Factor VIII Activity, Chromogenic

Antihemophilic Factor (AHF)

9 days

The FVIII chromogenic substrate assay measures the FVIII-dependent activation of FX using purified bovine coagulation factors.

49–126%

Causes for Rejection:
Ideally the patient should not be on anticoagulant therapy. Avoid warfarin (Coumadin®) therapy for two weeks prior to the test and heparin, direct Xa and thrombin inhibitor therapies for about three days prior to testing.

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This test is used in the measurement of factor VIII activity in hemophilia patients. The chromogenic assay can be used in place of the more commonly used one-stage assay (OSA) for a number of clinical indications where limitations of OSA require a secondary option for FVIII testing.

Plasma, Frozen

1 mL

Blue stopper 3.2% sodium citrate plasma evacuated tube

No special preparation is required for this test. You may eat, drink, and take your medications as normal, unless instructed otherwise by your healthcare provider.

Blood should be collected in a blue-top tube containing 3.2% buffered sodium citrate. Evacuated collection tubes must be filled to completion to ensure a proper blood to anticoagulant ratio. The sample should be mixed immediately by gentle inversion at least six times to ensure adequate mixing of the anticoagulant with the blood. A discard tube is not required prior to collection of coagulation samples. When noncitrate tubes are collected for other tests, collect sterile and nonadditive (red-top) tubes prior to citrate (blue-top) tubes. Any tube containing an alternate anticoagulant should be collected after the blue-top tube. Gel-barrier tubes and serum tubes with clot initiators should also be collected after the citrate tubes. Centrifuge and carefully remove the plasma using a plastic transfer pipette, being careful not to disturb the cells. Transfer the plasma into a Labcorp PP transpak frozen purple tube with screw cap (Labcorp No. 49482). Freeze immediately and maintain frozen until tested. To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested.