Fig. 2. 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).

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