Table 1

Determination of intra- and inter-assay variations

Probe set	Samples (n = 3)	Replicates			Mean	SD	p value*
Probe set	Samples (n = 3)	Median relative copy number			Mean	SD	p value*
*Two sample t test comparing replicate samples to normal set (n = 474).
(A) Intra-assay variation
Chromosome 13	47, XY, +13	1.34	1.31	1.41	1.35	0.051	<0.01
Chromosome 13	46, XX	1.00	1.06	1.07	1.04	0.037	0.20
Chromosome 18	47, XY, +18	1.33	1.34	1.42	1.36	0.049	<0.01
Chromosome 18	46, XX	1.05	1.03	1.08	1.05	0.025	0.14
Chromosome 21	47, XY, +21	1.42	1.39	1.54	1.45	0.079	<0.01
Chromosome 21	46, XX	1.11	0.99	0.99	1.03	0.069	0.26
(B) Inter-assay variation
Chromosome 13	47, XY, +13	1.46	1.35	1.32	1.38	0.073	<0.01
Chromosome 18	47, XY, +18	1.50	1.40	1.40	1.43	0.057	<0.01
Chromosome 18	47, XY, +18	1.36	1.32	1.44	1.37	0.061	<0.01
Chromosome 21	47, XY, +21	1.44	1.47	1.37	1.43	0.051	<0.01
	47, XY, +21	1.43	1.46	1.36	1.42	0.051	<0.01
	47, XY, +21	1.49	1.33	1.38	1.40	0.081	<0.01