Costs, consequences, and cost-effectiveness of strategies for Babesia microti donor screening of the US blood supply.

Abstract

Babesia microti is regarded as the foremost infectious risk to the US blood supply for which a regulatory-approved screening test is unavailable. More than 160 cases of transfusion-transmitted Babesia microti (TTB) have been reported to date, yet there is little consensus regarding a mitigation strategy. This study sought to assess the cost-utility of donation screening by mode of testing (immunofluorescence assay, enzyme-linked immunosorbent assay [ELISA], polymerase chain reaction [PCR], and combinations thereof) as well as extent of geographic inclusion (4-state, 7-state, 20-state, or national screening). A discrete-time Markov cohort model to simulate the outcomes of B. microti infection and survival of the transfused population was developed. Seroprevalence was estimated by extrapolating babesiosis claims from the Centers for Medicaid and Medicare Services and reports to the Centers for Disease Control and Prevention. Test performance was estimated from clinical diagnostics and limited donor screening studies, while transmissibility was estimated as a weighted average of three studies. Results are reported as the cost per quality-adjusted life-year (QALY) for each strategy compared to no screening. Given model inputs, 4-state and 7-state ELISA in combination with PCR would cost $5.2 million and $6.6 million/QALY, respectively. Cost-effectiveness for 20-state and national screening strategies were less favorable. Targeted screening in states with the highest seroprevalence of infection is likely to exceed an implicit threshold of $1 million/QALY often used in blood safety. However, the proportion of donor-seronegative parasitemia, transmissibility, and clinical outcomes resulting from TTB are uncertain.