Heparin Ratio

Coagulation

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Description

Heparin is one of the most commonly prescribed anti-coagulant drugs for people at risk of thrombosis. Heparin works by enhancing the natural anticoagulant activity of Antithrombin. Unfractionated Heparin (UFH) is the standard clinical preparation and can be given SC or IV. It has a high affinity for other proteins in the blood and as a result bioavailability is only around 30%. This means that the pharmacokinetics are not easily predicted within any one patient and heparin therapy should be regularly monitored.    

The most commonly used method for control of heparin therapy is the activated partial thromboplastin time (APTT). The result is reported as a ratio (HR) according to the standardised reporting protocols recommended.

This is only appropriate for monitoring continuous intravenous unfractionated heparin (UFH) therapy.

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Indications

The APTT is prolonged in patients receiving unfractionated Heparin. The Heparin Ratio can therefore be used to monitor therapy.

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Sample Type

Plasma (Citrate 2.7ml Blue top) x 1

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Reference Range

For Heparin Ratio please refer to Trust protocol for therapeutic range.

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Turnaround Time

Within 1 hour

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Testing Frequency

Daily/continuous processing 24 hours.

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External Notes

The accuracy of all coagulation tests is greatly influenced by pre analytical variables. It is essential that sample quality is given the highest of priorities. Samples which fail to meet quality criteria including age of sample, specimen fill (>90%), haemolysed, clotted or activated samples will be rejected and a repeat sample requested.

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Patient Preparation

No specific requirements.

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References

Guidelines on the Laboratory aspects of assays used in haemostasis and thrombosis Mackie I, Cooper P, Lawrie A, Kitchen S, Gray E, Laffan M.

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Please note: the above information is subject to change and we endeavour to keep this website up to date wherever necessary.