Fast-dot ELISA using urine, a rapid and dependable field assay for diagnosis of schistosomiasis

ABSTRACT

The fast dot-enzyme linked immunosorbent assay [FD-ELISA] was used as a field applicable tool for rapid diagnosis of schistosomiasis. 700 fecal specimens were parasitologically examined for detection of S. mansoni eggs and other parasitic infection. Egg count was done for 100 infected patients. Rectal biopsies [394] were taken from individuals with no S. mansoni egg in their stool where it was used as golden standard for diagnosis of schistosomiasis. Cross- reactivity with other parasites was studied. Serum samples were tested by ELISA technique for detection of human IgG anti-schistosomal antibodies. 700 urine samples [433 S. mansoni infected patients and 267 healthy individuals] were tested by FD-ELISA for detection of a schistosomal antigen excreted in urine using BRLF4 mouse monoclonal antibody. FD- ELISA results were compared with ELISA detecting antischistosomal IgG and stool analysis where it showed highest efficiency [91%] compared with 81% and 60% for ELISA and stool analysis, respectively. The sensitivity of FD-ELISA was high ranging from 90 to 94% in the 4 different clinical stages of schistosomiasis [simple intestinal, hepatosplenomegaly, shrunken liver and splenomegaly, and shrunken liver-splenomegaly and ascites]. FD-ELISA was highly sensitive, detecting infection cases with 20 eggs/g feces and its specificity was 89%. The antigen was characterized as a protein with a molecular weight of 74 KDa using Western Blot technique