By Kristina Rebelo
SAN DIEGO -- April 14, 2008 -- The alarming rate of up to 29% of breast surgeries resulting in surgical-site infections (SSI) may be considerably overestimated due to subjective criteria, researchers noted here at the American Society of Breast Disease (ASBD) 32nd Annual Symposium.
Currently, reported rates of SSI after breast operations are 1% to 29%. One of the criteria for SSI from the Centers for Disease Control and Prevention (CDC), however, is "physician diagnosis of suspected infection."
"When you more strictly review the patients that met the criterion that was physician diagnosis, there were a number of patients that were very 'soft calls' for infection," said Alyssa D. Throckmorton, MD, Research Fellow, Department of Surgery, Mayo Clinic, Rochester, Minnesota.
In a poster presentation on April 10, Dr. Throckmorton said that some of the women described as having an infection could have had lymphoedema in reality, which can appear similar to an infection in its early stages with a reddening of the skin, but often are treated with antibiotics to rule out infection at initial presentation.
A retrospective chart review performed by Dr. Throckmorton and colleagues included 386 patients who underwent 455 operations with methylene blue lymphatic mapping between July 2004 and June 2006. SSI was defined using the 4 standard CDC criteria: (1) purulent drainage; (2) positive aseptically collected culture; (3) opening of the incision and absence of a negative culture; and (4) physician diagnosis.
In the cohort of 386 patients, 62 patients (16.1%) experienced SSI based on CDC criteria in 65 (14.3%) breast operations; this figure included all patients treated with antibiotics. The median time before an SSI diagnosis was 9 days (range, 1-28 days) with 73.8% of diagnoses occurring within the first 2 weeks postsurgery.
The study noted that there was a wide spectrum of suspicious clinical presentations that ranged from minimal erythema to severe cellulitis.
"When patients with definite cellulitis alone but no other objective CDC criteria are [removed from the group of] patients meeting CDC SSI criteria 1 through 3, the SSI rate is almost half of the inclusive rate," the authors noted, concluding that a provider's decision to treat possible cellulitis is such a soft criterion that it may overestimate the true SSI rate.
"At this point, even if physicians think they're dealing with a case of lymphoedema, they may treat the patient with a round of antibiotics to exclude the infection diagnosis. The outcome is that the patient's chart will be coded as if they had an infection," said Dr. Throckmorton, referring to the National Surgical Quality Improvement Program, which reports on surgical outcomes including postsurgical infection.
Cultures relevant to clinical care as infections are not always caused by Staphylococcus species. Dr. Throckmorton noted that, in 40% of her cases, the infection was not a Staph species, and cephalexin may have missed the mark. She urges physicians to order cultures when material for culture is available.
"Your infection rate is highly dependent on how [the doctor] documents CDC benchmarks for infection rates," said Dr. Throckmorton. "It's not always clear."
[Presentation title: Surgical Site Infection (SSI) After Breast Surgery: Examining the Case Definition. Poster T-24]
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