Background: The single-blind, placebo controlled oral challenge (SBPCOC) is the definitive way to diagnosis nonsteroidal anti-inflammatorydrug (NSAID)-induced reactions.

Objective: To evaluate 223 NSAID-sensitive patients by means of SBPCOC, and to describe the main clinical patterns found.

Methods: A prospective study was carried out, including 2 patient groups with case histories consistent with NSAID-induced reactions. Of the 223 patients, 174 were diagnosed on the basis of a positive SBPCOC. The second group consisted of 49 patients who were referred because of a documented history of anaphylaxis after taking NSAIDs, and these underwent SBPCOC with potent cyclooxygenase (COX)-1/COX-2 inhibitors, except those reported as being responsible for the reaction. The type of SBPCOC reaction, the NSAID reactivity pattern, and the associated diseases were the main classification criteria.

Results: Two broad categories of NSAID-induced reactions were identified: the cross-reactive and selective syndromes. The 150 patients who showed cross-reactive syndromes included 3 types of diseases: type 1, patients with rhinitis and/or asthma who developed nasoocular and/or asthmatic reactions (n=40); type 2, patients with or without chronic urticaria who presented urticaria/angioedema (n=59); and type 3, atopic patients with isolated periorbital angioedema (n=51). In contrast, the selective syndromes, or type 4, included 50 patients who developed anaphylaxis, as well as 11 patients with urticaria during SBPCOC. Finally, a miscellaneous group of reactions not matching any of the above types was identified (n=12).

Conclusions: NSAID-sensitive patients can be classifi ed into 4 different groups of reactors, each with well-defi ned clinical characteristics. Thus, a clinical classification of this NSAID-induced reaction complex is proposed.

Key Words: NSAID sensitivity. Asthma. Nasoocular reaction. Angioedema. Urticaria. Anaphylaxis. Classifi cation..