SAN DIEGO – During 20 months of follow-up, the diagnosis of penicillin "allergy" in hospitalized patients was associated with 10% more total hospital days and a spike in Clostridium difficile and other infections, a large 3-year study demonstrated.
"Based on other work, penicillin ‘allergy’ is inaccurate about 95% of the time," Dr. Eric M. Macy said in an interview prior to the annual meeting of the American Academy of Allergy, Asthma, and Immunology, where the work was presented. "More penicillin allergy testing of hospitalized individuals with a history of penicillin ‘allergy’ to document true penicillin allergy has the potential to reduce hospital days and serious infection prevalence," he said.
Dr. Eric Macy
In an effort to determine hospital utilization and prevalence rates of Clostridium difficile, methicillin resistant Staphylococcus aureus (MRSA), and vancomycin-resistant enterococci (VRE) in patients with and without penicillin allergy, the researchers conducted a retrospective, matched cohort study of 51,807 individuals admitted to Kaiser Foundation hospitals in Southern California during 2010-2012 out of about 3.2 million health plan members, a sample that represents about 1% of the United States population.
Dr. Macy and his associates matched 51,582 of the individuals (99.6% of all cases) to two unique control subjects without an active penicillin allergy. Cases and controls were matched by category for discharge diagnosis, sex, age, and date of admission.
Over the 3-year study period, the penicillin allergic cases averaged 0.59 (9.9%) more total hospital days during 20 months of follow-up, compared with controls. Cases were treated with significantly more fluoroquinolones, clindamycin, and vancomycin, compared with controls (P less than .0001), and cases had 30.1% more VRE infections, 23.4% more C. diff. infections, and 14.1% more MRSA than expected, compared with controls, reported Dr. Macy of the Southern California Permanente Medical Group, San Diego.
When the researchers controlled for the number of drug allergies, differences between cases and controls disappeared. Overall, Dr. Macy and his associates observed a strong positive correlation for all four outcome variables and increasing drug allergy number in both cases and controls.
"This is the largest study ever done looking at the influence of a history of penicillin allergy, hospital utilization, and serious infection prevalence," Dr. Macy remarked. "This type of study could not be done any better." Full findings appear in the March 2014 issue of the Journal of Allergy and Clinical Immunology.
The study was supported by the Kaiser Permanente Health Care Program and by ALK-Abelló, a Danish company that sells an essential penicillin skin test reagent called Pre-Pen. Dr. Macy said that he had no relevant financial conflicts to disclose.