Clinical Use of the Heparin Nomogram-Reply

In Reply. — We agree with Raschke and Hertel that there is marked variability in the responsiveness of various commercial activated partial thromboplastin time (APTT) reagents to heparin and that our nomogram may not be generalizable to other APTT reagents. The advantage of our nomogram is that it standardized the monitoring of heparin in our institution and led to the rapid achievement and maintenance of therapeutic APTT values. To use our nomogram with a thromboplastin of different sensitivity, it would be necessary to first compare patient plasma samples using our thromboplastin (Actin FS, Dade, Mississauga, Ontario) and the new thromboplastin and then convert the APTT observed with the new thromboplastin to that with Actin FS. For example, in the example Raschke provides, an APTT of 35 seconds with Dade Actin thromboplastin corresponds to 60 seconds using Actin FS. This is the lower limit of the therapeutic range for our nomogram