Table 1.

Crossing thresholds and interpretations of 15 samples when pooled with various numbers of negative samples.

Sample number, concentration, initial Ct with E and N2 Targets			Repeat result			Pool of 3 samples			Pool of 5 samples			Pool of 6 samples
	E	N2	Result	E	N2	Result	E	N2	Result	E	N2	Result	E	N2
1 High	22.5	24.9	POS	23.3	25.6	POS	25.1	27.4	POS	25.1	27.5	POS	25.4	27.6
2 High	14.6	17.9	POS	13.4	16.2	POS	15.7	18.1	POS	16.1	18.4	POS	16.5	18.7
3 High	15.6	18.4	POS	14.9	17.4	POS	16.4	18.6	POS	17.1	19.4	POS	17.7	19.9
4 High	20.8	23.7	POS	17.7	20.2	POS	19.6	21.9	POS	20.2	22.7	POS	20.5	22.9
5 High	19.3	21.7	POS	18.1	20.5	POS	20.1	22.5	POS	20.7	23.3	POS	21.1	23.4
6 Int	26.2	28.8	POS	26.1	28.8	POS	28.0	30.4	POS	28.4	30.9	POS	28.5	31.2
7 Int	28.3	31.3	POS	31.6	34.4	POS	33.4	36.6	POS	34.6	37.1	POS	30.3	33.3
8 Int	29.6	32.5	POS	30.2	32.8	POS	32.0	35.0	POS	34.2	35.8	POS	30.2	32.9
9 Int	23.0	25.2	POS	21.6	23.7	POS	23.6	25.7	POS	24.3	26.4	POS	24.4	26.4
10 Int	31.2	34.0	POS	30.2	32.8	POS	32.2	35.4	POS	32.7	36.0	POS	32.7	35.8
11 Low	33.4	36.7	POS	31.1	33.8	POS	32.9	36.3	POS	32.4	35.1	POS	34.8	36.8
12 Low	33.2	36.4	POS	27.5	30.2	POS	33.4	36.6	POS	36.2	37.9	POS	35.6	39.3
13 Low	38.5	41.9	POS	33.7	36.9	POS	0.0	42.6	POS	0.0	41.2	POS	NA	41.0
14 Low	35.8	38.0	POS	38.5	38.3	POS	41.6	42.3	POS	37.8	43.2	POS	NA	42.2
15 Low	35.7	39.3	POS	35.8	39.4	POS	39.9	42.1	POS	40.5	41.4	POS	NA	41.9

The initial sample was pooled with negative samples to give the indicated pool sizes. The Ct values of the samples (based on the initial value obtained with the E target) were as follows: high, >25; int, 25–32; low, <33. NA = not available; the instrument does not provide Ct values for samples deemed negative, and the manufacturer's cutoff values are proprietary.