I wants to know the range calculation, based on the recommended method for establishing the PTT range for heparin therapy.
Yes, you can see calculate by online calculator: 1. Online calculator http://www.globalrph.com/heparin.htm
Also, I am suggesting you some of the articles and guidelines for Heparin Management take a look:
Thank you Mr. Hafeez, but my question is not regarding the dose of heparin in different types of patients, actually there is unexpected wide variance between therapeutic anticoagulation ranges for aPTT testing. It is because of the variation between lots of reagents yet the differences in reagent sensitivity, heparin manufacturing and type of heparin. So I just wants to know how can I calculate heparin therapeutic range for different PTT reagents with different types of lots.
Above articles and guidelines are helping to monitor heparin therapy with lab based monitoring of aPTT. Because the fact of wide variance of aPTT is not only the cause but also heparin itself. Heparin are based on its pharmacokinetic, biophysical, and nonanticoagulant biological properties. All are caused by the AT-independent, charge-dependent binding properties of heparin to proteins and surfaces. The biophysical limitations occur because the heparin-AT complex is unable to inactivate factor Xa in the prothrombinase complex and thrombin bound to fibrin or to subendothelial surfaces. Platelets, fibrin, vascular surfaces, and plasma proteins modify the anticoagulant effect of heparin. Platelets limit the anticoagulant effect of heparin by protecting surface factor Xa from inhibition by the heparin-AT complex and by secreting PF4, a heparin-neutralizing protein. Since an elevated PTT correlates poorly with heparin-induced bleeding, the primary risk of an inaccurate therapeutic PTT range would be thrombosis secondary to inadequate anticoagulation (ie, underestimate the elevation of the PTT necessary to achieve therapeutic anticoagulation).
According to CAP, It has been known for many years that the response of the aPTT to heparin varies widely secondary to the variability in reagents, instruments, patient response to heparin and, to a small degree, the heparin itself.
Many laboratories may find themselves in the position of attempting to validate their PTT therapeutic ranges but being unable to comply with current accreditation recommendations.
You can also see CAP Coagulation Resource Committee guideline for Validation of heparin sensitivity of the aPTT using an assay of heparin.
http://www.captodayonline.com/Archives/feature_stories/1004Heparin.html
Recently, another method of determining the Heparin Therapeutic Range was developed utilizing a procedure derived from Brill-Edwards, et al, in which aPTT values and heparin levels are obtained from patients actually receiving heparin. Using linear-regression, a graph is prepared that correlates the aPTT in seconds to the heparin Anti-Xa units. The ranges established, are the time in seconds equivalent to 0.1 to 0.3 and 0.3 to 0.7 Anti-Xa units of heparin.
Therapeutic Range =
0.1 Units = 47 seconds (aPTT)
0.3 =64 seconds
0.7 =98 seconds
https://www.utmb.edu/LSG/Pages/Heparin_Therapy.aspx
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