A new serological technique, time-resolved fluoroimmunoassay (TRFIA), for the immunological diagnosis of urinary schistosomiasis

Abstract

The application of a new serological method, time-resolved fluoroimmunoassay (TRFIA), is described for the diagnosis of urinary schistosomiasis. A chelate of lanthanides (europium) with a long fluorescent life-time is used as label. The intensity of fluorescence is measured after a delay selected to eliminate almost completely the background fluorescence, which decays rapidly. TRFIA was compared with an established method, enzyme linked immunosorbent assay (ELISA). Using sera from proven cases of Schistosoma haematobium infection, 98.1% of the samples were positive by TRFIA and 86.5% by ELISA. Sera from patients infected with helminths other than schistosomes produced only 1.5% of false positives with TRFIA, compared with 12.3% by ELISA. TRFIA is more sensitive and specific than ELISA.