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Variance in definitions for surgical wound infection can cause rates to fluctuate
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SAN DIEGO — The use of a single definition for surgical wound infection can influence changes in wound infection rates over time at a single center, according to a study presented here at the 2011 Annual Meeting of the American Academy of Orthopaedic Surgeons.
“The definition of surgical wound infection, there is a misconception that it is easy. However, it is very difficult to actually define it,” Mohamed Sukeik, MD, said during his presentation. “The five cardinal signs of infection are unreliable and not reproducible.”
Sukeik and his colleagues assessed agreement among three common definitions of surgical wound infection as a performance indicator in total knee arthroplasty: the Centers for Disease Control (CDC) 1992 definition, the Nosocomial Infection National Surveillance Service (NINSS) modification of the CDC definition and the ASEPSIS scoring method.
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Findings
The investigators performed a prospective study of 500 surgical wounds in 482 patients who underwent knee arthroplasties at a single tertiary center between May of 2002 and December of 2004. The wounds were assessed according to the different definitions of surgical wound infection.
According to the study, the most commonly isolated species were Coagulase negative staphylococci (33.3%), Staphylococcus aureus (25%) and Pseudomonas aeruginosa (16.6%).
The group found the mean percentage of wounds classified as infected differed “substantially” with different definitions: 5.8% with the CDC definition, 3.6% with the NINSS definition and 2.2% with an ASEPSIS score greater than 20.
With the inclusion of superficial infections, Sukeik said, 5.2% (26) of all observed wounds received conflicting diagnoses. He added that 1.4% of these were classified as infected by both the ASEPSIS and CDC definitions. Excluding superficial infections enabled the definitions to estimate “about the same” overall percentage of infection (2.2% and 2.6% in the ASEPSIS and CDC definitions, respectively), but Sukeik noted there were nearly three times as many conflicting infection diagnoses as concordant ones.
“If you take out the superficial wound infections according to the CDC system, you find that the level of agreement has increased to 97.2%. But again, you would not notice that the disconcordance is quite significant in relation to the amount which has been diagnosed as infected by both definitions,” Sukeik said.
Single definition, single center
According to the findings, the various distinctions among surgical wound infection definitions contribute significantly to how infections are classified after knee arthroplasty. Small changes in the CDC definition, it was noted, caused “major variation” in the estimated percentages of wound infection.
“We say that it is not a wise thing to compare these surgical wound infection definitions,” Sukeik concluded. “Rather, it would be much wiser to use a single definition. Considering at a single center over a period of time, it may give us more information about surgical wound infections and reporting them.”
Reference:
- Sukeik M, et al. Surgical wound infections in total knee replacement: A comparison of common definitions. Paper 127. Presented at the 2011 Annual Meeting of the American Academy of Orthopaedic Surgeons. Feb. 15-19, 2011. San Diego.
Disclosure: Sukeik has no relevant financial disclosures.
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