AbstractSome serology assays demonstrated useful for post-treatment monitoring of Strongyloides stercoralisinfection. Serology frequently has low specificity, which might be improved by the use ofrecombinant antigens. The Strongy Detect ELISA is based on two recombinant antigens (SsIR andNIE) and proved good accuracy. Aim of this study was to evaluate the performance of this test forthe post-treatment monitoring of strongyloidiasis. We tested 38 paired sera, with matched fecal testsresults, stored in our biobank and originating from a randomized controlled trial. At baseline, allpatients tested positive for at least one fecal assay among PCR, direct stool microscopy and agar plateculture. Patients were re-tested with both serology and fecal assays 12 months after treatment.Primary outcome was the relative reduction in optical density (OD) between baseline and follow up.We observed that about 95% samples showed a reduction between pre and post-treatment OD, witha median relative reduction of 93.9% (IQR 77.3% - 98.1%). In conclusion, the test proved reliablefor post-treatment monitoring. However, some technical issues, including that the threshold forpositivity has not be predefined, and that a substantial number of samples showed overflow signals,need to be fixed to permit use in routine practice.Key wordsStrongyloides; strongyloidiasis; ELISA; serology; follow up