Figure 5.Clotting curve shapes determine the clotting times (prothrombin times here), but not vice versa. The slopes and amplitudes of the clotting curves differ significantly and imply variable coagulation potential. However, the clotting times (prothrombin times here) are the same for all six test samples.|@|~(^,^)~|@|The clotting curve can be differentiated by a numerical method, and the 1^st and 2^nd derivative curves can be drawn. If the light transmission is read (turbidimetry) for clot detection, the 1^st and the 2^nd derivative peaks are directed downward (A). Conversely, if scattered light is read (nephelometry), the 1^st and the 2^nd derivative peaks are directed upward (B).|@|~(^,^)~|@|The clotting time and the CWA parameters present different aspects of a clotting reaction. The clotting curve parameters were collected from randomly selected blood samples referred for PT and APTT. The CWA parameters (|min1| and |min2|) and the clotting times (PT and APTT) were obtained from each plasma sample and dot-plotted on |min1| vs. PT (A), |min2| vs. PT (B), |min1| vs. APTT (C), and |min2| vs. APTT (D) planes. It is apparent by a simple visual ex-amination that both PT and APTT are poorly correlated with |min1| or |min2|. Samples with the same PT or APTT demonstrated a wide range of |min1| or |min2| values.|@|~(^,^)~|@|PT and APTT are technically defined as the time needed for the clotting velocity and acceleration to reach the maximum after adding each reagent to plasma. Thus, PT is the time point of the min1 and APTT of the min2.|@|~(^,^)~|@|VWF:RCO can be automated by replacing platelets of the original VWF:RCO with microparticles. In the method developed by Werfen, ristocetin primed plasma VWF binds glycocalicin. The bound glycocalicin molecules can be detected by anti-glycocalicin-coated microparticles (A). Alternatively, the glycocalicin with a GOF mutation of platelet type VWD can be used without ristocetin, as for the reagent from Siemens (B).

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