Importance of confirmatory testing in donated blood

During the period from January 1995 to January 1996 blood units from 8747 blood donors were screened for blood-borne viruses at King Khalid University Hospital, Riyadh, Saudi Arabia. These tests included HBsAg, antibodies to hepatitis C virus (anti-HCV), antibodies to human immunodeficiency viruses (anti-HIV-1/2). During the same period 1500 blood units were screened for antibodies to human T-cell lymphotropic virus type 1 (anti-HTLV-1). Among the 8747 blood donors, 2.7% were found to be HBsAg-positive on initial screening but 2.2% were confirmed as HBsAg-positive. Regarding HCV, 2.8% were anti-HCV-positive on initial screening but the percentage dropped down to 1.6% on confirmation and only 12 (0.14%) were considered indeterminant by line immunoassay. None of the donors was confirmed anti-HIV- positive but five were diagnosed as indeterminant by western blot. Only four were anti-HTLV- I - positive on initial screening but were diagnosed as indeterminant by western blot. In total, 492 (5.6%) of the blood units tested were reactive for any one of the four viruses on screening but only 327 (3.7%) were confirmed positive. All 492 blood units were not recommended for transfusion. This raises the question of the usefulness of confirmatory testing in blood donation. We believe the confirmation is only important for counseling the donor and a non-reactive result on confirmation should not interfere with the decision of not recommending the blood for transfusion.