title: Derivation and validation of a clinical prediction rule for uncomplicated ureteral stone--the STONE score: retrospective and prospective observational cohort studies.
abstract: OBJECTIVE
  To derive and validate an objective clinical prediction rule for the presence of uncomplicated ureteral stones in patients eligible for computed tomography (CT). We hypothesized that patients with a high probability of ureteral stones would have a low probability of acutely important alternative findings.
  
  
  METHODS
  Retrospective observational derivation cohort; prospective observational validation cohort.
  
  
  METHODS
  Urban tertiary care emergency department and suburban freestanding community emergency department.
  
  
  METHODS
  Adults undergoing non-contrast CT for suspected uncomplicated kidney stone. The derivation cohort comprised a random selection of patients undergoing CT between April 2005 and November 2010 (1040 patients); the validation cohort included consecutive prospectively enrolled patients from May 2011 to January 2013 (491 patients).
  
  
  METHODS
  In the derivation phase a priori factors potentially related to symptomatic ureteral stone were derived from the medical record blinded to the dictated CT report, which was separately categorized by diagnosis. Multivariate logistic regression was used to determine the top five factors associated with ureteral stone and these were assigned integer points to create a scoring system that was stratified into low, moderate, and high probability of ureteral stone. In the prospective phase this score was observationally derived blinded to CT results and compared with the prevalence of ureteral stone and important alternative causes of symptoms.
  
  
  RESULTS
  The derivation sample included 1040 records, with five factors found to be most predictive of ureteral stone: male sex, short duration of pain, non-black race, presence of nausea or vomiting, and microscopic hematuria, yielding a score of 0-13 (the STONE score). Prospective validation was performed on 491 participants. In the derivation and validation cohorts ureteral stone was present in, respectively, 8.3% and 9.2% of the low probability (score 0-5) group, 51.6% and 51.3% of the moderate probability (score 6-9) group, and 89.6% and 88.6% of the high probability (score 10-13) group. In the high score group, acutely important alternative findings were present in 0.3% of the derivation cohort and 1.6% of the validation cohort.
  
  
  CONCLUSIONS
  The STONE score reliably predicts the presence of uncomplicated ureteral stone and lower likelihood of acutely important alternative findings. Incorporation in future investigations may help to limit exposure to radiation and over-utilization of imaging.
  
  
  BACKGROUND
  www.clinicaltrials.gov NCT01352676.
authors.affiliation: Department of Emergency Medicine, Yale University School of Medicine, New Haven, CT, USA.
authors.forename: Christopher L
authors.initials: CL
authors.lastname: Moore
authors.forename: Scott
authors.initials: S
authors.lastname: Bomann
authors.forename: Brock
authors.initials: B
authors.lastname: Daniels
authors.forename: Seth
authors.initials: S
authors.lastname: Luty
authors.forename: Annette
authors.initials: A
authors.lastname: Molinaro
authors.forename: Dinesh
authors.initials: D
authors.lastname: Singh
authors.forename: Cary P
authors.initials: CP
authors.lastname: Gross
mesh_terms: D000328:Adult; D003661:Decision Support Techniques; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D064887:Observational Studies as Topic; D011446:Prospective Studies; D015203:Reproducibility of Results; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed; D014514:Ureteral Calculi / Q000175:diagnosis* / Q000000981:diagnostic imaging