Characterization of subjects experiencing selective hypersensitivity reactions to non-steroidal anti-inflammatory drugs (NSAIDs)

Selective hypersensitivity reactions (SHR) are the second most frequent NSAID-induced hypersensitivity. Our aim was to characterize a group of patients with SHR to NSAIDs, analyzing symptoms, culprit drugs and diagnostic methods. We verified acetylsalicylic acid (ASA)-tolerance and classified patients as single NSAID-induced urticaria/angioedema/anaphylaxis (SNIUAA) or single-NSAID-induced delayed hypersensitivity reactions (SNIDHR) whether the symptoms appeared less or more than 24 hours after NSAIDs administration. In metamizole-induced- SNIUAA, we performed skin tests (STs), and if negative basophil activation test (BAT) was performed. When these tests were or other drugs were involved with <2 episodes reported, drug provocation test (DPT) with the culprit was performed. We included 518 patients with a mean age of 43 (31.25-54) years, 459 SNIUAA and 59 SNIDHR, and 66.2% were female. In SNIUAA, anaphylaxis (32.4%) was the most frequent entity, and in SNIDHR was maculopapular exanthema (44.1%). Metamizole was the most frequent culprit in SNIUAA (39.7%, p=0.003) and propionic acids in SNIDHR (46.8%, p>0.05). In 11.2% patients, DPT with the culprit was performed. In 60.4% patients, diagnosis was established by a history of repeated episodes (76.3% SNIDHR vs 63.6% SNIUAA, p>0.05). STs with metamizole was positive for 72% SNIUAA and for 57.1% SNIDHR (p>0.05). BAT was positive in 25.8% metamizole-induced SNIUAA patients with negative STs. SNIUAA to metamizole is the most frequent type of NSAID-induced SHR. Although STs and BAT may aid in the diagnosis of these reactions, their sensitivity is low. Further research is needed to develop better diagnostic tools.