Table 3.
Inter-day and Intra-day variation for estimation of plasma levels of warfarin and 7-hydroxy warfarin (n = 6).
| Nominal concentration in plasma (μg/ml) | Concentration found in plasma (μg/ml) (mean ± SD) | R.S.D. (%) | Bias (%) |
|---|---|---|---|
| Inter-day | |||
| Warfarin 2.5 | 2.32 ± 0.13 | 6.25% | −7.2 |
| 7-hydroxy warfarin 2.5 | 2.45 ± 0.28 | 3.26% | −2.0 |
| Warfarin 5 | 4.79 ± 0.28 | 5.89% | −4.2 |
| 7-hydroxy warfarin 5 | 4.65 ± 0.14 | 3.14% | −7.0 |
| Intra-day | |||
| Warfarin 2.5 | 2.39 ± 0.13 | 5.52% | −5.2 |
| 7-hydroxy warfarin 2.5 | 2.41 ± 0.10 | 3.61% | −3.6 |
| Warfarin 5 | 4.73 ± 0.39 | 8.36% | −5.4 |
| 7-hydroxy warfarin 5 | 4.74 ± 0.11 | 2.39% | −5.2 |
RSD – Relative standard deviation, Bias was calculated as (concentration found in plasma − expected concentration/expected concentration × 100).