Use of commercial anti-penicillin IgE fluorometric enzyme immunoassays to diagnose penicillin allergy.

BACKGROUND The intermittent unavailability of penicilloyl-polylysine since September 2000 has focused interest on commercial anti-penicillin IgE fluorometric enzyme immunoassay (FEIA) tests to evaluate penicillin allergy. There has been no published comparison of commercial anti-penicillin IgE FEIAs and penicillin skin testing performed in the United States. OBJECTIVE To determine whether the current commercial anti-penicillin IgE FEIAs can replace or augment penicillin skin testing and oral challenges when evaluating individuals with a history of penicillin allergy for future therapeutic penicillin tolerance. METHODS A prospective convenience sample of 150 individuals with a history of penicillin allergy were evaluated between January 23, 2007, and August 4, 2009, with both penicillin skin tests and commercial anti-penicillin IgE FEIAs to penicillin G, penicillin V, and amoxicillin. All individuals with a negative penicillin skin test result underwent oral penicillin class antibiotic challenges. All individuals with a positive anti-penicillin IgE FEIA result also underwent oral penicillin class antibiotic challenges. RESULTS Six individuals (4.0%; 95% confidence interval [CI], 0.9% to 7.1%) had positive penicillin skin test results, and none had positive FEIA results. Four individuals (2.7%; 95% CI, 0.1% to 5.3%) had positive FEIA results, and none had positive penicillin skin test results. Three individuals (2.0%; 95% CI, -0.2% to 4.2%) had positive oral challenge results, 1 with hives at 6 hours after challenge and 2 with delayed-onset (at >24 hours) nonurticarial rashes, and none had positive FEIA results. CONCLUSIONS The current commercial anti-penicillin IgE FEIAs are not useful in diagnosing penicillin allergy in patients with remote histories of penicillin allergy. Penicillin skin testing and, if the results are negative, an oral challenge remain the criterion standard tests to determine therapeutic penicillin tolerance.