Cardiovascular Health

Vascular Surgery Quality and Outcomes

At Stanford Health Care, we measure the likelihood for stroke in the hospital (O/E ratio), after a patient has had an elective carotid endarterectomy (CEA). CEA is a procedure used to remove plaque from the carotid artery and reduce the risk of stroke.

From January 2012 to January 2014, none of our patients who had an elective CEA had a stroke.

How is the O/E ratio calculated?

The O/E ratio comes from dividing the observed rate at a hospital by the expected rate, as calculated by the Society of Vascular Surgery (SVS) Vascular Quality Initiative (VQI), to get a risk-adjusted ratio:

• Observed rate: The actual number of patients that had an event (like a stroke) in the hospital.
• Expected rate: The predicted number of patients to have that event in the hospital. This is calculated after risk adjustment to "level the playing field."

How to read the O/E ratio

• O/E ratio > 1.0: The outcomes are worse than expected, because more people had an event than expected.
  
• O/E ratio = 1.0: The outcomes are the same as expected when the observed rate equals the expected rate. The number of people who actually had an event was the same as expected.
  
• O/E ratio < 1.0: The outcomes are better than expected, because fewer people had an event than expected.

The VQI calculates data from more than 300 hospitals. This data is risk-adjusted, meaning that each patient's medical history, risk factors, and surgery type are recorded and analyzed the same way across the country to create the overall risk-adjusted O/E ratio.