1546 Flow cytometry as a tool for delayed drug allergy reactions diagnosis: Our experience

Wednesday, 8 December 2010


The lymphocyte transformation test (LTT) is the only test to detect a sensitization of T cells to drugs in the peripheral blood of drug-allergic patients, but it is often considered more of a research than a diagnostic tool. In a pilot study, Pichler et al. evaluated surface molecule CD69 expression as a marker of T-cell activation in a group of patients with T-cell-mediated drug allergic reactions. CD69 was detectable after 48 hrs by flow cytometry in all patients tested.

Aim of the study.

We analysed 11 clinical cases of adverse drug reactions we observed in our department of allergy. In all cases clinical patterns and the time of reaction indicated a delayed type of immune mechanism.

The patients underwent clinical evaluation, skin tests for the suspected drug and CD69 analysis with flow cytometry.


Clinical evaluation was made by allergy specialist doctor in agreement with the questionnaire of EAACI interest group on drug hypersensitivity. 8 patients experienced maculo-papular rush or generalized urticaria after amoxicillin intake, 1 patient after levofloxacin and 2 patients after ibuprofen or ketoprofen administration

Skin test were performed as described by Torres MJ et al. (1).

CD69 analysis were performed with flow cytometry by using monoclonal antibodies anti CD3, CD4, CD69, as described from Pichler et al. (2) and results were expressed as S.I. (Stimulation Index).


In the group of 8 patients with delayed adverse reactions after amoxicillin intake, 3 patients showed positive intradermal skin tests with the drug, while 5 patients were negative. CD69 analisys was positive in 6 of the 8 patients.

The patient with maculo-papular rush after levofloxacine intake showed positive patch tests and positive CD69 analisys.

The 2 patients with adverse reactions to NSAIDs showed negative patch tests, but positive CD69 analisys.


On the basis of our clinical experience, CD69 measurement seems to be a promising tool to detect drug-reactive T cells in the peripheral blood of drug allergic patients.


(1) M.J. Torres , M. Blanca, J. Fernandez , A. Romano, A. Weck, W. Aberer , et al. Diagnosis of immediate allergic reactions to beta-lactam antibiotics. Allergy. 2003: 58(10):961-72.

(2) A. Beeler, L. Zaccaria,T. Kawabata, B.O. Gerber, W.J. Pichler CD69 upregulation on T cells as an in vitro marker for delayed-type drug hypersensitivity. Allergy 2008: 63: 181188