Hypersensitivity reactions to non-vitamin K oral anticoagulants - a review of literature and diagnostic work-up proposal

Non-vitamin K antagonist oral anticoagulants (NOACs) are increasingly being used in hospital and outpatient settings as safe alternatives to warfarin. Hypersensitivity reactions have been described for NOACs and can be classified according to Gell and Coombs. We reviewed case reports of possible drug hypersensitivity reactions, noticing a predominance of delayed reactions (both mild and severe) and the absence of cross-reactions to warfarin and low molecular weight heparins. International experience on diagnostic tests is lacking. The vast majority of authors refer to probability scores and rely on biopsy to classify vasculitis and rule out differential diagnoses. We propose to adapt available tests to confirm the patient's reactivity to new anticoagulants. Among in vivo tests, patch testing revealed promising in delayed reactions.