BACKGROUNDBlood transfusion safety is based on reliable donor screening for transmissible infections such as the hepatitis C virus (HCV) infection.STUDY DESIGN AND METHODSA novel HCV core–specific antibody was assayed on random single donations from 2007 first‐time blood donors who tested negative for anti‐HCV and HCV RNA on routine screening. Sample collection broke the code between donations and donors for ethical reasons.RESULTSForty‐two donations (2.1%) displayed reactivity in the novel test. The specificity of the reactivity was evaluated by a peptide inhibition assay, and testing against additional nonoverlapping HCV core peptide epitopes and other HCV antigens was performed on these samples. Six donations (14.3%; 0.30% from the total) were considered to contain anti‐HCV after such supplemental testing. HCV RNA detection was also performed in peripheral blood mononuclear cells (PBMNCs) and serum or plasma samples from reactive donors after virus concentration by ultracentrifugation. HCV RNA tested negative in all PBMNCs samples, and a very low amount of viral genome was detected in serum or plasma concentrates from three anti‐HCV core–reactive donors (7.1%) but not among concentrates from 100 randomly selected nonreactive donors. Sequencing of these polymerase chain reaction products revealed differences between the isolates that excluded partially sample contamination from a common source.CONCLUSIONThese findings argue in favor of an ongoing occult HCV infection among these blood donors and account for some rather low, but perhaps not negligible, infection risk for such donations. Future studies involving larger samples of donations from traceable donors would enlighten the significance of these findings for the viral safety of the blood supply.

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