The Ottawa Knee Rule and a near-perfect sensitivity rate go hand-in-hand if an institution hopes to minimize costs by using the rule, according to a team of researchers from Dallas and Atlanta.
Dr. Stefan Tigges from the Emory Clinic in Atlanta presented his group's findings at the American Roentgen Ray Society meeting on May 11. They looked at whether adoption of the Ottawa Knee Rule would decrease the cost of evaluating adults with blunt knee trauma.
The Ottawa Knee Rule was designed by Canadian clinicians to determine whether a knee injury requires an x-ray. According to the rule, x-rays for knee injury patients are required if they present with any of the following criteria:
- Over 55 years of age
- Isolated tenderness of the patella
- Tenderness at the head of the fibula
- Inability to flex to a 90-degree angle
- Inability to bear weight over the course of four steps
Using a two-arm decision tree -- one in which the Ottawa Knee Rule was always used and one in which it was never used -- the group estimated costs based on Medicare reimbursement rates, hospital charges and U.S. Department of Labor Statistics.
For example, the Medicare reimbursement rate is $29.01 for a knee radiograph, Tigges said, while the hospital may charge up to $145 for the x-ray. According to labor statistics, the hourly wages paid to the person conducting the exam would be $13.09 per hour, while the hospital's take would be $29.27.
According to their baseline analysis, using the Ottawa Knee Rule resulted in an average savings of $3 per patient at the Medicare reimbursement rate of $29.01. When the cost was tabulated based on a hospital fee of $145, the savings came in at $17 per patient.
But in order to reduce costs significantly, the sensitivity for the Ottawa Knee Rule would have to be no less than 96%, Tigges said. In their model, if the sensitivity of the rule dropped below 96%, costs could increase by $42, particularly if the patient had to return to the emergency department for additional treatment.
The Ottawa Knee Rule would be most effective with an x-ray charge of $145 and a rule sensitivity of 99%, resulting in savings of $35. The worst-case scenario would involve a $29.01 reimbursement for the x-ray and sensitivity of 87%, resulting in a $26 loss, Tigges said.
"Using the Ottawa Knee Rule will probably result in modest cost savings," Tigges concluded. "The savings will depend on the sensitivity of the rule and the price of radiography." Other factors that may influence the success of the rule is whether emergency physicians and radiology residents are properly trained in this technique and whether they use it, Tigges added.
Other groups have reported similar numbers when applying the rule. Epidemiologists at the Loeb Health Research Institute in Ottawa also conducted a cost-savings analysis and found a mean cost savings of between $31 and $34 per patient when the Ottawa Knee Rule was used to assess adults with blunt trauma (Ann Emerg Med, Oct.1999, Vol. 34:4, pp. 438-447).
Another study from the University of Ottawa assessed the impact of the rule on clinical practice at four hospitals. During a one-year period, 3,907 patients with acute injuries were seen by staff trained to use the Ottawa Knee Rule. Patients who were discharged without undergoing an x-ray spent 85 minutes in the emergency room, and incurred a total medical charge of $80. Those who were not evaluated with the rule were in the emergency department for 118 minutes and racked up a $183 bill, the study reported (JAMA, Dec.1997, Vol.278:23, pp.2075-2079).
By Shalmali Pal
AuntMinnie.com staff writer
May 15, 2000
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