Study objective: Two separate clinical decision rules, one developed in Ottawa and the other in Pittsburgh, for the use of radiography in acute knee injuries have been previously validated and published. In this study, the rules were prospectively validated and compared in a new set of patients.

Methods: A prospective, blinded, multicenter trial was conducted in the emergency departments of three urban teaching hospitals. A convenience sample of 934 patients with knee pain requiring radiographs was enrolled. A standardized data form was completed for each patient, comprising the 10 clinical variables included in the two rules. Standard knee radiographs were then taken in each patient. The rules were interpreted by the primary investigator on the basis of the data sheet and the final radiologist radiograph reading.

Results: In the 745 patients in whom the Pittsburgh rules could be applied there were 91 fractures (12.2%). The use of the Pittsburgh rule missed one fracture, yielding a sensitivity of 99% (95% confidence interval [CI], 94% to 100%); the specificity was 60% (95% CI, 56% to 64%). The Ottawa inclusion criteria were met by 750 patients, with 87 fractures (11.6%). The Ottawa rule missed three fractures, for a sensitivity of 97% (95% CI, 90% to 99%); specificity was 27% (95% CI, 23% to 30%).

Conclusion: Prospective validation and comparison found the Pittsburgh rule for knee radiographs to be more specific without loss of sensitivity compared with the Ottawa rule.

[Seaberg DC, Yealy DM, Lukens T, Auble T, Mathias S: Multicenter comparison of two clinical decision rules for the use of radiography in acute, high-risk knee injuries. Ann Emerg Med July 1998; 32:8-13.]