the present invention deals with a method of preparing nucleic acids , particularly rna , from a whole blood sample . the nucleic acids purified by the method of the invention are particularly suited for detection of nucleic acid marker molecules . preferred are markers for the diagnosis of transmissible spongiform encephalopathy . such diagnosis is based on the detection , by means of real - time pcr , of certain mrnas of the tse - infected organism . said mrnas specifically originate as splicing variants and are isolated from whole blood by the method of the invention .