Charted Penicillin Allergy Predicts VRE

  • by North American Correspondent, MedPage Today
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BALTIMORE -- People with a medical chart warning of penicillin allergy are more likely to be among patients with vancomycin-resistant enterococcus (VRE), a researcher said here.

In a retrospective, single-institution study, just 6% of the general hospital population had a chart warning of penicillin allergy, according to Vinitha Reddy, MD, of Penn State Hershey Medical Center in Hershey, Pa.

But among patients with VRE, the rate was 24%, Reddy reported at the annual meeting of the American College of Allergy, Asthma, and Immunology.

While causation is hard to determine, Reddy told MedPage Today, the investigators think that the charted penicillin allergy might have led doctors to use other and possibly less effective antibiotics, eventually leading to VRE.

The question is: "Do they keep getting vancomycin when they shouldn't be?" she said.

The implication is, she said, that rates of VRE might fall if the antibiotic were reserved for patients with a tested penicillin allergy.

The study covered the three years from 2009 through 2011, Reddy said, during which some 369,721 patients were admitted.

Of those, 426 patients developed VRE -- mainly blood and wound infections -- and 100 of those had a charted penicillin allergy for a rate of 24%, she said.

In contrast, just 20,249 patients in the general population had a charted penicillin allergy, for a rate of 6%, she reported. The difference was significant at P<0.001.

Interestingly, other antibiotic drug allergies were also higher in the VRE group -- 143 of the 426 patients, for a rate of 33.6%.

By comparison, she reported, only 7% of the general hospital population had such an allergy (25,589 of 369,721 patients). The difference was significant at P<0.001.

There is "starting to be a consensus that patients should be more vigorously tested for penicillin allergy," commented Jay Portnoy, MD, of Children's Mercy Hospital in Kansas City, Mo.

"But traditionally allergists haven't been really aggressive about doing that," he said.

Many people who think they are allergic to penicillin base their conclusion on an early adverse event that might not have been an allergic reaction, Portnoy, who was chair of the meeting's abstract committee, told MedPage Today.

Also, he said, most people who were truly allergic in childhood have probably outgrown it.

"Most of these people," he said, " are not allergic to penicillin."

Portnoy noted that the study can't demonstrate that the charted penicillin allergy led to over-exposure to other antibiotics and therefore resistance.

Equally, he said, it could be a case of reverse causation -- the allergy is a result of multiple exposures to antibiotics, including penicillin, with VRE arising in the course of extended therapy.