The role of basophil activation test in special populations with mastocytosis and reactions to hymenoptera sting

Background Systemic mastocytosis (SM) may be associated with hymenoptera allergy. In such cases, immunotherapy is a life-saving treatment, but a circumstantiated diagnosis is needed for its prescription. Patients with SM and previous reactions to stings, but with negative tests represent a diagnostic dilemma. The basophil activation test (BAT) may be helpful in refining the diagnosis. Objective We assessed the usefulness of BAT in subpopulations of mastocytosis patients, including those with negative tests for insect allergy. Methods Within a population of patients with mastocytosis and previous stings, we studied by BAT and augmented intradermal test (IDT) (10 mu g/ml) two groups: (1) with reactions to stings and negative tests; (2) without reactions and negative tests. Basophil activation test was performed with different venoms, assessing at flow cytometry basophils activation. Results Sixty-three patients had mastocytosis and 52 had reactions to previous hymenoptera stings. Of them, seven proved negative to diagnostic tests. In six of seven of those patients, BAT was negative with all venoms, and in one, basophils resulted activated also with the negative control. In six patients without previous reactions and negative tests, BAT was totally negative in five of six patients and weakly positive to Hornet in one. Finally, the IDT at 10 mu g/ml venom produced nonspecific positive results in most cases. Conclusion In patients with mastocytosis, the negative results of standard tests are reliable, because BAT and IDT at higher concentration do not add useful information.