95% 24.2-27.7%) for clinically important stone.
  
  
  CONCLUSIONS
  We determined the prevalence of clinically important outcomes in patients with acute flank pain, and derived preliminary high sensitivity CDRs that predict them. Validation of CDRs with similar test characteristics would require prospective enrollment of 2100 patients.
authors.affiliation: Department of Emergency Medicine, University of California, San Francisco, San Francisco, CA, USA. Electronic address: ralph.wang@ucsf.edu.
authors.forename: Ralph C
authors.initials: RC
authors.lastname: Wang
authors.affiliation: Department of Emergency Medicine, University of California, San Francisco, San Francisco, CA, USA.
authors.forename: Robert M
authors.initials: RM
authors.lastname: Rodriguez
authors.affiliation: Department of Emergency Medicine, University of California, San Francisco, San Francisco, CA, USA.
authors.forename: Jahan
authors.initials: J
authors.lastname: Fahimi
authors.affiliation: Division of Emergency Medicine, University of Washington, Seattle, WA, USA.
authors.forename: M Kennedy
authors.initials: MK
authors.lastname: Hall
authors.affiliation: Department of Epidemiology and Biostatistics, University of California, San Francisco, CA, USA.
authors.forename: Stephen
authors.initials: S
authors.lastname: Shiboski
authors.affiliation: Department of Urology, University of California, San Francisco, San Francisco, CA, USA.
authors.forename: Tom
authors.initials: T
authors.lastname: Chi
authors.affiliation: Department of Epidemiology and Biostatistics, University of California, San Francisco, CA, USA; Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, USA.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Smith-Bindman
mesh_terms: D059787:Acute Pain / Q000209:etiology*; D000328:Adult; D000740:Anemia / Q000150:complications; D001064:Appendicitis / Q000150:complications / Q000175:diagnosis / Q000000981:diagnostic imaging; D003092:Colitis / Q000150:complications / Q000175:diagnosis / Q000000981:diagnostic imaging; D003661:Decision Support Techniques; D004239:Diverticulitis, Colonic / Q000150:complications / Q000175:diagnosis / Q000000981:diagnostic imaging; D005260:Female; D021501:Flank Pain / Q000209:etiology*; D006801:Humans; D006869:Hydronephrosis / Q000150:complications; D007958:Leukocyte Count; D008297:Male; D008875:Middle Aged; D010808:Physical Examination; D011704:Pyelonephritis / Q000150:complications / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000652:urine; D016032:Randomized Controlled Trials as Topic; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed; D014463:Ultrasonography; D014514:Ureteral Calculi / Q000150:complications* / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000652:urine; D016482:Urinalysis; D014552:Urinary Tract Infections / Q000150:complications / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000652:urine; D052878:Urolithiasis / Q000150:complications / Q000175:diagnosis / Q000000981:diagnostic imaging / Q000652:urine