Detection of Wuchereria bancrofti antigen in serum and finger prick blood samples by enzyme immunoassay: field evaluation.

We have recently reported that a monoclonal antibody-based enzyme immunoassay for detection of filarial antigen in human serum is sensitive and specific for active infection with Wuchereria bancrofti. The present studies were undertaken to assess the feasibility of testing whole blood collected by finger prick in this assay. A preliminary study was performed to compare antigen test results obtained with whole blood, blood dried on filter paper, and serum. Results obtained with anticoagulated whole blood specimens agrees with serum results in 94 of 97 cases. All whole blood and serum specimens from 28 people with positive microfilaria smears were positive in the test. Filter paper blood specimens were less satisfactory because of decreased sensitivity and specificity. A population-based survey of 1009 persons was conducted in a village near Calicut, India, to evaluate the use of finger prick blood specimens for filarial antigen detection in field studies. Thirty-eight of 39 microfilaria carriers had positive antigen tests. In addition, 10.7% of amicrofilaremic endemic controls had positive tests. Additional studies are needed to test the hypothesis that filarial antigenemia in endemic controls indicates the presence of subclinical infection.