Which of the following is NOT a criterion of the PERC rule for ruling out pulmonary embolism?

• A. O2 sat < 95%
• B. Coughing blood
• C. Leg swelling disparity
• D. Oxygen saturation 96%

Answer: (D)

The PERC rule helps rule out pulmonary embolism in patients who are already considered low risk, using eight criteria. If all of these criteria are met, the clinician can often avoid further testing. One key point is that the criteria include an oxygen saturation of 95% or higher; anything below 95% does not meet the criterion and means PERC cannot be used to rule out PE.

Among the options, the statement about oxygen saturation below 95% is not a criterion. The rule requires oxygen saturation to be at least 95%. The other options reflect: coughing blood is hemoptysis (no hemoptysis is a criterion), leg swelling corresponds to no unilateral leg swelling (a criterion), and an oxygen saturation of 96% satisfies the criterion.