A laboratory-based blood donor-screening program for Babesia microti
has been developed and implemented to reduce transfusion-transmitted babesiosis (TTB).
Selective B. microti
donor screening was performed using real-time polymerase chain reaction (PCR) and indirect immunofluorescence assay (IFA) to reduce the incidence of TTB in neonates and pediatric sickle cell and thalassemia patients.
A team of scientists collaborating with the Rhode Island Blood Center (Providence, RI, USA) screened 2,113 units of blood from 1,783 eligible donors for the presence of B. microti
between July 8, 2010, and June 30, 2011. B. microti
antibody testing was performed at Imugen, Inc. (Norwood, MA, USA) using an IFA method with additional modifications to improve sensitivity and specificity and to facilitate future high-throughput screening. PCR was carried out employing primers and probes targeting the B. microti
18S ribosomal ribonucleic acid (RNA) gene and was also performed at Imugen, Inc., using a highly sensitive and specific real-time fast PCR method approved by the US Food and Drug Administration (FDA; Silver Springs, MD, USA).
There were 2,113 units tested with 2,086 negative results, 26 positive IFA results (1.23%), and one indeterminate PCR result (0.05%). No reported case of TTB occurred with any B. microti
–screened unit transfused to the targeted patients (0/787 units) or to any patient who received the screened units (0/2,086 units). Before screening, there were seven cases of TTB in neonates, sickle cell, and thalassemia patients from 6,500 unscreened units (one case/929 units) and 24 cases in the total transfused population from 496,545 units distributed (one case/20,686 units).
The authors concluded that the problem of donor loss due to laboratory screening would be outweighed by the benefit of increased protection such screening provides. After three neonatal TTB cases occurred from one infected donor in 2006, the hospital began transfusing one red blood cell unit per patient with up to 10 aliquots per unit. The hospital with screening could safely use one unit for many neonates. The prescreening TTB incidence data of 1 in 995 aliquots compared to the postscreening TTB incidence of 0 in 545 aliquots are promising. Therefore, donor testing mitigated TTB in a highly vulnerable recipient population.
Babesia microti, the most common cause of human babesiosis, is also the most frequently reported transfusion-transmitted microbial pathogen in the United States with 159 cases of transfusion-associated infection reported during 1979 to 2009, involving 19 states. Rhode Island is highly endemic for babesiosis with rates of reported babesiosis exceeding 90 cases per 100,000 in 2008. The study was published in the July 2012 edition of the journal Transfusion.
Rhode Island Blood Center
US Food and Drug Administration