ABSTRACT
To determine if enzyme linked immunosorbent assay [ELISA] could be used to test dried blood spot samples for hepatitis B surface antigen [HBsAg], blood samples from known negative individuals were collected and used for blood and serum spotting on filter paper with comparison to the standard serum assay. Significantly higher absorbance values were obtained from blood spots on filter paper when compared to serum spots and the whole serum. Different modification techniques were used to determine if they could be used to reduce the background absorbance. The modifications tested were: i] use of casein solution, ii] separate incubation of samples and conjugate [with or without increased volume iii] centrifugation iv] centrifugation and heating. In addition, the sample were tested by radioimmunoassay [RIA]. No ELISA modified technique proved valid results that correlated with the standard assay using serum. RIA testing of the blood spots did correlate with the serum results. For antibody assays serum, plasma or the blood spots may be used. Dried serum or plasma spots on filter paper seem to be most suitable for testing the HBsAg