Table 3.
Percentage of Patients in the Validation Cohort and in the Derivation-plus-Validation Cohort with an Ideal, Underestimated, or Overestimated Dose of Warfarin, as Estimated with the Pharmacogenetic Algorithm, Clinical Algorithm, and Fixed-Dose Approach in Patients Requiring Low, Intermediate, or High Actual Doses of Warfarin for a Therapeutic Effect.*
| Actual Dose Required | No. of Patients |
Ideal Dose | Underestimation | Overestimation | |||
|---|---|---|---|---|---|---|---|
| Percent | P Value† | Percent | P Value† | Percent | P Value† | ||
| Validation cohort only | |||||||
| ≤21 mg/wk | 324 | ||||||
| Pharmacogenetic approach | 33.0 | 0.008, <0.001 | 4.6 | 0.002, <0.001 | 62.3 | <0.001, <0.001 | |
| Clinical approach | 25.9 | <0.001 | 0.6 | 0.50 | 73.5 | <0.001 | |
| Fixed-dose approach | 0 | 0 | 100 | ||||
| >21 mg/wk to <49 mg/wk | 560 | ||||||
| Pharmacogenetic approach | 54.6 | 0.72, 0.31 | 26.8 | 0.14, <0.001 | 18.6 | 0.25, <0.001 | |
| Clinical approach | 53.6 | 0.55 | 29.8 | <0.001 | 16.6 | <0.001 | |
| Fixed-dose approach | 51.6 | 9.1 | 39.3 | ||||
| ≥49 mg/wk | 125 | ||||||
| Pharmacogenetic approach | 36.8 | <0.001, <0.001 | 63.2 | <0.001, <0.001 | 0 | 1.00, 1.00 | |
| Clinical approach | 9.6 | <0.001 | 89.6 | <0.001 | 0.8 | 1.00 | |
| Fixed-dose approach | 0 | 100 | 0 | ||||
| Derivation-plus-validation cohort | |||||||
| ≤21 mg/wk | 1711 | ||||||
| Pharmacogenetic approach | 35.0 | <0.001, <0.001 | 5.4 | <0.001, <0.001 | 59.7 | <0.001, <0.001 | |
| Clinical approach | 24.0 | <0.001 | 1.2 | <0.001 | 74.8 | <0.001 | |
| Fixed-dose approach | 0 | 0 | 100 | ||||
| >21 mg/wk to <49 mg/wk | 2716 | ||||||
| Pharmacogenetic approach | 55.9 | 0.02, 0.08 | 25.9 | <0.001, <0.001 | 18.2 | <0.001, <0.001 | |
| Clinical approach | 53.3 | 0.80 | 31.0 | <0.001 | 15.6 | <0.001 | |
| Fixed-dose approach | 53.7 | 8.9 | 37.4 | ||||
| ≥49 mg/wk | 625 | ||||||
| Pharmacogenetic approach | 32.8 | <0.001, <0.001 | 66.7 | <0.001, <0.001 | 0.5 | 1.00, 0.25 | |
| Clinical approach | 13.3 | <0.001 | 86.2 | <0.001 | 0.5 | 0.25 | |
| Fixed-dose approach | 0 | 100 | 0 | ||||
The ideal dose was defined as a predicted dose that was within 20% of the actual stable therapeutic dose of warfarin, underestimation was defined as a predicted dose that was at least 20% lower than the actual dose, and overestimation was defined as a predicted dose that was at least 20% higher than the actual dose.
For the pharmacogenetic approach, the first P value is for the comparison with the clinical approach, and the second for the comparison with the fixed-dose approach. The P value for the clinical approach is for the comparison with the fixed-dose approach.