Penicillin allergy: prevalence of vague history in skin test-positive patients

Objective: Penicillin (PCN) skin testing is a reliable tool for predicting which patients can safely receive the antibiotic. Depending on the study, 7% to 76% of patients who have a history of PCN allergy have positive PCN skin tests. Many physicians approach patients who have a vague history of PCN allergy less cautiously than they approach those who have a convincing history suggestive of an IgE-mediated reaction. We reviewed the published literature to determine how many patients who had a history of PCN allergy and who were skin test-positive had a vague history of allergy. Data Sources: By cross-referencing the keywords "penicillin" and "skin test," an Ovid MEDLINE search for English language studies published from 1966 to 1998 was performed. Study Selection: Studies in which history positive/skin test-positive patients were identified, and which contained documentation of the type of previous reaction in these patients, were included in the analysis. The MEDLINE search revealed 295 English language articles, of which 27 fulfilled the inclusion criteria. Three additional studies published prior to 1966 (and therefore not available through MEDLINE) also were found, bringing the total to 30. A "convincing" history was defined to be one likely to be IgE-mediated (such as anaphylaxis, urticaria, angioedema or pruritic rash). A "vague" history was one unlikely to be IgE-mediated (such as maculopapular rash, GI symptoms, or an unknown reaction). Results: Overall, 347/1063, or 33%, of history positive/skin test-positive patients had a vague PCN allergy history, with a range of 0% to 70% among the 30 studies. Conclusion: A large proportion of patients who have PCN-specific IgE antibodies, as determined by skin testing, have vague PCN allergy histories. These results therefore, indicate that, like patients with convincing histories, patients with vague allergic histories should undergo PCN skin testing prior to PCN administration.