Evaluation of whole blood collection methods using the og4c3 ELISA in bancroftian filariasis

Venous blood samples were collected as part of the Papua New Guinean Filariasis Elimination Programme and the serum tested by the Trop-Ag W. bancrofti test kit for antigen. Before the blood clotted, whole blood was tested by the ICT and also added to filter paper where it was dried, transported back to Townsville, Australia and tested by the TropBio ELISA. The positive percent agreements (PPA), with the TropBio serum assay, of the ICT and filter paper technique were 63.6% (95% confidence interval [CI], 58.6%-68.4%) and 67.2% (95% CI, 62.1%-72.1%). The negative percent agreements were (NPA) 97.6% (95% CI, 95.7%-98.9%) and 99.2% (95% CI, 97.8%-99.8%) respectively. The sensitivity was 88.6%(95% CI, 82.0%-93.5%) and 88.4% (95% CI, 81.4%-93.5%) compared to microfilaraemia as determined by a 60 ul blood film. A sample of ICT tests had the filter paper removed and tested by the Trop-Ag W. bancrofti filter paper test. There was no significant difference (P=0.23) in the PPA between the ICT, blood collected onto filter paper and using filter paper from the ICT for this sample set. A fast friendly field (FFF) version of the Trop-Ag W. bancrofti test kit was trialled in Bougainville after it was shown that the boiling step was unnecessary in the procedure. The positive percentage agreement using 250 serum specimens compared to the boiled supernatant was 94.6% (CI, 88.7-98.0) and negative percentage agreement (NPA) 97.1% (CI, 92.8-99.2) with a significant correlation between optical densities (r=0.97, P<0.001). For the FFF assay, whole blood was added to an ELISA plate, incubated overnight and then processed in the field using reagents supplied in dropper bottles. Reactions were read by eye and compared to the TropBio assay. The PPA was 96.0% (95% CI, 79.7%-99.9%) and the NPA 98.4% (95% CI, 94.2%-99.8%). The FFF is suitable for use with capillary collection and is simple to perform unlike the filter paper collection which is labour intensive. The FFF could be a suitable field alternative for the ICT.

American Journal of Tropical Medicine and Hygiene

American Journal of Tropical Medicine and Hygiene

77

1476-1645

N/A

5 (suppl)

1