Penicillin Allergy: Value of Including Amoxicillin as a Determinant in Penicillin Skin Testing

Abstract

Background: Allergy to penicillins remains an important issue. Penicillin skin testing (PST) with major and minor determinants has been shown to be a highly valuable tool for identifying IgE-mediated penicillin allergy. The value of additional testing with side-chain-specific moieties from semisynthetic penicillins such as amoxicillin is not well-established in spite of the widespread use of these medications. Methods: A retrospective review of all consecutive inpatient PST results from 1995 to 2007 comprising 1,068 patients was performed in our institution on individuals with a self-reported history of beta-lactam allergy to assess the importance of including the amoxicillin determinant in a previously validated PST panel. Descriptive statistics were performed. The PST panel included penicilloyl-polylysine, penicillin G, penicilloate, penilloate and amoxicillin. Results: Of 1,068 patients, 243 (23%) had a positive skin test reaction on the PST panel. Testing with amoxicillin was positive in 30.9% of patients, the majority of whom (81%) were also positive to 1 or more standard penicillin reagents. Fourteen of the 243 positive patients (5.8%) had a positive skin test reaction only to amoxicillin. Additionally, the use of penicilloate and penilloate minor determinants in combination with penicillin G identified a greater percentage of penicillin-allergic individuals compared to using only penicillin G (22.6 vs. 6.6%), demonstrating their importance in the PST panel. Conclusions: These data indicate that the inclusion of the amoxicillin determinant appears to identify a small but important group of allergic individuals who may otherwise test negative on a PST panel.

Diagnosis of Immediate Hypersensitivity to β-Lactam Antibiotics Can Be Made Safely with Current Approaches

“…As a result of this, recent studies have shown a different pattern of IgE sensitization from that of previous studies. These studies indicated that a significant proportion of allergic patients produced amoxicillin-specific IgE, which was likely related to the high use of broad-spectrum penicillins in southern Europe [13,14,17]. …”

“…Recent studies indicated a different sensitization profile in patients with β-lactam allergy with replacement of benzylpenicillin (BP) mainly by amoxicillin which could not be detected by testing with PPL and MDM alone [13,14,15,16,17]. As a result of this, ENDA recommended the use of skin testing not only with PPL and MDM but also with culprit drugs in order to detect side chain-specific allergies [18,19].…”

Penicillin Determinants in the Diagnosis of Immediate Hypersensitivity Reactions to β-Lactams

“…As has been reported in different studies [6] , the authors also comment on the limited value of the clinical history as a predictor of ␤ -lactam allergy [1] . Accordingly, the correct diagnosis of ␤ -lactam hypersensitivity requires a well-validated panel of penicillin determinants that, in addition to benzyl penicillin and amoxicillin determinants, must also include other ␤ -lactams.…”

“…The article by Lin et al [1] provides conclusions concerning the relevance of skin test determinants of amoxicillin in subjects with hypersensitivity reactions to ␤ -lactams. The authors state that inclusion of the amoxicillin determinants identifies a group of allergic individuals who may otherwise not be diagnosed in a conventional panel.…”

“…Several studies demonstrated that the relevant part of the amoxicillin molecule was the side chain and that this contributed to the antigenic determinants. Since then, the European Academy of Al-nificance of these changes has not been fully analyzed in many countries, and the study by Lin et al [1] is therefore a useful contribution.…”