Evaluation of an immunoenzymatic assay detecting specific anti-Toxocara immunoglobulin E for diagnosis and posttreatment follow-up of human toxocariasis.

In order to complete the immunodiagnosis of human toxocaral disease, an immunoenzymatic assay with excretory-secretory antigens from Toxocara canis larvae was developed for the detection of specific immunoglobulin E (sIgE enzyme-linked immunosorbent assay [ELISA]). The specificity of the assay was evaluated in patients presenting with various allergic or helminthic diseases. The sensitivity was assessed in patients exhibiting clinical and biological symptoms indicative of toxocariasis, serodiagnosis of which was made by the Western blot (WB; immunoblot) procedure that used the same antigen as that used in the sIgE ELISA but that detected specific IgG. The value of the sIgE ELISA for posttreatment follow-up was tested in two groups of patients: one group was treated with diethylcarbamazine; the other group was not treated with DEC. Results showed that the specificity and sensitivity of the sIgE ELISA were moderate. Thus, the sIgE ELISA appeared to be insufficient for properly ensuring the serodiagnosis of toxocariasis when it is used alone. However, sIgE ELISA might be an interesting complementary method for the detection of specific IgG. It was the only assay that was found to be positive in sera from some hypereosinophilic patients. sIgE ELISA values decreased significantly among the patients treated with DEC, indicating that this test would be useful for posttreatment follow-up assessment.