The purpose of PEDAL is to develop better diagnostic tools for the investigation of patients with alleged allergy to penicillin.
Methods:
A total of 405 patients suspected of having penicillin allergy were evaluated at the Allergy Centre, Odense University Hospital, Denmark according to ENDA guidelines proposed for diagnosing penicillin allergy. The ENDA guidelines were extended, including a prolonged oral (one week) treatment (p.o.7) with penicillin. P.o.7 was given to all patients with a negative outcome in the ENDA program.
Results:
Forty-four of the 405 patients were IgE sensitized to penicillin and one reacted in the standard prick test (SPT). Intracutaneous testing (ICT) was subsequently performed in patients with negative IgE and SPT and another 20 patients were positive in ICT. The remaining 340 patients were challenged with penicillin according to ENDA guidelines.
Five patients were positive on the titrated intravenous challenge, the remaining 335 received oral provocation (single dose) with phenoxymethylpenicillin, where 15 had positive reactions. The remaining 320 patients received p.o.7 and here 13 patients responded with positive outcome.
Among the 307 patients with a negative outcome 88 had a case history of reaction to other β-lactam antibiotics and they were subsequently tested with the culprit drug. 13 patients had a positive outcome – 3 patients on single dose provocation and another 10 during p.o.7.
In all, the extended penicillin diagnostic work up was positive in 111 patients (27.4%). 88 of the 405 patients (30.0%) showed immediate reactions according to ENDA guidelines and additionally 23 patients (5.7%) reacted during p.o.7.
Conclusions:
We have demonstrated that approximately 20% of all the patients with positive outcome on penicillin challenge are found by adding prolonged oral (one week) treatment (p.o.7) with penicillins. The current ENDA guidelines do not take this finding into account.