SSI rates higher among lower volume hospitals

PHILADELPHIA — The rates of surgical site infections following total hip arthroplasty and coronary artery bypass graft surgery were higher among Medicare patients who underwent surgery in hospitals with lower surgical volume, according to data presented at IDWeek 2014.

According to Michael Calderwood, MD, MPH, of the department of population medicine at Harvard Medical School and the division of infectious diseases at Brigham and Women’s Hospital, data on health care-associated infections (HAIs) in US hospitals are publicly reported and used to compare performance across hospitals, but many hospitals are excluded from the comparisons due to low volume of device days, patient days or surgical procedures.

Michael Calderwood

Michael Calderwood

“If you look at Medicare data, currently, US hospitals report data on six HAIs, but a range of 16% to 73% are not currently ranked in this online system because their predicted number of infections is less than one,” Calderwood said during his presentation. “That doesn’t mean that they actually reported less than one infection. Many actually reported more than that, but the predictions are based on their denominator, and thus their predicted number of infections is less than one. This is also true for state report cards.”

Calderwood and colleagues reviewed 2010 Medicare Provider and Analysis Review inpatient claims data, including short-stay acute care hospitals that perform total hip arthroplasty or coronary artery bypass graft (CABG) procedures on Medicare patients. They searched claims within 90 days of the procedures for ICD-9 codes that indicated a surgical site infection (SSI) and then calculated odds of infections by Medicare surgical volume, adjusting for age, gender and coded comorbidities.

They found the rates of claims-based SSIs declined in hospitals that had a higher volume of procedures. For total hip arthroplasty in hospitals performing more than 100 procedures per year, the rate of coded SSIs was 1.9% vs. 2.9% for hospitals performing one to 24 procedures per year (OR=1.5; 95% CI, 1.3-1.7). For CABG, the rate of coded SSIs was 5% for hospitals performing 100 or more procedures per year, vs. 7% for hospitals performing one to 24 procedures (OR=1.4; 95% CI, 1.1-1.7).

There was also a higher risk for infection after total hip arthroplasty in hospitals that performed 24 to 49 or 50 to 99 procedures per year, compared with hospitals performing more than 100. For CABG, there was also a higher risk for SSIs in hospitals performing 24 to 49 procedures a year.

Calderwood said that 72% of hospitals in the United States are in the higher risk group for SSI after total hip arthroplasty (fewer than 100 procedures per year), and 28% of hospitals are in the higher risk group for SSI after CABG (fewer than 50 procedures per year).

“A large proportion of hospitals fall into these low volume, higher risk groups,” Calderwood said. “This highlights the need to identify and validate methods to compare SSI performance in hospitals performing a lower volume of procedures, rather than just ignoring these hospitals in our public reporting.” – by Emily Shafer

For more information:

Calderwood M. Abstract 111. Presented at: IDWeek 2014; Oct. 8-12; Philadelphia.

Disclosure: Calderwood reports no relevant financial disclosures.


Josh Sandberg

Josh Sandberg is the President and CEO of Ortho Spine Partners and sits on several company and industry related Boards. He also is the Creator and Editor of OrthoSpineNews.

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