ACTIVATED PROTEIN C RESISTANCE

Code
000.0000
Name
ACTIVATED PROTEIN C RESISTANCE
Category
None
Department
Send-Out
Start Date
Expiration Date
Synonyms
APCR; APC-R; APC Resistance
CPT Codes
85307
Site
SBMF
Reference Test
25185
ATLAS Test Code

Specimen Information

Type

Light blue top (3.2% buffered sodium citrate) tube--Platelet poor plasma (PPP)

Volume

2.0 mL (Two pour-off tubes, 1.0 mL each)

Transport Info

Separate plasma from cells immediately
• Promptly centrifuge 15 minutes
• Carefully transfer plasma portion of sample to separate plastic tube using plastic pipette
• Centrifuge transferred plasma sample again to produce platelet-poor plasma (PPP)
• Use second plastic pipette to carefully transfer PPP sample into plastic aliquot tubes
Frozen

Fasting Required?
False
Patient Instructions

Collect prior to initiation of anticoagulant therapy

Individuals to be investigated should not be on heparin or vitamin K antagonist therapy. In the latter case, treatment should be discontinued for approximately one week until the baseline prothrombin time has been reestablished.

Reference Range

Ratio > 1.5 is a normal response.

Ratio <= 1.5 is most commonly, but not exclusively consistent with factor V Leiden mutation. Suggest submitting a new sample for factor V Leiden genotype assay for confirmation.

Ratios between 1.5 and 2.1 may suggest low levels of protein C and should be investigated further.

Methodology

Clot Detection

Clinical Significance

Used to screen for the factor V gene mutation.

A hereditary disorder in the Protein C anticoagulant pathway has been described which constitutes an important risk factor for thromboembolic disease. This disorder, denoted APC resistance, is characterized by an abnormally low anticoagulant response in human plasma on addition of human APC. 85-90% of cases with APC resistance are explained by a mutation in the Factor V gene, which renders one of the cleavage sites in factor Va less susceptible to cleavage due to an amino acid substitution (Arg/Gln). In patients with venous thromboembolic disease the incidence of resistance has been found to be 20-40%. APC Resistance provides an APTT-based assay to semi-quantitative determination of the response towards human APC. The prolongation of the basal APTT clotting time after addition of APC is shorter in plasma from individuals with APC resistance than from individuals with normal response to APC.

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