The diagnosis of cystic echinococcosis (CE) is based on imaging, while serology is a complementary test of particular use when imaging is inconclusive. Serology has several limitations. Among them, false-positive results are often obtained in subjects with alveolar echinococcosis (AE), rendering difficult the differential diagnosis. We set up an immune assay based on IL-4-specific production after stimulating whole blood with an antigen B (AgB)-enriched fraction from E granulosus that associates with CE and CE cysts in active stage. We aimed to evaluate potential cross-reactivity of this test using samples from patients with AE. Twelve patients with AE were recruited; IL-4 levels ranged from 0 to 0.07 pg/mL. Based on the previously identified cut-off of 0.39 pg/mL using samples from patients with CE, none of samples from AE patients scored positive. In contrast, almost 80% of samples from AE patients scored positive in serology tests based on different E granulosus-derived antigenic preparations. Our preliminary data show that this experimental whole-blood assay has no cross-reactivity in our cohort of patients with AE, in turn indicating a high specificity of the assay for CE diagnosis. This result supports further work towards the development of improved diagnostic tests for CE.