Table 2. Limit of detection of one KRAS exon 2 and one KRAS exon 4 mutations by ctKRAS mutation assay and detection of one BRAF codon 600 mutation and one NRAS exon 3 mutation by ctNRAS-BRAF mutation assay on samples mimicking plasma.
| Gene mutation | cfDNA concentration* | ctDNA concentration† | Mutated ctDNA concentration‡ | cfDNA total concentration§ | Ratio mutated copies / wild-type copies | Cq wild-type (control)|| | Cq mutated || | Mutation interpretation |
|---|---|---|---|---|---|---|---|---|
| ng/mL | ng/mL | ng/mL | ng/mL | % | ||||
| copies /mL | copies /mL | copies / mL | copies /mL | |||||
|
KRAS p.(Ala146Thr) |
460.0 | 9.00 x 10−2 | 4.50 x 10−2 | 460.09 | 1/10 000 | 27.7 | 39.2 | Detected |
| 138 000 | 28 | 14 | 138 028 | 0.010% | ||||
| 460.0 | 7.70 x 10−2 | 3.85 x 10−2 | 460.08 | 1/12 000 | 29.0 | 39.6 | Detected | |
| 138 000 | 23 | 11.5 | 138 23 | 0.009% | ||||
| 460.0 | 7.40 x 10−2 | 3.70 x 10−2 | 460.07 | 1/12 500 | 29.8 | - | Not detected | |
| 138 000 | 22 | 11 | 138 022 | 0.008% | ||||
|
KRAS p.(Gly12Val) |
460.0 | 4.00 x 10−2 | 4.00 x 10−2 | 460.04 | 1/11 500 | 28.1 | 38.3 | Detected |
| 138 000 | 12 | 12 | 138 012 | 0.009% | ||||
| 460.0 | 3.50 x 10−2 | 3.50 x 10−2 | 460.035 | 1/13 000 | 27.9 | 32.8 | Detected | |
| 138 000 | 10.5 | 10.5 | 138 010 | 0.008% | ||||
|
BRAF p.Val600Glu |
460.0 | 14.00 x 10−2 | 7.00 x 10−2 | 460.014 | 1/6 500 | 37.8 | 53.4 | Detected |
| 138 000 | 42 | 21 | 138 42 | 0.015% | ||||
| 460.0 | 10.50 x 10−2 | 5.25 x 10−2 | 460.0525 | 1/8 750 | 38.1 | 55.3 | Detected | |
| 138 000 | 32 | 16 | 138 032 | 0.011% | ||||
| 460.0 | 10.30 x 10−2 | 5.15 x 10−2 | 460.010 | 1/9 000 | 37.7 | - | Not detected | |
| 138 000 | 30 | 15 | 138 030 | 0.011% | ||||
|
NRAS p.Gln61Lys |
460.0 | 14.00 x 10−2 | 7.00 x 10−2 | 460.014 | 1/6 500 | 37.8 | 55 | Detected |
| 138 000 | 42 | 21 | 138 042 | 0.015% | ||||
| 460.0 | 13.00 x 10−2 | 6.50 x 10−2 | 460.013 | 1/7 000 | 37.7 | - | Not detected | |
| 138 000 | 40 | 20 | 138 040 | 0.014% | ||||
| 460.0 | 12.66 x 10−2 | 6.33 x 10−2 | 460.012 | 1/7 250 | 37.6 | - | Not detected | |
| 138 000 | 38 | 19 | 138 038 | 0.014% |
* cfDNA concentration: concentration of cfDNA in commercial plasma
† ctDNA concentration: concentration of ctDNA added in commercial plasma
‡ mutated ctDNA concentration = ctDNA concentration for homozygous mutation and ctDNA concentration/2 for heterozygous mutation
§ cf DNA total concentration = cfDNA concentration + ctDNA concentration. cfDNA total number of copies = cfDNA number of copies + ctDNA number of copies
|| cycle quantification.