Testing donated blood for Zika virus in the United States confirmed just 8 authentic cases and cost nearly $42 million over a period of 15 months, investigators reported online May 10 in the New England Journal of Medicine.
That price did not reflect a commercial price hike, said Paula Saá, PhD, of the American Red Cross in Gaithersburg, MD, and her associates. Furthermore, more than half of the Zika cases had a low viral level that might not be infectious.
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Among more than 4 million screened donations, 9% were tested in pools. All pooled tests were negative. The other 3.9 million donations were screened individually. Only 160 were positive, and just 6 were confirmed positive on repeat TMA. Two of these six confirmed positives also were RNA-positive on reverse transcription polymerase chain reaction, while two were equivocal and two were negative. The positive and equivocal donations were negative for Zika immunoglobulin M on enzyme-linked immunosorbent assay, which indicated acute infections. The RNA-negative infections were IgM-positive, indicating prior infections.
Three more donations were initially positive on TMA, were negative on repeat TMA, and were IgM-positive, bringing the total case count to nine. Among these, two donors had been infected in Florida, six had traveled to Zika-endemic areas, and one had received an experimental Zika vaccine, according to the researchers.
For each detection of authentic Zika virus RNA infection in U.S.-donated blood, testing had cost $5.3 million, they concluded. They called the current FDA recommendation to individually screen all U.S. blood donations for Zika virus “low-yield” and “high cost.” Of three acute infections with enough sample left for pooled testing, all were positive, they noted.
The American Red Cross and Grifols Diagnostic Solutions provided funding. Dr. Saá disclosed research support from Grifols, which makes the TMA test used in the study. She had no other conflicts of interest.
SOURCE: Saá P et al. New Engl J Med. 2018;378:1778-88.