Factor XII Activity

Single-analyte tests

• Factor XII Activity 086322

  Plasma · Fasting not stated · Turnaround 2 - 3 days

  Method and collection

  Method

  The assay consists of the measurement of the clotting time, in the presence of cephalin and activator, in a system in which all the factors are present and in excess except factor XII, which is derived from the sample being tested. Testing coagulation factor activities requires that three dilutions be assayed and analyzed to produce a single result.9,10 The slope of the line created by plotting measured factor concentration against sample dilution is evaluated to discern the presence of inhibitors giving rise to nonparallelism.10 (Moreover, samples producing results on initial dilution falling outside the analytic measurement range of the assay are tested at additional dilutions to produce reportable results.10

  Preparation

  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. Do not draw from an arm with a heparin lock or heparinized catheter.

  Collection

  Blood should be collected in a blue-top tube containing 3.2% buffered sodium citrate.1 Evacuated collection tubes must be filled to completion to ensure a proper blood-to-anticoagulant ratio.2,3 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 unless the sample is collected using a winged (butterfly) collection system. With a winged blood collection set a discard tube should be drawn first to account for the dead space of the tubing and prevent under-filling of the evacuated tube.4,5 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 alternative 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. Please print and use the Volume Guide for Coagulation Testing to ensure proper draw volume.

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• Factor XII Activity With Inhibitor Reflex 086304

  Plasma · Fasting not stated · Turnaround 5 - 7 days

  Method and collection

  Method

  See individual activity test information for method information. The Bethesda titer measures the amount (titer) of an inhibitor antibody against a specific clotting factor.1 The test uses dilutions of the patient's plasma and determines the amount of antibody needed to neutralize 50% of the factor activity provided by pooled normal plasma with results expressed in Bethesda units (BUs). One Bethesda Unit (BU) is defined as the amount of an inhibitor that will neutralize 50% of one unit of the factor in normal plasma after 120 minutes incubation at 37°C. A higher titer indicates a stronger inhibitor, which can significantly impact treatment. A Bethesda titer assay is not performed when factor level exceeds 40% (i.e., in the absence of measurable factor activity inhibition).

  Preparation

  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. Do not draw from an arm with a heparin lock or heparinized catheter.

  Collection

  Blood should be collected in a blue-top tube containing 3.2% buffered sodium citrate.2 Evacuated collection tubes must be filled to completion to ensure a proper blood-to-anticoagulant ratio.3,4 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 unless the sample is collected using a winged (butterfly) collection system. With a winged blood collection set, a discard tube should be drawn first to account for the dead space of the tubing and prevent under-filling of the evacuated tubes.4,5 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 alternative 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. Please print and use the Volume Guide for Coagulation Testing to ensure proper draw volume.

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Panels that include this biomarker

• Contact Factor Evaluation Profile 117250

  4 analytes · Plasma · Fasting not stated · Turnaround 5 - 8 days

  Method and collection

  Method

  See individual tests.

  Collection

  Blood should be collected in a blue-top tube containing 3.2% buffered sodium citrate.21 Evacuated collection tubes must be filled to completion to ensure a proper blood to anticoagulant ratio.22,23 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, except when using a winged blood collection device (i.e., "butterfly"), in which case a discard tube should be used.24,25 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 .

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• Intrinsic Pathway Coagulation Factor Profile 500033

  4 analytes · Plasma · Fasting not stated · Turnaround 2 - 3 days

  Method and collection

  Method

  See individual tests.

  Preparation

  Do not draw from an arm with a heparin lock or heparinized catheter.

  Collection

  Citrated plasma samples should be collected by double centrifugation. Blood should be collected in a blue-top tube containing 3.2% buffered sodium citrate.1 Evacuated collection tubes must be filled to completion to ensure a proper blood to anticoagulant ratio.2,3 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, except when using a winged blood collection device (ie, "butterfly"), in which case a discard tube should be used.4,5 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 for 10 minutes and carefully remove 2/3 of the plasma using a plastic transfer pipette, being careful not to disturb the cells. Deliver to a plastic transport tube, cap, and recentrifuge for 10 minutes. Use a second plastic pipette to remove the plasma, staying clear of the platelets at the bottom of the tube. Transfer the plasma into a Labcorp PP transpak frozen purple tube with screw cap (Labcorp No. 49482). Freeze immediately and maintain frozen until tested. Please print and use the Volume Guide for Coagulation Testing to ensure proper draw volume.

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• Prolonged Activated Partial Thromboplastin Time (aPTT) 117796

  6 analytes · Plasma · Fasting not stated · Turnaround 2 - 3 days

  Method and collection

  Method

  See individual tests.

  Preparation

  Avoid warfarin (Coumadin®) therapy for two weeks and heparin therapy for two days prior to the test.

  Collection

  Citrated plasma samples should be collected by double centrifugation. Blood should be collected in a blue-top tube containing 3.2% buffered sodium citrate.1 Evacuated collection tubes must be filled to completion to ensure a proper blood to anticoagulant ratio.2,3 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, except when using a winged blood collection device (ie, "butterfly"), in which case a discard tube should be used.4,5 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 for 10 minutes and carefully remove 2/3 of the plasma using a plastic transfer pipette, being careful not to disturb the cells. Deliver to a plastic transport tube, cap, and recentrifuge for 10 minutes. Use a second plastic pipette to remove the plasma, staying clear of the platelets at the bottom of the tube. Transfer the plasma into a Labcorp PP transpak frozen purple tube with screw cap (Labcorp No. 49482). Freeze immediately and maintain frozen until tested. Please print and use the Volume Guide for Coagulation Testing to ensure proper draw volume.

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Single-analyte tests

• Factor XII Activity, Clotting 362

  Plasma · Fasting not stated · Turnaround Set up: Tues, Thurs, Sat

  Method and collection

  Method

  Photometric Clot Detection

  Collection

  Please submit a separate, frozen vial for each special coagulation assay ordered. Draw blood in a light blue-top tube containing 3.2% sodium citrate, mix gently by inverting 3-4 times. Centrifuge 15 minutes at 1500 g within one hour of collection. Using a plastic pipette, remove plasma, taking care to avoid the WBC/platelet buffy layer and place into a plastic vial. Centrifuge a second time and transfer platelet-poor plasma into a new plastic vial(s). Freeze immediately and transport on dry ice.

  Reference notes

  50-150 % normal

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