Statistical correlations between the TAS methods and the reference
PT, aPTT, and ACT are listed in Table 2. Given the frank differences
between Innovin and the TAS ISI values, the PTs were not
expected to match and did not (R2 = 0.63, data not shown). Only
the INRs were correlated (R2 = 0.953) for all samples. This correlation
did not change significantly when samples from patients on
oral anticoagulant therapy of ≥7 days were analyzed separately (R2 =
0.949). The regression analysis and bias plot graphs (Fig. 1) indicate
fairly even distribution, but there appears to be a negative bias
between the TAS and laboratory methods at INRs of greater than
4.5. Increasing bias for PTs and INRs outside the therapeutic interval
has been noted in other studies [7,8]. The TAS prothrombin