Value of Basophil Activation Test for Evaluating Immediate Reactions to Proton Pump Inhibitors

Rationale: Proton pump inhibitors (PPI) are widely used and although allergic reactions to them are rare, the incidence has increased in recent years. Most publications describe isolated cases and limited data are available about the value of skin tests. Therefore, the diagnostic approach is the drug provocation test (DPT), which is not risk free given that reactions can be severe. The aim of the study was to assess the value of the basophil activation test (BAT) for the diagnosis of immediate allergic reactions to PPI.

Methods: We evaluated 20 patients with confirmed immediate allergic reactions to PPI. Patients with anaphylaxis or shock were diagnosed by clinical history, once other possible causes were ruled out, and those with urticaria by DPT. BAT with omeprazole, lansoprazole, and pantoprazole were performed in all patients and in 14 subjects with good tolerance to PPI.

Results: The PPIs involved were omeprazole (N=18) and lansoprazole (N=2). A total of 11 cases (55%) reported anaphylaxis, 7 (35%) anaphylactic shock and 2 (10%) urticaria. BAT was positive in 16 cases (66.66%): 13 (81.25%) to omeprazole, 6 (37.5%) to pantoprazole and 2 (12.5%) to lansoprazole. No differences were found in the time between the reaction and the study comparing those patients who gave a positive BAT results and those who were negative. BAT specificity was 78.57%. 

Conclusions: Immediate hypersensitivity reactions to PPI do occur, with omeprazole being the drug most frequently involved and anaphylaxis the most common clinical entity. BAT is a useful method for diagnosing these patients.