November 14, 2014
Babesia microti is currently the most commonly transfusion-transmitted infectious agent that results in clinical disease and fatality in recipients. More than 160 cases of transfusion-transmitted babesia (TTB) have been documented in the United States, contributing to at least 28 associated deaths in the 30 years from 1979 to 2009. In 2009, the AABB Transfusion Transmitted Diseases Committee identified this agent as one of the three highest priority infectious agents for development of an intervention.
Tick-borne babesiosis is a regional disease. There are highly endemic states (and highly endemic areas within these states), moderately endemic states, and other states that report few to no babesiosis cases. Currently, most cases in the United States occur in New England and the upper Midwest; however, the geographic range of B. microti is expanding.
In highly endemic areas, the current per unit risk of transfusion-transmitted babesiosis – in the absence of donor screening – is in the range of 1 in 20,000 to 1 in 30,000 per transfused red blood cell unit. This is approximately 30- to 50-fold higher than the current residual per unit risk of transmitting HIV, HBV or HCV by transfusion.
In these highly endemic areas, the application of a babesia testing algorithm currently approved by the Food and Drug Administration (FDA) under IND has been demonstrated to significantly reduce risk. To date, there have been no cases transmitted by screened blood.
Based on these facts, AABB strongly urges FDA to review expeditiously licensure applications for B. microti donor screening assays that are or will be submitted to the agency. AABB supports the use of a licensed B. microti screening assay (or assays) in endemic areas. We recognize that a definition of such areas is still needed, as is a mechanism to ensure effective implementation of licensed assay(s).
In determining whether testing should be performed in non-endemic areas, incremental safety gains must be balanced against appropriate use of limited health care dollars and resources. This issue needs further public debate, informed by a careful review of existing data as well as cost-effectiveness analyses using the data collected under IND.