TABLE 1.

Comparison of concentrations of B. burgdorferi in plasma and serum

Replicate no.a	Concnb in:		Plasma/serum concn ratio
	Plasma	Serum
1	4.000	0.072	55.56
2	1.400	0.040	35.00
3	1.300	0.056	23.21
4	1.400	0.032	43.75
5	1.500	0.012	125.00
6	1.500	0.012	125.00
7	0.960	0.008	120.00
8	0.580	0.012	48.33
9	3.300	0.160	20.63
10	4.100	0.100	41.00
11	0.150	0.024	6.25
12	0.100	0.052	1.92

^aEach replicate represents paired serum and plasma samples from healthy volunteers seronegative for antibody to B. burgdorferi. Freshly collected blood, both with and without the anticoagulant EDTA, was spiked with the same number of B. burgdorferi microorganisms. 

^bConcentrations are expressed as numbers of B. burgdorferi organisms (10⁸) per milliliter.