Hemostasis Reference Laboratory

APC Resistance Ratio (Activity) for Factor V Lieden

• Transaction Code: 3230-08
• CPT Code (Suggested): 85307

Plasma is diluted with Factor V deficient plasma and incubated with the APTT reagent for a standard period of time. Coagulation is initiated by the addition of CaC1₂ in the absence and the presence of Activated Protein C and the time for clot formation is recorded. Patients with an hereditary APC Resistance Ratio of < 2.0 are considered thrombophilic. Specific DNA test for Factor V mutation is also available. The functional (APC for Factor V) test is inaccurate in the presence of >1 IU/ml of unfractionated or low-molecular weight heparin and may be inaccurate in the presence of an abnormal APTT.

• Sample Required: 0.5 ml frozen plasma x4 or (2) 3.2% sodium citrated tubes, 5 ml each.
• See Sample Requirements when ordered with other tests.
• Normal Range: 2.0-5.0 ratio
• Analytic Time: Run weekly, depending upon requests