Abstract: A sample is prepared from blood in a manner which makes it possible to further analyze proteins in the sample, e.g. to detect prions in the sample. Blood is extracted, allowed to clot and subjected to separation processing (e.g. centrifugation) to obtain serum. The serum is treated with a complexing agent which agent binds prions in the sample forming an agent/protein complex which makes it possible to concentrate the complex. Concentration of the complex results in a sample which can be successfully analyzed, e.g. assayed using a range of different types of assay methodologies for detecting prions.

Abstract: A method of concentrating a disease-related conformation of a protein such as the PrP.sup.Sc in a sample is disclosed. The method comprises liquefying the sample and adding a complexing agent such as phosphotungstic acid (PTA) which complexes preferentially or exclusively with the PrP.sup.Sc. After the complex is formed the composition is centrifuged until the complex settles at the bottom. Thereafter, the supernatant is poured away. The remaining pellet may be resuspended in an aqueous solution containing a protease inhibitor for storage. The PTA stains the PrP.sup.Sc making the resulting concentrated PrP.sup.Sc susceptible to further analysis, making it possible to quickly and efficiently determine the presence of PrP.sup.Sc and its concentration in a sample. The method can be used to render a sample non-infectious by removing all or substantial of the infectious form of a protein from a sample.

Abstract: An assay method is disclosed which makes it possible to determine the presence of a diseased related conformation of a protein (e.g., PrP.sup.Sc) in a sample. A sample is divided into two portions and the first portion is cross-linked to a first solid support and then contacted with a labelled antibody which binds to a non-disease form of the protein with a higher degree of affinity (e.g, 4 to 30 fold higher) than to the disease form of the protein. The second portion is treated in a manner which causes any disease form of the protein to change conformation to a form with a higher binding affinity for the labelled antibody. The treated second portion is then bound to a second solid support and contacted with labelled antibody. The level of labelled antibody binding to a protein in the first and second portions is determined and the amounts measured in each are compared.