Risk assessment of immediate systemic reactions from skin tests with β-lactam antibiotics.

BACKGROUND

Some clinical studies have demonstrated that skin tests for β-lactam antibiotics may cause more adverse reactions than skin tests for common allergens.

OBJECTIVE

To assess the risk of systemic reactions from penicillin skin testing, based on a pre-test categorization of patients, in order to establish an appropriate strategy for preempting and dealing with cases.

METHODS

A case series of 175 patients with a suspected allergy to penicillin was reviewed, and patients were classified as having a low or high probability of allergic sensitization to penicillin, according to their clinical history. For every group, the rate and the increase in the relative risk (RRI) of systemic reactions by skin testing were calculated. The results were compared to those reported in the available literature.

RESULTS

In our case series of 175 patients, 52 were classified as having a high probability of being allergic to penicillin, according to their clinical history. Five systemic reactions to skin testing were observed, and these were exclusively in this group (9.61%, RRI = 479). In agreement with the literature, patients with a high likelihood of penicillin allergy showed an increase of up to 10% in the occurrence of systemic reactions at skin testing; in patients who had had severe allergic reactions, this figure was up to 20%.

CONCLUSIONS

The RRI of systemic reactions by skin testing is proportional to the pre-test probability of a true immediate hypersensitivity reaction to β-lactam antibiotics. In the present case series, only patients with high pre-test probability were at risk, and this group should therefore be skin tested and monitored in a hospitalization regimen, where resuscitation staff and access to an emergency room are immediately available.