An enzyme-linked immunosorbent assay using Schistosoma mansoni purified egg antigen for the diagnosis of schistosomiasis in Saudi Arabia.

The enzyme-linked immunosorbent assay (ELISA) using purified Schistosoma mansoni egg antigen (CEF6) was compared with standard parasitological diagnostic tests (potassium hydroxide digestion of faeces and urine filtration) for diagnosis of schistosomiasis in humans in Saudi Arabia. Faecal, urine and finger-prick blood samples were collected from 2 groups of individuals of both sexes, aged 1-50 years, in 2 areas in the western region of Saudi Arabia: 983 in a schistosomiasis endemic area (Al-Hijaz highlands) and 192 in a non-endemic area (Jeddah). In the non-endemic area, almost 90% of the blood samples gave optical density readings at 492 nm (OD) < 0.25. The mean OD in the schistosome endemic area (0.31) was much higher than in the non-endemic area (0.14). The prevalence of S. mansoni infection by faecal examination in the endemic area was 10.2% and the specificity and sensitivity of the ELISA using a cut-off OD of 0.25 were 55% and 90%, respectively. In the endemic area, there was a positive correlation between egg intensity and OD value. No S. haematobium was detected. In the non-endemic area, the specificity was 90%. The main reasons for false positive results may have been inapparent or cured S. mansoni infection.