D2.18 - Evaluating the Penicillin Allergy Diagnosis Process with Real-Life Data

Penicillins remain first-line antibiotics for a wide range of bacterial infections. Adverse reactions are reported in at least 0.5% of penicillin administrations, many of which are subsequently documented as “penicillin allergy” in medical records, leading to unnecessary antibiotic restrictions. This study aimed to evaluate the diagnostic process of penicillin allergy and to investigate factors associated with reaction severity.

Patients with suspected penicillin allergy who underwent a commercial penicillin allergy test using the Drug Allergy Pathway (DAP, Diater) between 2022 and 2025 were retrospectively evaluated. Medical records were reviewed for demographic characteristics, reaction history, route of drug administration, reaction severity due to Ring & Messmer grading system and pulmonary function test results.

A total number of 51 cases with complete data were included. The mean age was 40.86 ± 13.86 years (range: 18–69), and 76.8% were female. The mean pre-DAP FEV₁ was 96.2% ± 11.97%. The mean interval between the index reaction and allergic evaluation was 162.48 ± 267.19 months. Drug exposure occurred via the oral route in 78.4% of patients, intravenously in 11.8%, intramuscularly in 5.9%, and via other routes in 3.9% (two patients reported reactions during prick testing, and one patient could not recall the route). Severity of drug reactions was most commonly grade 1 (60.8%), followed by grade 2 (17.6%) and grade 3 (15.7%). Adrenaline was administered during the index reaction in only 7.8% of patients. A history of drug allergy other than penicillin was present in 25.5% of cases. DAP testing was negative in 92.2% of patients. No statistically significant association was found between the route of drug administration and reaction severity. Oral provocation tests with aminopenicillins were safely performed in a substantial group of patients with negative DAP results.

These real-world data demonstrate that penicillin tests are able to demonstrate true penicillin allergy. This study showed that almost 80% to 90% of cases once considered allergic are ultimately able to tolerate penicillins. These findings support the use of structured diagnostic algorithms and drug provocation tests to reduce unnecessary penicillin allergy labeling. Peniciliin testing is useful resulting in the decreased need for broad-spectrum antibiotics and development of multi-drug resistant organisms.