Indirect screening for Schistosoma haematobium infection: a comparative study in Ghana and Zambia

Four indirect approaches, based on inquiry into a past history of haematuria, visual inspection for blood in the urine specimens, and the use of reagent strips to detect haematuria and proteinuria, were evaluated to identify persons with Schistosoma haematobium infection. These approaches were applied individually and in three different screening sequences on two populations in Ghana and Zambia in order to identify infected children and adults for subsequent treatment in both areas. Detection of haematuria using reagent strips was the single approach with the highest sensitivity and specificity. The observation of gross haematuria (bloody urine), followed by detection of blood by reagent strips, identified 87% of infected children in both areas. This screening sequence showed the highest combined sensitivity and specificity in the identification of infected children as well as adults for treatment in both areas. Differences in the results between the two countries are discussed. This study emphasizes the need for evaluation of indirect screening procedures for the diagnosis of S. haematobium infection in each endemic area so as to establish criteria for their interpretation, prior to large-scale field application.