7-2.a. Value of skin tests
Brajon et al.83 have reported the non-irritating concentrations of PPI used in patch tests prepared with commercially available forms of PPIs.In literature, there are different suggested concentrations to perform patch test with PPIs preparation47, but these data cannot be compared with each other as the active PPI concentration in the final preparation is not known. We advise that capsules always contain gastro-resistant granules, which are difficult to be crushed and that PPI concentration in the granules is low. In regards, Brajon et al., after diluting the granules/tablets reduced in powder at 30% in petrolatum, demonstrated that the final active PPI concentrations in patch tests were esomeprazole at 2.92% (diluting Inexium® 40 mg tablet), omeprazole at 2.59% (Mopral® 10 mg capsule) and pantoprazole at 6.09% (Eupantol® 40 mg tablet).83
According to recommendations for drug patch test preparations,84 we recommend to reduce granules/tablets to a fine powder, dilute this material at 30% in petrolatum, and note the final concentration of the active ingredient. In case of PPIs that exist in injectable forms (esomeprazole and pantoprazole), it is recommended to dilute them at 10% in petrolatum.
Positive patch tests results have been mainly reported in DRESS.71,76 The value of SPT and İDT with delayed readings have not been investigated in delayed reactions to PPI.
Classification into 2 PPI subgroups, the omeprazole group (omeprazole/ esomeprazole/ pantoprazole) and the structurally similar lansoprazole group (lansoprazole/ dexlansoprazole/rabeprazole), may explain the cross-reactivity in delayed HS. Among 16 reintroductions in 15 patients with delayed HSRs, the cross-reactivity was studied by Lin et al71. In 13 cases (10 MPE, 2 SJS/TEN, 1 DRESS), there were no cross-reactions between structurally different PPIs. In 3 other cases (1 MPE, 1 SJS/TEN, 1 DRESS), the reintroduction of PPIs belonging to the same group as the causative PPI induced a relapse of the reaction. Data is too scarce to make recommendations, but, these preliminary results suggest that in cases of delayed HSRs switching to a structurally different PPI should be considered.