Evaluation of the circumoval precipitin test using dried blood on filter paper as a diagnostic tool in epidemiological survey for schistosomiasis.

ABSTRACT

The suitability of the circumoval precipitin (COP) test in a field survey for schistosomiasis in the rural area using dried blood samples on filter paper was evaluated with reference to the stool examination by the merthiolate-iodine-formaldehyde concentration (MIFC) technique. Both blood and stool samples were collected simultaneously among over 600 inhabitants of two schistosomiasis endemic communities (barrios) of Palo, Leyte, Philippines. The method of collecting blood samples on filter paper, the procedure for COP test and its sensitivity in detecting schistosomiasis cases are described. Blood sampling from finger prick was acceptable to both adults and children so that blood samples were readily obtained while the collection of stool samples required repeated visits to the homes. A significantly higher percentage of schistosomiasis positives were obtained by COP test than by stool examination. The COP test results were comparable to the stool examination results on the following aspects 1) highest infection rate in the 10-19 age group and lowest infection rate in the 60 years old and above; 2) positive rates for schistosomiasis did not differ significantly between the two barrios and 3) no family accumulation of the disease in the two communities was observed in this survey in 1972. The stability of the antibody in filter paper, the reliability of the test and the simple and rapid procedures involved make this filter paper method of COP test very practical and suitable for schistosomiasis survey in rural areas.