Paper discs impregnated with capillary blood. A sampling technique for immunoassays by means of DIG-ELISA and DIG-TIA.

A modification of the diffusion-in-gel enzyme-linked immunosorbent assay (DIG-ELISA) and the diffusion-in-gel thin layer immunoassay (DIG-TIA) using paper discs impregnated with blood or serum as source of diffusion is described. Using a BSA-anti-BSA model system the suitability of this sampling and assaying technique for simple and accurate quantitation of antibodies has been demonstrated. Paper discs impregnated with blood or serum and subsequently dried could be stored at temperatures between +4 degrees C and +37 degrees C for at least six weeks without significant loss of antibody activity. Application of paper disc DIG-ELISA was exemplified by assaying anti-BSA antibodies in rabbits immunized with BSA as well as antibodies against both soluble egg antigen and adult worm extract in mice experimentally infected with Schistosoma mansoni cercariae. The simplicity and good reproducibility of this technique should make it an attractive alternative in serological screening of large population groups. Definite advantages of this technique are the possibilities to analyse quantitatively antibodies in capillary blood, rather than serum from venous blood samples, and to store sampled material for a considerable time even under such climatic conditions as often prevail in tropical countries.