The protocol based on the heparin dose response curve is similar to that based on the reference range for aPTT, except that the decision points are basedon the aPTTs corresponding to known heparin concentrations, rather than based on a multiple of the mean.

If the target for aPTT monitoring is based on the heparin response curve, then the therapeutic range for aPTT corresponds to a heparin levels of 0.2-0.3 or 0.2-0.4 IU/mL


Example for a heparin response curve:


Heparin Dose


0.1 IU/mL

38.4 seconds

0.2 IU/mL

55 seconds

0.3 IU/mL

74.5 seconds

0.4 IU/mL

99 seconds


If the therapeutic target is based on a heparin level of 0.2 to 0.3 IU/mL, then the therapeutic range should be 55 to 74.5 seconds.

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