This figure demonstrates absolute cDNA copy numbers from naïve (n = 5) vs. trauma (n = 5) samples for PPIA (high-copy, non-regulated gene), iNOS and IL-1β (both low-copy, regulated genes). An equal amount of each sample was reverse-transcribed, using all four kits. A significantly higher cDNA expression was present in trauma vs. naïve samples for PPIA (kit 2, p = 0.002; kit 3, p = 0.014; and kit 4, p = 0.027), iNOS and IL-1β (all kits, p<0.05). Absolute and relative results vary significantly between the kits used (a-c). In accordance with our previous findings, the mRNA/cDNA ratio varies substantially between the kits (d) (although identical starting material was used) and between genes (although reverse-transcribed by the same kit under equal experimental conditions). All bar charts show mean ± S.D.