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Table 2 Parameters of the ILPCR assay for CEA in human serum a)

From: Immunoliposome-PCR: a generic ultrasensitive quantitative antigen detection system



CV of repeatability b)

3 % (10-10 M) to 6 % (10-16 M)

CV of reproducibility b)

0.7 % (10-10 M) to 1.8 % (10-16 M)

Linear correlation coefficient (r) c)


Dynamic range


Detection threshold (Ct) d)


Limit of Detection (LOD) e)

10-16 M (13 fg/ml), ~6,000 molecules

Precision at LODf)

~500 molecules

Minimum Detectable Concentration (MDC) g)

10-17 M (1.3 fg/ml), ~600 molecules

Sensitivity h)

100 % (10-15 M), 87 % (10-16 M)

Specificity i)

100 %

  1. a) All parameters were determined using measurements from a total of 11 assays (n = 11).
  2. b) Coefficient of variance (CV) values increase with decreasing CEA concentration likely due, in part, to the stochastic effects associated with measuring very low analyte concentrations in small sample volumes.
  3. c) The indicated value is the linear correlation coefficient resulting from the fit of the data from 10-10 to 10-16 M CEA of the dose–response curve shown in Figure 4.
  4. d) The detection threshold is a measure of the noise level of the assay and is defined as the average Ct of the blank (all assay components except the antigen) minus 3 times the standard deviation of the blank.
  5. e) The LOD is defined as the lowest concentration within the linear region of the dose–response curve that yields a Ct value ≤ the detection threshold. The LOD corresponds to a Ct value of 29.32, which is well below the detection threshold of the assay (Ct = 30.97).
  6. f) A measure of the assay precision at the LOD was estimated by determining the number of molecules in the 100-μL sample at the LOD (6,023) and the associated upper and lower 95 % confidence limits, which yielded values of 6,530 and 5,550 molecules, respectively.
  7. g) The MDC is the lowest CEA concentration that is ≤ the detection threshold as determined from the second linear region of the dose–response curve of Figure 4 (the green dashed line from 10-16 to 10-18 M CEA).
  8. h) The assay sensitivity (percentage of the assays yielding an LOD ≤ the indicated CEA concentration) based upon the eleven ILPCR assays performed.
  9. i) The assay specificity was determined using multiple samples derived from a single CEA-negative human serum reference specimen; therefore, the specificity must be taken as preliminary.