Table 2.

Comparison of standard curve to Ct measurements across all samples

A
	quantity
sample type	qty	18S-norm	fold-change
blood	63	62	41
urine	63	66	23

B
CT
CT	dCT	ddCT
81	63	24
74	54	18

Overall interlab CVs for qPCR analysis of 5 target genes in 10 cDNA samples. Gene expression was measured using a standard curve to calculate quantities (A) or by the ddCT method (B). The columns from left to right indicate the CV calculated for raw quantity (or CT), 18S-normalized quantity (dCT), and fold-change (ddCT) with one blood sample and one urine sample chosen as calibrator. The variability between sites was equivalent for blood and urine samples and for quantification strategy. In all cases, fold-change measurements were more similar between sites than sample-specific measurements.