title: Prospective validation of a decision rule for the use of radiography in acute knee injuries.
abstract: OBJECTIVE
  To validate a previously derived decision rule for the use of radiography in patients with acute knee injury.
  
  
  METHODS
  Prospectively administered survey.
  
  
  METHODS
  Emergency departments of two university hospitals serving adults.
  
  
  METHODS
  Convenience sample of 1096 of 1251 eligible adults with acute knee injuries; 124 patients were examined by two physicians.
  
  
  METHODS
  Attending emergency physicians assessed each patient for standardized clinical variables and determined the need for radiography according to the decision rule. Patients who did not have radiography underwent a structured telephone interview at day 14 to determine the possibility of a fracture. The rule was assessed for ability to correctly identify the criterion standard, fracture of the knee. An attempt was made to refine the rule by means of univariate and recursive partitioning analyses.
  
  
  RESULTS
  The decision rule had a sensitivity of 1.0 (95% confidence interval [CI], 0.94 to 1.0) for identifying 63 clinically important fractures. Physicians correctly interpreted the rule in 96% of cases, and the k value for interpretation was 0.77 (95% CI, 0.65 to 0.89). The potential relative reduction in use of radiography was estimated to be 28%. The probability of fracture, if the decision rule were "negative," is estimated to be 0% (95% CI, 0% to 0.4%). Attempts to refine the rule led to a model with improved specificity but with an unacceptable loss of sensitivity.
  
  
  CONCLUSIONS
  Prospective validation has shown this decision rule to be 100% sensitive for identifying fractures of the knee, to be reliable and acceptable, and to have the potential to allow physicians to reduce the use of radiography in patients with acute knee injury.
authors.affiliation: Division of Emergency Medicine, University of Ottawa, Ontario, Canada.
authors.forename: I G
authors.initials: IG
authors.lastname: Stiell
authors.forename: G H
authors.initials: GH
authors.lastname: Greenberg
authors.forename: G A
authors.initials: GA
authors.lastname: Wells
authors.forename: I
authors.initials: I
authors.lastname: McDowell
authors.forename: A A
authors.initials: AA
authors.lastname: Cwinn
authors.forename: N A
authors.initials: NA
authors.lastname: Smith
authors.forename: T F
authors.initials: TF
authors.lastname: Cacciotti
authors.forename: M L
authors.initials: ML
authors.lastname: Sivilotti
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003661:Decision Support Techniques; D004636:Emergency Service, Hospital / Q000592:standards* / Q000706:statistics & numerical data; D005260:Female; D050723:Fractures, Bone / Q000000981:diagnostic imaging; D006785:Hospitals, University; D006801:Humans; D007718:Knee Injuries / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D009864:Ontario; D011336:Probability; D011446:Prospective Studies; D011859:Radiography / Q000706:statistics & numerical data*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity