Establishing the heparin therapeutic range using aPTT and anti-Xa measurements for monitoring unfractionated heparin therapy

Abstract

BackgroundUnfractionated heparin (UFH) has unstable pharmacokinetics and requires close monitoring. The activated partial thromboplastin time (aPTT) test has been used to monitor UFH therapy for decades in Korea, but its results can be affected by numerous variables. We established an aPTT heparin therapeutic range (HTR) corresponding to therapeutic anti-Xa levels for continuous intravenous UFH administration, and used appropriate monitoring to determine if an adequate dose of UFH was applied.MethodsA total of 134 ex vivo samples were obtained from 71 patients with a variety of thromboembolisms. All patients received intravenous UFH therapy and were enrolled from June to September 2015 at Gyeongsang National University Hospital. All laboratory protocols were in accordance with the Clinical and Laboratory Standards Institute guidelines and the College of American Pathologist requirements for aPTT HTR.ResultsAn aPTT range of 87.1 sec to 128.7 sec corresponded to anti-Xa levels of 0.3 IU/mL to 0.7 IU/mL for HTR under our laboratory conditions. Based on their anti-Xa levels, blood specimen distribution were as follows: less than 0.3 IU/mL, 65.7%; 0.3–0.7 IU/mL (therapeutic range), 33.6%; and more than 0.7 IU/mL, 0.7%. No evidence of recurring thromboembolism was observed.ConclusionUsing the conventional aPTT target range may lead to inappropriate dosing of UFH. Transitioning from the aPTT test to the anti-Xa assay is required to avoid the laborious validation of the aPTT HTR test, even though the anti-Xa assay is more expensive.

Update on the Clot Waveform Analysis

“…The APTT is a clotting time assay that is useful for diagnosing deficiencies in the coagulation factors of the intrinsic pathway, such as hemophilia, 6 the presence of inhibitors, such as lupus anticoagulant (LA), 7 and acquired hemophilia and for monitoring heparin treatment. 8 All coagulation tests were in the beginning performed by hand and so the timing was done using a stop watch; thus multiple assays and standardization of APTT were difficult to carry out with this manual method. The development of automatic optical coagulation analyzers has made it easy to perform multiple assays and enabled the standardization of the APTT reagents for LA and heparin.…”

An Evaluation of the Activated Partial Thromboplastin Time Waveform

“…The activated partial thromboplastin time (APTT) is an end-point clotting time assay that is useful for diagnosing deficiencies in the intrinsic pathway, such as hemophilia, 1 for diagnosing the presence of lupus anticoagulant (LA), 2 and for monitoring heparin treatment. 3 Automatic optical end-point coagulation analyzers have been recently developed, making it easy to perform multiple assays. Another benefit of optical end-point coagulation analyzers is the ability to visualize the clot reaction curve as the prothrombin time and the APTT.…”

Erroneous Activated Coagulation Time During Atrial Flutter Ablation

“…Conversely, in a patient on extracorporeal membrane oxygenation, the APTT may be prolonged into the therapeutic range due to factor deficiencies, and result in decreased heparin dosing that may lead to thrombosis [8]. e APTT is also affected by acute phase reactants and the lupus anticoagulant, and may be affected by liver disease [9]. In fact, it has been suggested that Anti-Xa assay supplant the APTT in patients on heparin therapy, as it may offer a smoother dose-response curve, with fewer blood draws, and fewer dosage adjustments [10].…”