Study Finds Publicly Reported Hospital Quality Rankings for Blood Clot Rates May Mislead Patients

Oct 07, 2013, 16:30 ET from Northwestern Memorial Hospital

Northwestern Medicine study suggests postoperative blood clot rate measure is flawed

CHICAGO, Oct. 7, 2013 /PRNewswire-USNewswire/ -- A study published today in JAMA by Northwestern Medicine® researchers suggests that a publicly reported outcomes quality measure, meant to reflect a hospital's success in preventing blood clots following a surgery, is fundamentally flawed. The measure, known as PSI-12 VTE, was designed to measure the rates of patients with postoperative venous thromboembolism (VTE), which occurs when a potentially preventable blood clot develops following a patient's surgery. Such blood clots can cause serious or even fatal complications for patients.

The study, "Evaluation of Surveillance Bias and the Validity of the Venous Thromboembolism Quality Measure," found the validity of the quality measure questionable because it scores hospitals based on the rates of patients with postoperative venous thromboembolism (VTE or intravenous blood clot) they report, regardless of how proactive their clinicians are in VTE testing and prevention. The authors argue that the measure doesn't accurately reflect the quality of care provided because it contains a surveillance bias where hospitals that are more vigilant in performing VTE testing will likely find more instances of postoperative VTE, resulting in what appears to be a higher rate of blood clots and a worse hospital ranking.

"It is very possible that patients are being misled by this measure when they look at publicly available rankings," said Karl Y. Bilimoria, MD, MS, surgical oncologist at Northwestern Memorial Hospital, director of the Surgical Outcomes and Quality Improvement Center at Northwestern University Feinberg School of Medicine and lead author for the study. "Our results indicate that patients who review hospital rankings or quality reports that use this VTE rate measure may actually be guided away from hospitals with higher levels of safety and quality care, toward lower quality hospitals."

To assess the impact of the surveillance bias on the validity of using reported VTE rates as a quality measure, researchers compiled performance results from approximately 2,800 hospitals using 2010 Hospital Compare, American Hospital Association, and Medicare claims data for 954,926 surgical patient discharges following major surgery. VTE imaging and VTE event rates were calculated for each hospital. A summary score of characteristics reflecting a hospital that provides a higher quality of care – such as a hospital's number of accreditations, inpatient beds and quality initiatives – was then applied to each hospital in the study.

Northwestern researchers found that hospitals with high rates for implementing VTE preventions also surprisingly had high VTE event rates. The study also revealed that hospitals with more characteristics reflecting a higher quality of care unexpectedly had higher VTE event rates. "Most importantly," the authors write, "hospital VTE rates were associated with the intensity of detecting VTE with imaging studies." Hospitals that performed fewer tests to look for blood clots (those in the lowest imaging rate quartile) diagnosed 5 VTEs per 1,000 patients, but hospitals in the highest imaging rate quartile found more than double that amount with 13.5 VTEs per 1,000 patients.

"The more you look for something the more you will find. Therefore, under the appropriate clinical circumstances, evaluating patients for VTE is indicative of high quality care," said Gary A. Noskin, MD, senior vice president and chief medical officer at Northwestern Memorial and professor of medicine at the Feinberg School. "Hospitals like Northwestern Memorial that do an excellent job of identifying VTE to ensure patients receive the best treatment should be recognized for thorough care."

"Although our study suggests that the blood clots after surgery measure does not measure VTE rates accurately, we need to continue measuring the hospitals' quality of care for the prevention of blood clots after surgery," said Bilimoria. "Our team is currently developing some novel approaches to solve this problem."

"Evaluation of Surveillance Bias and the Validity of the Venous Thromboembolism Quality Measure," is currently available on JAMA's website and will appear in the October 9, 2013 print edition of JAMA.

About Northwestern Memorial HealthCare
Northwestern Memorial HealthCare is the parent corporation of Chicago's Northwestern Memorial Hospital, an 894-bed academic medical center hospital and Northwestern Lake Forest Hospital, a 201-bed community hospital located in Lake Forest, Illinois. 

About Northwestern Memorial Hospital
Northwestern Memorial is one of the country's premier academic medical center hospitals and is the primary teaching hospital of the Northwestern University Feinberg School of Medicine.  Along with its Prentice Women's Hospital and Stone Institute of Psychiatry, the hospital has 1,705 affiliated physicians and 6,769 employees.  Northwestern Memorial is recognized for providing exemplary patient care and state-of-the art advancements in the areas of cardiovascular care; women's health; oncology; neurology and neurosurgery; solid organ and soft tissue transplants and orthopaedics.

Northwestern Memorial has nursing Magnet Status, the nation's highest recognition for patient care and nursing excellence. Northwestern Memorial ranks 6th in the nation in the U.S. News & World Report 2013-14 Honor Roll of America's Best Hospitals. The hospital is recognized in 14 of 16 clinical specialties rated by U.S. News and is No. 1 in Illinois and Chicago in U.S. News' 2013-14 state and metro rankings, respectively. For 13 years running, Northwestern Memorial has been rated among the "100 Best Companies for Working Mothers" guide by Working Mother magazine. The hospital is a recipient of the prestigious National Quality Health Care Award and has been chosen by Chicagoans as the Consumer Choice according to the National Research Corporation's annual survey for 13 years. 

SOURCE Northwestern Memorial Hospital