The impact of Creutzfeldt-Jakob disease and variant Creutzfeldt-Jakob disease on plasma safety.

Although the true risk of transmitting (classical) Creutzfeld-Jakob Disease (CJD) and variant CJD (vCJD) via transfusion is likely very minimal, a review of prions and the impact of these associated prion diseases is timely because of their current effect on safety policies in the blood-plasma industry. Various types of human and animal prion diseases are outlined and reviewed, with emphasis on the importance of cross-species transmission as is relevant for vCJD. Review of the prion theory focuses on the relationship of prions to disease pathophysiology, prion resistance to protein modification, and potential prion transmission. Causes (with emphasis on iatrogenic CJD) and diagnosis of clinical CJD are described and contrasted with the same for vCJD. The origin of vCJD, the pathophysiologic questions surrounding this condition, and the latest diagnostic tests and research are also reviewed. Comparison of transmission feasibility versus actual transmission of CJD or vCJD by blood or blood products is then explored. Reasons for the discrepancy between theoretic and actual transmission for CJD and the body of evidence provided by look-back studies are examined. When compared with CJD, reasons are provided for the higher theoretic risk of transmitting vCJD by blood products. Studies evaluating transmission by blood products in animals are considered. Transfusion practices that include European and US criteria to prevent vCJD through blood products are reviewed. This includes the debate surrounding product leukoreduction, deferral of donors at high risk either for exposure to vCJD or for contracting CJD, targeted elimination of donor plasma, and how some policies may have contributed to product shortages.