Table 2.

Summary of blood donor B. microti screening study results.

Study	Regions screened		No. donors tested	Serologic assay	No. seropositive		No. PCR positive	No. PCR and seropositive	Specificity (95% CI)*
	Endemic	Non-endemic			Endemic	Non-endemic	Endemic	Endemic
Young, 2012 [23]	RI	N/A	2,113	IFA (AFIA)	26/2,113 (1.23%)	N/A	0	0/26 (0%)	N/A
Moritz, 2014 [34]	CT, MA	AZ, OK	13,269	IFA (AFIA)	38/5,080 (0.75%)	3/4,022 (0.075%)	5/5,080 (0.1%)	5/38 (13%)	99.95% (99.82–99.99)
Levin, 2014 [45]	NY	AZ	15,000	ELISA	46/5,000 (0.92%)	8/5,000 (0.16%)	1/5,000 (0.02%)	1/46 (2.2%)	NA
Levin, 2016 [35]	NY	NM	26,703	ELISA	38/13,757 (0.28%)	11/8,363 (0.13%)	8/13,757 (0.06%)	8/38 (21%)	99.93% (99.84–99.97)

^*after exclusion of confirmed positives

Note: The sensitivity of the IFA (AFIA) assay for detection of PCR-positive patients with symptoms of babesiosis was reported as 81.6%, with non-detected cases presumed to be in the window period[34]. The sensitivity of the ELISA assay for PCR or blood smear positive patients with symptoms of babesiosis was 78.3%[35]. The two methods were statistically equivalent in sensitivity.