Diagnostic Use
The APCR test screens for hereditary or acquired resistance to activated protein C, which is a natural anticoagulant. It is used in the evaluation of thrombophilia, especially in patients with VTE – unexplained, recurrent, or with a positive family history.
Interpretation
Tests performed from the 4th of February 2014 will be performed with a new method that bases the result on a clotting time. A time of < 120 has a >95% correlation with the presence of Factor V Leiden mutation. Clotting times between 120 and 130 seconds should be considered equivocal, repeat testing or molecular studies are suggested.
An APCR clotting time <120 seconds should be confirmed by molecular studies for Factor V Leiden(if not tested previously). This requires a 10 mL CPD (yellow top) tube. Molecular studies will identify homozygous or heterozygous state.
Factor V Leiden has a prevalence of 5 – 10 % in the European population and 20 – 50% of patients with venous thromboembolism.
Reference Intervals
> 2.0 prior to the 4th of February 2014
≥ 120 seconds after the 4th of February 2014
Limitations / Interference
This test can be performed during heparin therapy (up to 1 IU/mL) or once stabilised on warfarin.
The presence of aprotinin in the plasma may lead to a false positive result.
Please indicate on the form if patient is receiving Direct Anticoagulant therapy.
Uncertainty of Measurement
10%