Isolation of DNA and RNA

Blood samples for most coagulation tests are collected into 3.8% trisodium citrate in a ratio of 1 part anticoagulant to 9 parts blood. Whole-blood samples for DNA isolation can be stored at −50�C and the DNA prepared at a later stage. A more convenient method requiring less freezer space is to store buffy coats—the interface between the red cells and the plasma that is seen following centrifugation of whole blood. This latter method also allows isolation of the plasma fraction.