Q.What is the current protocol for testing donors or organs before a transplant is conducted?
A. Organ donors are screened to identify infectious risks on the basis of national organ-procurement standards. Screening of all organ donors with WNV NAT is not currently required or routinely performed due to:

(1) the length of turnaround time to obtain WNV nucleic acid-amplification test (NAT) testing, and

(2) the unproven test performance in the organ-donation setting. National guidelines for organ-donor screening are continuously reevaluated by the Health Resources and Services Administration in consultation with FDA, CDC, and organ-procurement organizations.

(a) Time is a critical factor in organ donation; one analysis suggested that WNV NAT screening might result in a net loss of years of life among certain types of potential transplant recipients because screening might exclude healthy donors from an already limited donor pool. The time pressure to test and process donated blood is not as extreme.

(b) Additionally, NAT has not yet been proven as an effective test in the organ-donation setting—it is not known at this time that it would prove as useful as it has in identifying blood donations that pose a risk.

(c) It has been learned through limited retrospective studies that transfused viremic donations did not transmit WNV infection if IgM antibody was present, and investigation of all 30 cases of WNV transmitted by blood transfusion documented to date indicated that the donors’ viremias can be of low titer and that all resulted from IgM antibody-negative donations. This instance of organ-transplant-associated WNV transmission suggests that transmission through solid organ transplantation can occur from donors with IgM and IgG antibodies and without detectable nucleic acid by PCR in their serum. Experimental evidence in humans and animals suggests that WNV might persist in organs after clearance of viremia (e.g.., when virus is no longer circulating in the bloodstream.) This would present a different scenario, requiring different testing, than the case of NAT testing of donated blood.

Guidance related to donated organs, and the use of screening and diagnostic tests for West Nile virus was issued January 9, 2004 and is posted on the website of the Organ Procurement and Transplantation Network.