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Abstract:
Human infection by Strongyloides stercoralis can manifest with dermatological, intestinal and pulmonal symptoms frequently passing into a chronic disease. Low parasitic loads and discontinuous larvae excretion hamper diagnosis by coproscopy. To detect infection, serological test systems are much more sensitive, however, assays commonly based on native antigens from Strongyloides ratti larvae and lack specificity. Lysate from S. papillosus was used for the Anti-Strongyloides ELISA IgG. ELISA performance was evaluated by participation in an external quality assessment scheme (NEQAS, UK) encompassing three positive and three negative samples, a correlation with commercial Bordier-ELISA (Strongyloides ELISA kit based on S. ratti antigens) through testing of 58 pre-characterized sera and the comparison with an inhouse developed S. ratti-based ELISA determining specificities with respect to a cross reactivity panel (193 samples from patients with other parasitic or bacterial infections) and a control panel (samples from 500 blood donors, 100 pregnant women and 88 children). Results obtained with Anti- Strongyloides ELISA were in 100% agreement with the quality assessment target values. Furthermore, in 48 of 58 samples (82.7%), the result of the Anti-Stronygloides ELISA correlated with the pre- characterization by Bordier-ELISA. Serological analysis of discrepant cases (positive with Bordier-ELISA but negative with Anti-Strongyloides ELISA) indicated infections with Plasmodium ssp. as well as with Schistosoma ssp. The S. ratti-based ELISA was reactive in 13.9% of sera in the cross reactivity panel and in 10.6% of the samples from healthy individuals, yielding a combined specificity of 88.6%. In comparison, reactivities of 6.2% (cross reactivity panel) and 3.5% (healthy controls) were detected with the Anti- Strongyloides ELISA. The use of native antigens from S. papillosus increases assay specificity.
