Improving the detection limit of quantitative diagnosis of anti-S. haematobium antibodies using Falcon Assay Screening Test (FAST) ELISA by developing a new standard curve.

Immunodiagnosis of schistosomiasis are currently based on parasitological examinations of stool and urine for egg detection, which is laborious and lacks sensitivity. There are many assays that detect the anti-schistosomal antibodies in patient sera. One of these assays is the Falcon assay screening test (FAST) ELISA that uses adult worm microsomal antigen for Schistosoma haematobium and Schistosoma mansoni, HAMA, MAMA antigen, respectively. This assay depends on quantitative detection of anti-schistosome antibodies, using a standard curve, but the detection limit of FAST-HAMA assay is low due to the small range of the standard curve. In our study, a new wide range (0-80 µl/µl) of standard curve for FAST-HAMA assay was constructed, and the cut-off value of the assay, using the new curve, was determined to be 1.2 units/µl. Screening of 41 S. haematobium-infected sera with FAST-HAMA, using the new constructed curve, showed a sensitivity of 95%. The purity of HAMA antigen and highly specific Abs for S. haematobium lends the FAST-HAMA with the new constructed wide range standard curve as a diagnostic assay with high detection limit for S. haematobium infection.