Molecular Assays Evaluated for Influenza in Blood Donors

Several influenza RNA amplification assays, including transcription-mediated amplification (TMA) and two reverse-transcription polymerase chain reaction (RT-PCR) assays were evaluated and used to test donor samples.

Scientists at the Blood Systems Research Institute (San Francisco, CA, USA) collaborating with other institutes, retrospectively tested samples from 478 subjects drawn at sites with high influenza activity. They collected prospective samples from 1,004 blood donors who called their donation center within three days of donation complaining of influenza-like illness (ILI). The plasma collected on the day of donation for these subjects was tested.

A number of different influenza RNA detection assays were evaluated prior to testing donor samples, all of which were previously shown to detect commonly circulating contemporary influenza viruses. The MGB Alert system (Epoch Biosciences; Bothell, WA, USA) uses RNA extraction followed by RT-PCR. The Prodesse ProFlu-1 assay (Gen-Probe, San Diego, CA, USA) uses RNA extraction followed by a TaqMan-based, real-time RT-PCR amplification targeting the influenza A matrix gene. Transcription-mediated amplification, also from Gen-Probe, uses a target-capture probe for influenza A matrix gene during RNA extraction followed by isothermal amplification using bacteriophage T7 RNA polymerase and Moloney murine leukemia virus reverse transcriptase. The assays were validated on spiked samples and an animal model.

Of the repository samples, two of 478 plasma samples were initially reactive, but were not repeat reactive by influenza TMA. Of blood donors reporting ILI symptoms after donation, only one of 1,004 samples was TMA initially reactive, but was not repeat reactive, while all samples were nonreactive by RT-PCR testing. The authors reported that they failed to detect influenza A viremia using very sensitive tests in blood samples from donors collected during periods of high influenza transmission in the community, with the majority of the tested donors reporting symptoms of influenza-like illness. The preponderance of evidence from this and other studies thus suggests that influenza viremia is at most an exceedingly rare event in blood donors, who are healthy at the time of donation, and that influenza viremia only occurs in subjects with moderate to severe disease. The study was published on March 15, 2012, in the Journal of Infectious Diseases.

Related Links:
Blood Systems Research Institute
Epoch Biosciences
Gen-Probe