Evaluation of Enzyme- linked Immunosorbaent Assay, Using Somatic and Excretory-Secretory Antigens of Strongyloides stercoralis for the Serodiagnosis of Strongyloidosis

Abstract

Strongyloidiasis, caused by a nematode parasite so-called Strongyloides stercoralis is one of the major human intestinal nematode infections. Considering that stool examination for Strongyloides larvae is not a sensitive method and immunodiagnostic methods are more applicable for this purpose, so the present study was conducted to compare the somatic (S) and excretory - secretory (ES) antigens of Strongyloides stercoralis in IgG-ELISA to diagnose human strongyloidiasis. Serum samples obtained from 50 individuals infected with Strongyloides stercoralis. Sera from healthy control individuals, not infected with any parasitic diseases (n=/30) and from others with different parasitic infections including hydatidosis (n=20), toxocariosis (n=18), ascariasis (n=2), trichostrongylosis (n=10), and hymenolepiasis (n=2) were examined as well. The cut-off point for (S) and ES was 0.48 and 0.36, respectively. Thirty eight and 42 out of 50 individuals infected with Strongyloides stercoralis were also seropositive using (S) and ES antigens, in that order, whereas 15 cases of false positive reactions for (S) and 10 for ES antigen were detected when non-strongyloidiasis sera were examined, therefore the sensitivity of the test was 80.6% and 86.2% for (S) and ES antigens, respectively. The specificity of those antigens was calculated as 84.2% and 88.2%, correspondingly. It was concluded that overall ES antigen showed a more convincing diagnosis in comparison with (S) antigen, although every interpretation of the results should be in accompany with clinical manifestations and a history of the disease.