Background: In a previous study an IgE ELISA test for hydatidosis was standardized and evidenced high sensitivity (95.6%) and specificity (100%) and encouraging results for the diagnosis and follow up of patients treated with albendazole. Objectives: To confirm efficacy of IgE antibody level determination in patients with cystic echinococcosis treated with albendazole and considered clinically cured and ultrasonographically improved, or recurrence in patients considered improved or cured. Design: Longitudinal, retrospective-prospective, quasi-experimental study, longitudinal study, with pre- and post-test for assessing diagnosis and monitoring in the prospective group, and follow-up and recurrence in both groups. Setting: Instituto de Medicina Tropical "Daniel A. Carrión", Universidad Nacional Mayor de San Marcos, Lima, Peru. Participants: Patients with cystic echinococcosis. Methods: S...