Antibody Detection
Immunodiagnostic tests for strongyloidiasis are indicated when the infection is suspected and the organism cannot be demonstrated by duodenal aspiration, string tests, or by repeated examinations of stool.  Antibody detection tests should use antigens derived from Strongyloides stercoralis filariform larvae for the highest sensitivity and specificity.  Although indirect fluorescent antibody (IFA) and indirect hemagglutination (IHA) tests have been used, enzyme immunoassay (EIA) is currently recommended because of its greater sensitivity (90%).  Immunocompromised persons with disseminated strongyloidiasis usually have detectable IgG antibodies despite their immunodepression.  Cross-reactions in patients with filariasis and some other nematode infections may occur.  Antibody test results cannot be used to differentiate between past and current infection.  A positive test warrants continuing efforts to establish a parasitological diagnosis followed by antihelminthic treatment.  Serologic monitoring may be useful in the follow-up of immunocompetent treated patients: antibody levels decrease markedly within 6 months after successful chemotherapy.

Reference:

Genta RM. Predictive value of an enzyme-linked immunosorbent assay (ELISA) for the serodiagnosis of strongyloidiasis. Am J Clin Pathol 1988;89:391-394.