Universal Screening of Donated Blood for Zika Not Cost-Effective

Veronica Hackethal, MD

January 07, 2019

A new study has estimated that nationwide universal screening for Zika virus among donated blood was not cost-effective during the first year of the policy in any of the 50 states, including Washington, DC. 

Results were published online today in the Annals of Internal Medicine.

The study also found that certain screening strategies may be cost-effective in Puerto Rico, where transmission of Zika is higher than in the 50 states. But screening was cost-effective only during the high mosquito season. Moreover, cost-effectiveness is expected to decline during periods when blood donations are less likely to be infected with Zika.  

As a result of the findings, the authors had a potentially controversial suggestion: downgrading screening requirements for Zika in donor blood.

"Unless the number of ZIKV [Zika virus]-positive donations interdicted increases substantially, further reduction of screening requirements should be considered," lead author W. Alton Russell, MS, Stanford University, Stanford, California, and colleagues write.

In August 2016, the US started universal screening of donated blood for Zika virus using the individual nucleic acid testing (ID-NAT) test.

However, testing came at a high cost: an estimated $137 million annually in the 50 states and Washington, DC, according to one study. That, combined with declining rates of Zika infection as the epidemic came under control, may have raised questions about the cost-effectiveness of universal testing.

In 2018, the US Food and Drug Administration (FDA) issued revised recommendations and allowed the lower cost screening test, known as the mini-pool nucleic acid testing (MP-NAT), during local outbreaks or those brought into the US by travel.  Whether or not the MP-NAT is cost-effective is also open to question.

To evaluate the cost-effectiveness of universal screening of donated blood for Zika during the first year after the FDA's 2016 policy took effect, researchers conducted a simulation study for a range of screening strategies. These included universal MP-NAT, ID-NAT just for women of childbearing age, and various combinations of ID-NAT and MP-NAT targeted at geographic locations with relatively high rates of transmission (or travelers coming from such areas).

Researchers evaluated a random sample of transfusion recipients, as estimated from national testing results (5 million in the 50 states and 31,000 in Puerto Rico in 2016).

The analyses evaluated costs, clinical outcomes, and potential harms of receiving Zika-infected blood, including asymptomatic infection, mild febrile illness, Guillain-Barré syndrome, and birth defects. They also looked at total medical costs, productivity loss due to illness or death, and loss of quality-adjusted life-years (QALYs).

At a cost effectiveness threshold defined as $1 million per QALY gained, the ID-NAT strategy was not effective in the 50 US states. Using the ID-NAT for universal screening, as recommended by the FDA, would cost $341 million per QALY saved, vs no screening. The results suggest no screening may be preferred, according to the authors.

In contrast, screening was effective in Puerto Rico, but only for MP-NAT during the high mosquito season (April through September). Researchers estimated that testing exclusively with MP-NAT during the high mosquito season would result in a savings of $81,123 per QALY (95% confidence interval [CI], -$49,138 to $978,242 per QALY).

For Puerto Rico, the next most cost-effective strategy was ID-NAT during the high mosquito season and MP-NAT in the low season. Compared to these strategies, universal year-round ID-NAT would cost $15.4 million more per QALY gained (95% CI, $2.2 million to $95.2 million per QALY).

Sensitivity analyses showed that MP-NAT during the high mosquito season was cost-effective in Puerto Rico in 64% of analyses. In the 50 states, no intervention was cost-effective in 99.99% of sensitivity analyses.

Further analyses showed that not screening for Zika in donated blood would result in an estimated one case of Guillain-Barré syndrome every 16 years and one case of congenital Zika syndrome every 33 years in Puerto Rico. In the 50 states, not screening would result in one case of Guillain-Barré every 84 years, and one case of congenital Zika syndrome every 176 years. The analyses assumed that Zika outbreaks did not occur and infection rates among donated blood remained the same.  

In an accompanying editorial, Katherine Ellingson, PhD, University of Arizona, Tucson, and Matthew Kuehnert, MD, of MTF Biologics in Edison, New Jersey, write that the study is "well-executed" and may provide an opportunity to discuss trade-offs, given evolving yet still limited knowledge about Zika.

Past experience with transmission of HIV and hepatitis C via infected blood products has made the "precautionary principle" central to protecting the blood supply, they write.

"Because this principle can promote the expectation of zero risk, policymakers must consider how various options for blood screening foster or damage public trust in the face of uncertain risk," they write.

They went on to note that the results of this study should be interpreted in light of the tendency for mosquito-borne infections like Zika to cause episodic or seasonal outbreaks, and to expand to new areas. Nevertheless, they also suggested that a change in screening requirements may be in order.

"Current screening policies are extraordinarily costly per QALY saved, which suggests the need for a new paradigm in preventing TTIs [transfusion-transmitted infections]," they write.

The study was funded by Vitalant Research Institute. One or more authors reports personal fees, laboratory support/funding, speaker fees, and/or grants from one or more of the following: Terumo BCT, Grifols, Roche Diagnostics, Abbott Laboratories, Cerus, and/or Macopharma. The editorialists have disclosed no relevant financial relationships.

Ann Intern Med. Published online January 7, 2019. Abstract, Editorial

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