Today we will be discussing the relative efficacy of different screening strategies for the hepatitis C virus (or HCV). Similar to other viral infections, HCV has a pre-serological “window period,” where donated blood may contain infectious particles which are detectible by a nucleic acid test, but does not have detectable antibodies to the virus. Blood products are screened for HCV using an immunoassay to detect antibodies and also a nucleic acid test (or NAT). The NAT test is performed by mini-pooling donor samples or performing individual donor tests, called ID-NAT.
Two recent studies published in TRANSFUSION examined the efficacy of different testing scenarios for HCV. In a multi-country study, 21 blood organizations screened over 10 million samples using ID-NAT and an anti-HCV immunoassay.
Dr. Bruhn, who led the study summarizes their findings:
“ID-NAT with or without serologic testing showed higher efficacy than either mini-pool NAT or combo assays. We estimate that 99.2%, 98.5% and 93.2% of infectious donations would be interdicted by ID-NAT, mini-pool NAT, and a combo assay, respectively. The incremental efficacy of anti-HCV testing when ID-NAT screening is performed is minimal.”
A second study screened almost 120,000 donations. Researchers examined HCV viral loads in three stages of infection. They focused on antibody positive samples from donors with probable resolved infections without detectable RNA by ID-NAT.
Dr. Lelie, the lead investigator, explains their findings for samples with probable resolved infections:
“We used those donors to perform replicate tests on their plasma to confirm that 99% of these individuals had indeed eradicated their infection. We only found 2 of 175 donors with probable resolved infection that had extreme low viral load below 1-2 copies/milliliter with only few of 25 replicate ID-NAT tests were reactive.”
The study team then used their results to estimate the risk of HCV transfusion-transmitted infections to be 0.028% if samples were ID-NAT negative and serologically positive. Therefore, they concluded that serological testing provides minimal benefits. If only serological testing is performed, the risk of infection increases 21- to 34-fold.
Mr. Kiely, who wrote an accompanying editorial summarizes:
“These two articles very much put the challenge on the blood services to consider cost-effectiveness, and they provide some very interesting data and extensive data…that actually demonstrate that…simply using the hepatitis C NAT screen without the antibody screening probably in most jurisdictions results in some substantial cost-savings without any significant loss in terms sensitivity and the ability to detect infectious donors.”
We’ll be back with another edition of Transfusion News on June 30. Thanks for joining us.
1. Bruhn R, Lelie N, Busch M, Kleinman S, the International NATSG. Relative efficacy of nucleic acid amplification testing and serologic screening in preventing hepatitis C virus transmission risk in seven international regions. Transfusion 2015. doi: 10.1111/trf.13024.
2. El Ekiaby M, Moftah F, Goubran H, van Drimmelen H, LaPerche S, Kleinman S, Busch M, Lelie N. Viremia levels in hepatitis C infection among Egyptian blood donors and implications for transmission risk with different screening scenarios. Transfusion 2015. doi: 10.1111/trf.13061.
3. Kiely P. Screening blood donors for hepatitis C virus–the challenge to consider cost-effectiveness. Transfusion 2015.