Serological diagnosis of strongyloidiasis: An evaluation of three commercial assays.

Background: Strongyloidiasis is caused by a neglected nematode, manifesting as chronic intestinal infection with potentially severe manifestations. The disease is an emerging problem in non-endemic countries affecting travelers and migrants. Diagnosis of strongyloidiasis is hampered by the lack of standardization and absence of a gold standard. Since adequate direct methods to detect the motile larvae in stool samples are not widely available, other techniques such as serology have been developed. Methods: We evaluated three commercial ELISA kits (DRG Instruments, IVD Research, and Bordier Affinity Products) to detect IgG antibodies against Strongyloides stercoralis assays utilizing serum samples from travelers with microscopically confirmed strongyloidiasis (n = 50) and other imported helminthic infections (n = 159) as well as healthy controls (n = 50). Results: The DRG, IVD, and Bordier assays showed sensitivities of 58.0%, 64.0%, and 56.0%, respectively. Specificity values were 96.0%, 96.0%, and 92.0% in healthy controls, and 67.3%, 62.9%, and 76.7% in cases with other helminth infections, respectively. Cross-reactions were mostly observed in cases with other nematodes (37.5%, 42.5%, and 20.0%, respectively), but also in trematode (33.3%, 38.1%, and 19.0%, respectively) and in cestode infections (25.0%, 30.0%, and 32.5%, respectively). Conclusion: The study demonstrates the diagnostic limitations of serological assays to detect or exclude cases of strongyloidiasis in returning travelers, who frequently present with recent or acute infections. Author summary: Strongyloidiasis is a neglected nematode infection, which causes significant morbidity and mortality due its chronic course and potential of severe manifestations. The disease mostly threatens inhabitants of tropical and subtropical regions. Moreover, it has been recognized as an emerging problem in industrialized countries affecting migrants and returning travelers. The diagnosis of the intestinal helminth is challenging, since its reliable detection in stool samples requires specific methods, which are mostly not performed. Antibody detection by serological tests is a practical and commercially available diagnostic alternative, but the capabilities of such tests in non-endemic regions are not sufficiently studied. The presented study evaluated the performance of three commercial Strongyloides ELISA kits using serum samples from travelers with proven strongyloidiasis or various other parasitic infections. The study revealed that the sensitivity of Strongyloides serology in patients from non-endemic countries, who often present with early infections, might be limited and that tests frequently cross-react with other helminth infections. Serological results should therefore be interpreted cautiously and used together with parasitological methods to reduce the risk of missing this potentially severe infection. [ABSTRACT FROM AUTHOR]