Diagnosis approach to hypersensitivity reactions in Helicobacter pylori eradication

Background: Helicobacter pylori (HP) infection is treated with a combination of antibiotics and antisecretory agents. Hypersensitivity reactions (HSR) limit therapeutic options. This study characterizes the diagnostic approach of HSR to HP eradication therapy. Methods: Retrospective analysis (1/2011–6/2024) of patients with suspected HSR to HP eradication therapy (proton pump inhibitors (PPI) + amoxicillin + clarithromycin or PPI + amoxicillin + clarithromycin + metronidazole). Diagnosis was considered: 1) confirmed by a suggestive clinical history (CH) and positive specific IgE to β-lactams (βL sIgE) or positive skin tests [skin prick tests (SPT), intradermal tests (IDT), epicutaneous tests], or based on a positive drug provocation test (DPT); 2) probable based on suggestive CH and positive lymphocyte transformation test (LTT); or 3) excluded by negative DPT or non-suggestive CH. Results: Of 42 patients [88% female, mean (range) age 55 years old (22-85)], 10 had immediate HSR: five had anaphylaxis, five had urticarial rash. Amoxicillin HSR diagnosis was confirmed in seven of these patients (two based on βL sIgE, two on βL sIgE /SPTs, one on SPT, two on IDTs) and excluded by DPT in three. HSRs to clarithromycin, metronidazole, and PPIs were excluded in all patients. Non-immediate HSRs were reported in 32 patients. Amoxicillin HSRs diagnosis was confirmed in five of these patients based on DPT and considered probable in one (based on LTT). Clarithromycin HSR was confirmed in two patients by DPT, and PPI (omeprazole) HSR in one patient by DPT. Conclusion: Clinical history alone overestimates HSR. Amoxicillin was the most frequent etiology of immediate and non-immediate HSRs. Immediate HSRs were diagnosed using sIgE and skin tests, while non-immediate HSRs relied on DPT. In both groups, DPT was necessary to exclude hypersensitivity.