title: Investigational screening for Babesia microti in a large repository of blood donor samples from nonendemic and endemic areas of the United States.
abstract: BACKGROUND
  Babesia microti, a transfusion-transmissible intraerythrocytic parasite, is increasing in frequency in the United States with no available FDA-licensed donor screening assay. We utilized investigational arrayed fluorescence immunoassay (AFIA) and polymerase chain reaction (PCR) to detect B. microti antibodies and DNA in blood donors.
  
  
  METHODS
  AFIA and real-time PCR were performed on frozen paired EDTA plasma (AFIA) and EDTA whole blood (PCR) samples collected from May to September 2010 to 2011 in nonendemic (Arizona [AZ] and Oklahoma [OK]), moderately endemic (Minnesota [MN] and Wisconsin [WI]), and highly endemic (Connecticut [CT] and Massachusetts [MA]) areas of the United States. AFIA utilized B. microti piroplasm as an antigen substrate; PCR primers and probes targeted the B. microti 18S ribosomal RNA gene. Data from AZ and OK were used to calculate specificity. All AFIA- or PCR-positive or -inconclusive donors were deferred, notified, and invited to participate in a follow-up study involving repeat testing and a demographic and risk-factor questionnaire. Recipient tracing was performed for any cellular component transfused at index, at subsequent donation, or within the prior 12 months.
  
  
  RESULTS
  Testing of 13,269 paired samples included 4022 from AZ and OK, 4167 from MN and WI, and 5080 from CT and MA. B. microti antibody and/or DNA prevalences were 0.025% (95% confidence interval [CI], 0.00%-0.14%), 0.12% (95% CI, 0.04%-0.28%), and 0.75% (95% CI, 0.53%-1.03%) in the nonendemic, mid-endemic, and high-endemic regions, respectively. Specificities were 99.95% (95% CI, 99.82%-99.99%) at a 1-in-64 AFIA cutoff and 99.98% (95% CI, 99.86%-100.00%) at a 1-in-128 cutoff.
  
  
  CONCLUSIONS
  B. microti prevalence followed expected geographical patterns. Screening was feasible with a performance comparable or superior to other infectious disease blood donor screening assays.
authors.affiliation: Scientific Support Office, American Red Cross, Gaithersburg, Maryland.
authors.forename: Erin D
authors.initials: ED
authors.lastname: Moritz
authors.forename: Colleen S
authors.initials: CS
authors.lastname: Winton
authors.forename: Stephanie T
authors.initials: ST
authors.lastname: Johnson
authors.forename: David E
authors.initials: DE
authors.lastname: Krysztof
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Townsend
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Foster
authors.forename: Patricia
authors.initials: P
authors.lastname: Devine
authors.forename: Philip
authors.initials: P
authors.lastname: Molloy
authors.forename: Edward
authors.initials: E
authors.lastname: Brissette
authors.forename: Victor P
authors.initials: VP
authors.lastname: Berardi
authors.forename: Susan L
authors.initials: SL
authors.lastname: Stramer
mesh_terms: D000913:Antibodies, Protozoan / Q000097:blood; D041001:Babesia microti / Q000235:genetics / Q000276:immunology / Q000472:pathogenicity*; D001782:Blood Donors / Q000706:statistics & numerical data*; D016054:DNA, Protozoan / Q000097:blood; D006801:Humans; D060888:Real-Time Polymerase Chain Reaction; D014481:United States
chemical_list: D000913:Antibodies, Protozoan; D016054:DNA, Protozoan