6.2.c. Value of in vitro tests
To date, there are no studies on the determination of specific IgE
antibodies to PPI and, therefore, they are not available in the most
widely used commercial platform for specific IgE determination to drugs,
the ImmunoCAP system (Thermo-Fisher, Uppsala, Sweden). A promising tool
for the diagnosis of immediate allergic reactions to PPI is the basophil
activation test (BAT)19,21,38, which determine the
basophil activation upon stimulation with the culprit drug or its
metabolites by flow cytometry. \soutFor that Different strategies to
identify basophils (anti-IgE, CCR3, CRTH2 and CD203c) and to measure
their activation (CD63 and CD203c) have been
proposed.62 Gamboa et al. were the first to report a
positive BAT result to omeprazole in a patient who developed immediate
urticaria and angioedema after the drug intake, result concordant with
the positive skin test result.21 Later, a second case
report of a patient with anaphylaxis after omeprazole administration
confirmed the usefulness of BAT by detecting a positive result for the
culprit PPI and negative results in healthy
controls.38 Laguna et al. analyzed in detail the role
of BAT, using CD63, for the diagnosis of 42 patients with immediate
omeprazole allergy confirmed by ST or DPT and 22 age- and sex-matched
healthy controls.19 They detected a BAT sensitivity of
73.8%, a specificity of 100%, a PPV of 100% and a NPV of 66.7%.
Moreover, BAT was positive in 57.1% of patients with negative ST and by
combining ST and BAT it was possible to reach a confident diagnosis of
PPI HSRs in 85.7% of patients. There are no studies with other PPIs.