Background:

The increasing use of monoclonal antibodies (mAb) is associated with an increase in hypersensitivity reactions (HR). The management of patients with HR to mAbs is not well established.

Objective:

Characterize the allergologic study of patients with suspected HR to this class of drugs.

Methods:

Retrospective analysis of patients referred to our drug allergy department with suspected HR to mAb (2013-2019). Diagnosis was considered confirmed by suggestive clinical history and positive skin tests/drug provocation test or reproducible reaction during desensitization, considered probable when suggestive clinical history and excluded when drug provocation test negative.

Results:

Eighteen patients were included, 56% female, median age 62 years (23;74). Culprit drugs were rituximab, cetuximab, nivolumab, trastuzumab and trastuzumab-emtansina used to treat cancer, immune thrombocytopenic purpura, systemic lupus erythematosus and idiopathic pulmonary fibrosis. All HR were immediate. Symptoms included anaphylaxis, fever, skin manifestations, tachycardia and hypertension. HR occurred in the 1st administration in 61% of the patients. Skin tests were positive in 1 patient (1/8) and drug provocation tests were all negative (12/12). Due to the severity and underlying clinical condition, desensitization was performed in 12 patients, 3 of which had a reproducible reaction during the procedure. Diagnosis was confirmed in 17% (n=3), considered probable in 17% (n=3) and excluded in 67% (n=12).

Conclusions:

Although the mechanism underlying HR is relevant, the severity of the reaction is the major determinant in the allergology study definition. In the presence of negative skin tests and/or mild reactions, drug provocation test is recommended, having excluded diagnosis in 67% of our patients, presenting as extremely important in clarifying diagnosis. In the presence of positive skin tests and/or moderate/severe reactions, the use of desensitization as first approach is recommended.

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