Harris, L. F. and Killard, A.
Heparin monitoring: From blood tube to microfluidic device.
In: Piyathilake, D. E. and Liang, R., eds.
Heparin, properties, uses and side effects.
New York: Nova Science Publishers.
Publisher's URL: https://www.novapublishers.com/catalog/
Heparin anticoagulant therapy has been pivotal in both the treatment and prophylaxis of thrombotic disease for many decades. It remains standard practice to monitor unfractionated heparin (UFH) therapy due to its unpredictable pharmacokinetics. The advent of low molecular weight heparins (LMWHs) reduced the need for continuous laboratory monitoring due to the improved dose-response relationships and pharmacokinetics of these drugs. However, special patient cohorts exist where monitoring becomes essential irrespective of the drug being administered.
The standard assays used for heparin (UFH and LMWH) monitoring include the activated partial thromboplastin time (aPTT), activated clotting time (ACT), thrombin time (TT), and the anti-Xa assay. Clot-based assays such as the aPTT, ACT, and TT, comprise some of the more traditional assays that are employed in the haemostasis laboratory. The anti-Xa assay is a chromogenic assay more commonly used for monitoring patients on LMWH therapy.
Over the last few years, significant efforts have been made towards point-of-care testing (POCT) which offers greater ease of use, convenience, efficiency, and faster turnaround times than laboratory-based tests. POCT, as its name suggests describes testing that can be performed near or beside the patient, be it in a primary care facility such as a doctor’s surgery, the operating theatre, the emergency room or even in the home.
While many POC coagulation assays are available on the market, there is a certain degree of reticence among the medical community in their uptake, as these technologies compete with conventional laboratory testing, accompanied by reports of poor correlations between the two systems. The popularity of these devices remains controversial as they can face major challenges in the areas of regulatory compliance, quality control, and financial cost.
Many POC technologies are commercially available for coagulation tests. For heparin monitoring in particular, the devices available, e.g., Hemochron and i-STAT, can perform tests such as aPTT, ACT, and TT. While current POC devices for measuring heparin are suitable for use in the hospital setting rather than in the home, the POC technologies of the future will need to encompass all patient settings. The future of coagulation testing could see a move away from the more traditional clot-based tests towards more modern analytical technologies, with a knock-on effect of improved assay variability, precision, and reliability. Such developments can only improve medical outcomes associated with heparin testing.
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