Letter to the editor

Selective allergic reactions to clavulanic acid: A report of 9 cases

Despite their low frequency, drug hypersensitivity reactions (DHRs) can be serious and result in lifelong sequelae. The diagnosis is critical to avert future reactions and should identify the culprit drug or drugs and safe alternatives. However, making the diagnosis can be complex and challenging. Reliable in vitro tests can offer the potential to improve a diagnosis of DHR and influence medical decision making. Importantly, in vitro testing is frequently not performed as a test in isolation but rather as a component of a diagnostic algorithm along with additional tests. There are several in vitro approaches for the different endotypes of DHRs. However, only few are available for routine diagnosis, and many are restricted to research laboratories. In vitro tests exhibit varying sensitivity and specificity depending on the drug involved and the clinical phenotype. In vitro tests can complement skin tests, especially in patients with negative or equivocal skin test responses inconsistent with the clinical presentation and in severe reactions in which drug provocation tests are contraindicated. The main unmet need for many in vitro tests for the diagnosis of DHRs is validation in larger studies with standardized controls that could harmonize diagnostic management between the United States, European Union, and other regions of the world.

In addition to the clinical history, skin testing and/or drug challenges are an important component in the evaluation and management of adverse drug reactions. Although skin testing to drugs plays an important role in the evaluation and management of adverse drug reactions, the diagnostic value of skin testing to various medications is dependent on the drug of interest. The best studied skin testing to a medication is penicillin, which has been shown to have a >90% negative predictive value for IgE-mediated adverse drug reactions. Drug challenges to the medication are the gold standard in determining the culprit medication and/or to determine the tolerance of medications in the evaluation and management of adverse drug reactions and have been shown to be safe when performed by a trained professional in the appropriate clinical situation. In this chapter, we describe and discuss the role of skin testing and/or drug challenges of various medications in the evaluation and management of adverse drug reactions.