Screening Blood Donations for Zika Has Low Yield, High Cost

Marcia Frellick

May 09, 2018

In the first 15 months after they began screening blood donations for the Zika virus (ZIKV), the American Red Cross identified just eight true positives, at a cost of $5.3 million each, according to data published online today in the New England Journal Medicine. The findings raise questions about whether screening blood donations in the United States for ZIKV should continue in the same way given the high cost and low yield of the screening.

In 2016, the US Food and Drug Administration (FDA) recommended individual-unit nucleic acid testing for all blood donations to minimize the risk for transmission of ZIKV through transfusions.

If ZIKV screening follows current FDA guidance, the projected cost per year for national screening is estimated to be $137 million (range, $109 million to $167 million), Paula Saa, PhD, from the American Red Cross Scientific Affairs division in Gaithersburg, Maryland, and colleagues write.

More Than 4 Million Donations Examined

Saa and colleagues analyzed ZIKV screening data from 4,325,889 blood donations in the United States from a 15-month period in 2016 and 2017. She told Medscape Medical News there were nine positive donations identified by nucleic acid testing, with eight donors having been bitten by a mosquito and one having received a ZIKV vaccine, for a rate of 1 per 480,654 donations screened.

Saa and colleagues write, "Among the nine donors whose blood was confirmed as ZIKV-positive, only four had acute infection (i.e., were [immunoglobulin M] IgM-negative); among these four donors, all three with adequate sample volumes for testing also tested positive on minipool [transcription-mediated amplification]." That finding suggests screening costs might be lowered by pooling samples without substantially reducing screening accuracy.

The FDA's decision in 2016 was part of a rapid response in light of the large proportion of asymptomatic cases, large numbers of asymptomatic travelers returning from ZIKV-active areas, reports of ZIKV infections likely coming from transfusions, and the devastating effects of infection.

In an accompanying editorial, Evan M. Bloch, MBChB, from Johns Hopkins School of Medicine in Baltimore, Maryland, and colleagues say the reasons for starting the testing should not be second-guessed: "A similar proactive response to HIV could have resulted in a reality very different from the pandemic that unfolded in the 1980s," they write.

However, given current evidence, they say, risk-based approaches need to be regularly evaluated to determine whether screening blood donations should be continued, modified, or stopped.

"The current U.S. strategy for ZIKV screening comes at a cost with an unclear gain," Bloch and colleagues write. "Although concerns about blood safety are vital, is it appropriate and possible to reverse blood-donation screening for ZIKV in the United States in light of emerging data?"

They suggest some points to consider. One, they say, is that they are unaware of any case of clinical ZIKV infection that has been linked to a transfusion.

"The four reported cases of transfusion-transmitted ZIKV infection were based solely on laboratory evidence; of the three living transfusion recipients, none displayed any clinical sign of ZIKV infection," they write.

Also, even if there were such a clinical risk to transfusion recipients, much of the risk applies to fetuses, the authors write. "At least in the United States, receiving a transfusion while pregnant is uncommon (0.24% to 0.46% of pregnancies), which suggests that national screening is unnecessary or alternatively, that compiling a limited inventory of ZIKV-screened blood for use in high-risk recipients (e.g., women receiving intrauterine transfusion) could be considered."

A third consideration is that ZIKV is rare among blood donors in the United States, and most cases would have been identified by questions as to whether the person had traveled to a country where the virus is highly endemic.

The editorialists suggest that the money devoted to Zika blood screening may be coming at the expense of diseases with bigger infectious risks. They note that more than 200 cases of babesiosis linked to mortality, for instance, have been reported to be transmitted through transfusion in the United States but screening has not been mandated.

Meanwhile, Zika incidence has decreased substantially.

"In the continental United States, the reported number of locally acquired, mosquito-borne cases of ZIKV infection decreased from 226 in 2016 to 2 in 2017," the editorialists write. "At the time of this writing, there are no active areas of ZIKV transmission, and donations that are positive for ZIKV RNA are rare."

However, Bloch and colleagues also say there may be reasons to defer a decision on whether to change the current policy around screening because of key research currently under way regarding blood donations and Zika.

"Data from these efforts, which are likely to be available in the near future, would strengthen any policy decisions," they write.

Saa reports other support from Grifols during the conduct of the study. Coauthors also report other support from Grifols during the conduct of the study and personal fees from Grifols outside the submitted work, and personal fees and other support from Roche, Abbott Laboratories, and Cerus. Two coauthors have a patent titled "Compositions and Methods for Detecting Zika Virus Nucleic Acid" pending.

Bloch reports grants from Terumo BCT outside the submitted work. Several coauthors of the editorial report personal fees and/or nonfinancial support from one or more of the following entities: Grifols, Terumo BCT, Lakewood Colorado, Merck KGaA, IQVIA (Formerly Quintiles), Novartis, Ortho Clinical Diagnostics, and Quotient. A coauthor serves as an unpaid member of Canadian Blood Services' Scientific Research and Advisory Committee.

N Engl J Med. Published online May 9, 2018. Full textEditorial

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