APC RESISTANCE UNIVERSITY
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APC RESISTANCE PHENOTYPING
Coatest® APC™ Resistance is the classic APTT-based assay for the detection of the APC resistance phenotype, i.e. the poor anticoagulant response to activated protein C (APC). The test result (APC ratio) gives an estimation of the anticoagulant function in vivo and provides information on the thrombotic risk associated with inherited and possibly acquired APC resistance.
Assay procedure
Citrated and centrifuged plasma is incubated with the APTT reagent for a standard period of time. Coagulation is triggered by the addition of CaCl2 in the absence and presence of exogenous APC and the time for clot formation is recorded. The relationship between the two clotting times is expressed as an APC ratio.
Calibration
The actual APC ratio corresponding to a borderline response to APC may vary slightly depending on the type of instrumentation used as well as on the instrument condition. It is recommended that users establish their own cutoff value for their instrument as described in the kit insert.
Results
APC resistance is indicated when the APC ratio is below the cut-off value.
Kit Contents
1. CaCl2, 1 x 8 mL 0.025 mol/L in Tris buffer containing 0.5% bovine serum albumin.
2. APTT reagent, 1 x 16 mL Purified phospholipid with colloidal silica as contact activator.
3. APC/CaCl2, 4 x 2 mL Human APC colyophilized with CaCl2
Stability in solution (2–8 °C)
1. CaCl2, 1 month
2. APTT reagent, 1 month
3. APC/CaCl2, 5 days
Repeatability and precision
The reproducibility of the clotting times was determined in the presence and absence of APC by analysis of three plasma samples with varying responses to APC. The analyses were performed on 7 different occasions, including 5 replicates of each plasma. Instrument: ACL.
HRP = High response plasma
CPL1 = Control Plasma Level 1 (normal response)
CPL2 = Control Plasma Level 2 (low response)
| CaCl2 | Within series | Between series | |
|---|---|---|---|
| HRP | 29.9 s | CV=1.8% | CV=4.2% |
| CPL1 | 32.0 s | CV=2.0% | CV=3.9% |
| CPL2 | 32.2 s | CV=1.1% | CV=0.8% |
| APC/CaCl2 | Within series | Between series | |
|---|---|---|---|
| HRP | 122 s | CV=2.4% | CV=2.0% |
| CPL1 | 116 s | CV=4.3% | CV=5.0% |
| CPL2 | 64.5 s | CV=1.4% | CV=1.6% |
| APC ratio | Between series | ||
|---|---|---|---|
| HRP | 4.1 | CV=5.0% | |
| CPL1 | 3.6 | CV=3.3% | |
| CPL2 | 2.0 | CV=1.4% |
Test limitations
Abnormal APTT, vitamin K antagonist therapy, heparin therapy.
Number of determinations per kit
80–160
Catalog #
K822643
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