Evaluation of a novel rapid diagnostic test for Schistosoma haematobium based on the detection of human immunoglobulins bound to filtered Schistosoma haematobium eggs

摘要

Objectives: To determine whether the detection of human IgG bound to Schistosoma haematobium eggs from filtered urine could be used as a rapid diagnostic test (RDT-Sh). Methods: We filtered 160 urine samples from children in the Kwale District of Kenya to isolate S. haematobium eggs and used anti-human IgG antibody conjugated to horseradish peroxidase to bind to the human IgG attached to the eggs. We then added 3,3′5,5′-tetramethylbenzidine base (TMB), which turns blue in the presence of horseradish peroxidase to detect the S. haematobium eggs. The RDT-Sh was compared in a blinded manner to urine microscopy. Results: The RDT-Sh was positive in 89% of urine samples containing >1 egg/10 ml (58/65 samples) and 97% of urine samples containing >11 eggs/10 ml urine (35/36 samples) seen by microscopy. The RDT-Sh was negative 79% of the time when no eggs were seen on urine microscopy, but because up to three times more urine was used for the RDT-Sh, there were likely cases in which eggs were on the RDT-Sh filter but not detected by microscopy. We used latent class analysis incorporating urine microscopy, haematuria, proteinuria and RDT-Sh results to determine an overall 97% sensitivity and 78% specificity for RDT-Sh, 96% and 81% for urine microscopy, 71% and 98% for microscopic haematuria and 46% and 89% for proteinuria, respectively. Conclusions: The RDT-Sh is quick, inexpensive and easy to perform in the field for the diagnosis of S. haematobium.