Triage nurse application of the Ottawa knee rule

Objective: To determine interobserver agreement; between triage registered nurses (RNs) and emergency physicians (EPs) regarding indication for knee radiographs by applying the Ottawa knee rule (OKR) and individual components of the rule. Methods: This was a prospective, observational study in a suburban, teaching emergency department. The study enrolled a convenience sample of patients aged >17 years with traumatic knee injuries less than one week old. Patients with prior knee surgery or distracting conditions were excluded. Before study initiation, the RNs and EPs were in-serviced in the OKR. Nurses and EPs independently examined each patient for OKR criteria, blinded to the other's assessment. Knee radiographs were ordered at the discretion of the EP and were interpreted by board-certified radiologists. All patients received follow-up with a structured telephone interview to identify any undetected fractures. Kappa was calculated for each component and the overall application of the OKR to assess interobserver agreement. Results: Ninety-six patients were enrolled. The mean age was 39.6 +/- 18.7 years; 50% were male. Eight patients (8%) had knee fractures. Interobserver agreements between the RNs and EPs for individual components of the OKR were: age greater than or equal to 55 years (kappa = 0.97); inability to weight bear (kappa = 0.51); inability to bend knee to 90 degrees (kappa = 0.52); fibular head tenderness (kappa = 0.45); and isolated patellar tenderness (kappa = 0.40). The EPs and RNs agreed with OKR criteria for x-ray 71% of the time (kappa = 0.41). Conclusions: The only criterion that resulted in almost perfect agreement between the RNs and EPs was patient age; agreement for the other four criteria and the overall decision to order x-rays was moderate.