Assessment of Two Commercial Serological Assays for the Diagnosis and Post-Treatment Follow-Up of Strongyloidiasis in a Cohort of Patients with Chagas Disease

Strongyloidiasis is a neglected tropical disease that frequently coexists with Chagas disease (CD) among individuals from Latin America. Serology is increasingly used for the diagnosis and post-treatment follow-up of strongyloidiasis; however, comparative data on commercially available assays remain limited. We conducted a cross-sectional evaluation in a cohort of fifty-five patients with previously treated CD attending a Tropical Medicine Unit in Spain. All patients underwent serological screening for Strongyloides stercoralis using two commercial ELISA assays: the Strongyloides IgG ELISA kit (DRG Instruments GmbH) (DRG) and Anti-Strongyloides ELISA IgG (Euroimmun Medizinische Labordiagnostika AG) (Euroimmun). A composite reference standard defined infection as seropositivity in combination with eosinophil count (>0.5 × 103 eosinophils per µL) or seropositivity in both assays. Infected individuals received ivermectin and were reassessed one-year post-treatment. Thirty-seven patients (67.3%) met the criteria for strongyloidiasis. Concordance between the assays was substantial (κ = 0.80). According to the composite study definition, both assays identified most patients as infected. At one-year follow-up, significant reductions were observed in DRG and Euroimmun indexes, as well as in eosinophil count (all p < 0.001). Treatment response rates were 83.3% with DRG and 73.3% with Euroimmun. Both ELISA assays showed comparable performance in identifying patients at risk of strongyloidiasis and in monitoring serological response after ivermectin treatment, supporting their usefulness in the management of patients with CD and suspected strongyloidiasis. Routine serological screening should be considered in this high-risk population.