Activated Protein C Resistance (APCR)

Coagulation

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Description

Activated protein C resistance is defined as a plasma's poor anticoagulant response to added activated protein C ( APC ).

When coagulation is activated in the blood stream, protein C (PC) is converted to the anticoagulant activated protein C (APC) which destroys activated factor V (FVa) and activated factor VIII (FVIIIa), reducing risk of venous thromboembolism. A normal APCV test effectively rules out the presence of factor V Leiden in plasma.

Around 3-5% of the UK population shares a mutation in FV that reduces the anticoagulant effect of APC; this is factor V Leiden (FVL). FVL lacks a site required for destruction of factor FVa and the FVa persists in the blood longer than normal, increasing the tendency to venous thrombosis by around 5-fold if heterozygous, and more so in the presence of other risk factors. Subjects homozygous for FVL are at much greater risk. Rare patients with FVL have an allelic gene that does not function and the APCV test result suggests homozygous FVL and the patient has similar thrombotic risk as homozygous subjects.

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Sample Type

Plasma and blood cells ( Citrate Blue ) x 1

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Reference Range

Reference range indicated on report.

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Turnaround Time

Within 2 weeks

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Testing Frequency

Weekly

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External Notes

An abnormal APCR indicates that factor V Leiden is almost certainly present and genetic confirmation of factor V Leiden is carried out on the specimen.

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

We are unable to test when patient is Heparin or on Direct Oral Anticoagulants (DOAC) including Rivaroxaban, Apixaban, Endoxaban and Dabigatran and we carry out the genetic test for factor V Leiden instead of the APCV test which is a screen for FV Leiden.

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References

Moore et al, Recommendations for clinical laboratory testing of activated protein C resistance; communication from the SSC of the ISTH J Thromb Haemost. 2019.

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See Also

Factor V Leiden

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