Monitoring Heparin in the Clinical Laboratory

Unfractionated heparin (UFH, commonly called heparin) is an indirect anticoagulant commonly administered prophylactically to inpatients at risk of thrombosis.  Anticoagulants, including UFH, are considered high alert medications when used for treatment. As such, assays monitoring levels of UFH are extremely important to avoid adverse effects for patients. This activity will provide improved understanding for clinicians and laboratorians related to the monitoring of UFH and related forms of heparin.  Emphasis will be placed on the role of the chromogenic anti-Xa assay as a measure of heparin activity along with clinical scenarios and outcomes studies.

• Describe the biochemical nature of heparin including low molecular weight heparin (LMWH) and ultra-low molecular weight synthetic forms such as fondaparinux.
• Review the anticoagulant mechanism of action of these various forms of heparin.
• Compare the activated PTT and the anti-Xa assay as a means of monitoring heparin.
• Explain the role of ATIII supplementation in the anti-Xa assay and its consequences.
• Discuss the clinical consequences of anti-Xa monitoring in the context of clinical scenarios.