Risk of prion disease transmission from ocular donor tissue transplantation

Recent new reports of possible iatrogenic transmission of Creutzfeldt-Jakob disease (CJD) in Europe have prompted renewed scrutiny of current Eye Bank Association of America criteria for evaluation of potential corneal donors in this country. A prior study evaluated the risk of CJD occurring in U.S. corneal donors by using data to 1994. This report updates these data, analyses the risk by using data to 1997, and predicts potential risk into the next decade.

EBAA data inclusive through 1997 were reviewed and correlated with incidence figures for CJD in the United States as provided by the Communicable Disease Center in Atlanta.

The annual incidence of CJD has remained stable at 1 case per million population. Thus approximately 270 new cases of CJD would be expected to occur each year in the United States. From this, the calculated risk of a prion-infected corneal donor appearing in the donor pool is 0.045 cases per year. If the data are corrected for age (90% of CJD patients are older than 60 years) and for possible infected but asymptomatic CJD patients (prevalence, 70 cases per million), at worst, 2.12 cases per year would appear for potential corneal donation (0.005% of all donors). Whereas donors completely without any neurologic symptoms cannot be screened by using any currently available laboratory method, those with a characteristic quadrate clinical prodrome including cognitive changes, speech abnormalities, cerebellar findings, and myoclonus could all be potentially excluded by using tightened medical record and historical screening criteria. Although no cases of bovine spongiform encephalopathy (mad-cow disease) or new variant CJD have been reported in the United States, if such should occur, only 4.2 cases of CJD would be expected in potential donors each year (0.009% of all donors). Tightening of exclusionary queries would significantly reduce the risk of even this number of patients appearing for corneal donation.

Historical queries of potential corneal donors should be tightened to assure exclusion of donors with early neurologic alterations. Any patient undergoing autopsy for evaluation of possible central nervous system (CNS) disease should be absolutely excluded. With this approach, the risk of inclusion of CJD-infected transplant tissues derived from ocular sources is very small, and all previously reported cases would have been prospectively excluded from surgical use. Clearly, the benefits of corneal transplantation in the overall population continue significantly to outweigh the risks of transmission of prion disease.