Table 1. FFPE sample characteristics in the diagnostic (A) and in the unfavorable control group (B).
| group A | group B | ||
| block age (210 cases) | |||
| all samples | 135 | 75 | |
| 2005–2008 | 114 | 29 | |
| before 2005 | 21 | 46 | |
| percentage of tumor cells | |||
| >30% | 105& | 75& | |
| >10–30% | 24 | none | |
| ∼10% | 6 | none | |
| DNA quantity (ug/ml) | |||
| mean | 81,7 | 67,4 | |
| range (min–max) | 12,3 to 383,5 | 12,5 to 147,3 | |
| A260/280 ratio | |||
| mean | 1,67 | 1,27 | |
| range (min–max) | 1,21 to 1,98 | 1,18 to 2,6 | |
| 1,6–1,8 (n samples) | 94/135 | 2/75 | |
| DNA fragmentation test (n samples) | |||
| ≥300 bp (less fragmented) | 102 (75,6%) | none | |
| 100 & 200 bp (intermediate) | 17 (12,6%) | 2 | |
| 100 bp or no product (heavily fragmented) | 16 (11,8%) | 73 | |
| DNA control curve Ct | |||
| KRAS-TMGB (∼50 ng/reaction) | |||
| n samples tested | 135 | 75 | |
| mean* | 28,46 | 34,06 | p<0.0001 |
| ±SD* | 2,71 | 2,07 | |
| range (min–max) | 23,73 to 36,61 | 30,58 to 39,37 | |
| Ct ≤29** (n samples) | 52 (38,5%) | 0 | |
| Ct ≤33# (n samples) | 128 (94,8%) | 26 (34,6%) | |
| DxS-KRAS (∼50 ng/reaction) | |||
| n samples tested | 29 | 66 | |
| meanˆ | 31,61 | 36,60 | p<0.0001 |
| ±SDˆ | 3,49 | 2,78 | |
| range (min–max) | 26,21 to 39,49 | 31,6016 to 40 | |
| Ct ≤29** (n samples) | 8 (27,5%) | 0 |
& = >50% tumor cells for 88 samples in group A and all samples in group B
* = values from all samples (n = 210 for this test) for the DNA control assays employed (7 assays)
** = Ct (Cycle threshold) limiting value for reliable highest sensitivity assessments with each test (<0.7% mutant tumor cells with the KRAS-TMGB and <1% with the DxS-KRAS test, respectively)
# = Ct value for reliable assessments with a sensitivity of ∼7% tumor cells
ˆ = values from all samples tested (n = 95 for this test) for the DNA control assay employed (1 assay)