Table 2.

Reactivity of samples initially scored in the gray zone in the B . microti EIA

Region	EIA initially gray zone	EIA reactive or gray zone upon retest	IFA reactive	PCR positive	Blood smear positive
High-risk endemic (n = 5000)	19	14	1	0	0
Lower-risk endemic (n = 5000)	14	13	0	0	0
Nonendemic (n = 5000)	17	12	0	0	0

Numbers of samples in each category are shown.

The single IFA reactive sample in this table exhibited an estimated IFA titer of 1:64 for IgG, and was scored in the EIA gray zone initially and upon retest. An additional sample not included in Tables1 and 2 was initially EIA reactive but in the gray zone on retesting.