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Table 2 Comparison of sample quantification methods.

From: Routes to improving the reliability of low level DNA analysis using real-time PCR

Concentration/target copies μl-1 Number of negative reactionsNote 1 Measured concentration
   Ct of 55 included (as zero concentration)/target copies μl-1 Ct of 55 excluded/target copies μl-1
0.5 10 0.66 1.48
1.0 2 1.68 1.89
2.0 3 2.51 3.02
5.0 0 5.28 5.28
10.0 0 10.90 10.90
  1. Note 1: Number of reactions (of 18 replicates) failing to reach fluorescence threshold, and with Ct set to 55. Results showing the difference in sample concentration determined by either including or excluding amplification reactions with no measurable Ct value. The calibration curve was calculated from the low-retention data only, using the exclusion-by-sample method to remove samples with missing values, and the interpolated concentrations calculated using the low-retention plastic values only.