Disagreement between bedside and laboratory activated partial thromboplastin time and international normalized ratio for various novel anticoagulants

During studies on warfarin, heparin and various anticoagulants with novel m echanisms of action, the activated partial thromboplastin time (aPTT) and t he (apparent) international normalized ratio (INR) from a bedside monitor ( Coagucheck Plus((R))) were compared with laboratory assay results. Data wer e compared using the Bland and Altman method of comparison where systematic differences result in significant slopes of the regression line. During he parin treatment, the bedside monitor largely underestimated the aPTT (slope =-0.80). During treatment with the direct thrombin inhibitor napsagatran (s lope=0.99), the pentasaccharides Org31540/SR90107A (slope=0.77) and SanOrg3 4006 (slope=0.35), and warfarin (slope=0.60), the bedside monitor underesti mated the aPTT at lower aPTT levels, while at higher aPTT levels it overest imated the laboratory values. The bedside monitor slightly overestimated th e INR during treatment with warfarin (slope=0.33). Apparent INR was largely overestimated during treatment with Org31540/SR90107A (slope=1.38), SanOrg 34006 (slope=0.97), Napsagatran (slope=1.23), and recombinant tissue factor pathway inhibitor (slope=1.48, P <0.001 for all regression lines). These r esults indicate that a substantial disagreement in aPTT or (apparent) INR e xists between the bedside monitor and laboratory assay during treatment wit h the studied 'classic' and novel anticoagulants. The amount of disagreemen t depended on the anticoagulant given. (C) 2001 Lippincott Williams & Wilki ns.