Application of enzyme immunoassay for postchemotherapy evaluation of human strongyloidiasis.

Posttherapy evaluation of strongyloidiasis is frequently difficult because coprologic examination is not sensitive enough for diagnosis of chronic infection. In the present study, anti-Strongyloides enzyme-linked immunosorbent assay antibodies were monitored before and after treatment with thiabendazole and pyrvinium pamoate in 199 patients with chronic strongyloidiasis in Okinawa, Japan. A significant decrease in antibody levels was observed in patients who became negative for fecal larvae after the treatment, whereas the antibody levels did not show a significant change after the treatment in patients who were still harboring the parasite. In the group coprologically negative in the follow-up examination, however, many individuals did not show a significant fall in antibody titers after treatment, which suggests that these cases were equivocal for complete cure. By the subsequent fecal reexamination performed on the equivocal cases, approximately 20% were additionally found to be still harboring the parasite. These results indicate that serologic testing is useful to check whether a real cure has been achieved among the patients in whose fecal samples the presence of larvae has not been demonstrated after treatment.