Screening the donated blood supply for Zika virus is most cost-effective during the high mosquito season in Puerto Rico, but no such policy demonstrated cost efficacy in the United States (US), according to results of a study published in the Annals of Internal Medicine.
The epidemic of Zika virus infection spread through the Americas in 2015, and in August 2016, the US Food and Drug Administration (FDA) recommended a universal requirement for individual donation nucleic acid testing of donor blood for Zika virus in the US. During the first year of this screening policy, 257 donations were found to be positive for Zika RNA, and thus intercepted to prevent transmission. In July 2018, the FDA revised the recommendation to restrict to mini-pool screening, with outbreak triggers to revert to universal screening.
For this study, researchers evaluated the clinical and cost efficacy of universal individual donation nucleic acid testing of donor blood via an aggregated model of blood center costs, adverse events, and lifetime economic effects of adverse events as a result of Zika virus transmission from blood transfusion. The study was divided into two 26-week periods based on high vs low mosquito activity, with patients randomly sampled from a representative database. To evaluate cost effectiveness, study investigators chose an alternate willingness-to-pay threshold of $1 million per quality-adjusted life-years gained.
The researchers found that without an intervention, an approximated 242.2 cases (95% CI, 194.9-291.5) of blood transfusion-related infection with Zika virus would have occurred within the first year of screening in Puerto Rico. The alternate willingness-to-pay threshold demonstrated a cost efficacy ratio of $338,597 per quality-adjusted life-years for universal screening compared with no intervention. When compared with other interventions, such as high season mini-pool screening, universal blood screening cost $15.4 million more per quality-adjusted life-years.
In the US, researchers found that an estimated 44.7 cases (95% CI, 32.08-59.08) of Zika virus transmission as a result of blood transfusion would have occurred during the first year of screening without intervention. The positive predictive value of universal screening in the US was 11.6% (95% CI, 7.6%-25.9%).
Further, researchers estimated that mini-pool screening is cost-effective only in donor populations with a >1.2/1000 rate of blood donations, and that escalation to universal screening is cost-effective only in populations with rates >9.8/1000 donations. Notably, assuming that all donations were positive for Zika virus RNA, only donors from Puerto Rico during high mosquito season had a rate of ZIKV-infectious donations that was high enough to make either type of screening cost-effective.
Researchers also demonstrated that mini-pool screening had a positive predictive value >95% even at rates of donations positive for Zika virus infection as low as 1 in 10 million donations. However, universal screening had a positive predictive <25% for rates below 1 in 100 000 donations. Based on the study results, the study investigators concluded that the “July 2018 decision to allow [mini-pool individual donation nucleic acid testing screening] as an alternative to [universal screening] will reduce costs with little to no increase in risk to recipients.”
Russell WA, Stramer SL, Busch MP, Custer B. Screening the blood supple for zika virus in the 50 U.S. States and Puerto Rico: A cost-effectiveness analysis [published online January 8, 2019]. Ann Intern Med. doi:10.7326/M18-2238