aPTT

Single-analyte tests

• aPTT Mixing Studies 117330

  Plasma · Fasting not stated

  Method and collection

  Method

  When a mixing study is ordered, an initial aPTT test is performed to determine the extent of testing to be performed. If the initial aPTT result is within the normal range, no further testing is warranted.1 Also, a mixing study is only clinically informative when the aPTT result is significantly increased relative to the Upper Reference Limit (URL) (Labcorp defines significant elevation of the aPTT to be more than three seconds above the URL). This reflects the fact that both minimal factor deficiencies and weak inhibitors can be overcome by addition of NPP resulting in correction on Immediate Mix. Since a mixing study is of no value in distinguishing these distinct causes of the minimally extended aPTT, no further testing beyond the initial aPTT is warranted in these cases. For the Immediate Mix, the patient specimen is mixed 1:1 with normal platelet-free plasma and an aPTT is performed on this mixture If the Immediate Mix fails to correct into the reference interval of the aPTT, no further testing is performed. If the Immediate Mix corrects into the normal range, an Incubated Mix and Incubated Mix Control tests are performed to identify time and/or temperature dependent inhibitors. For the Incubated Mix, an aliquot of the normal plasma/patient plasma mixture is incubated at 37°C for one hour and then an aPTT is performed For the Incubated Mix Control, normal plasma and patient plasma are also incubated separately and then mixed after incubation as a control for possible factor degradation during incubation; an aPTT is performed on this mixture

  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

  Citrated plasma samples should be collected by double centrifugation. Blood should be collected in a blue-top tube containing 3.2% buffered sodium citrate.11 Evacuated collection tubes must be filled to completion to ensure a proper blood to anticoagulant ratio.12,13 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.14,15 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. Deliver to a 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.

  Reference notes

  Activated Partial Thromboplastin Time (aPTT)16-18 Age | Range 1d | 29–38 sec 3d | 25–36 sec 1 to 11 m | 30–39 sec 1 to 5 y | 29–37 sec 6 to 10 y | 27–37 sec 11 to 16 y | 25–34 sec >16 y | 23–34 sec

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• Partial Thromboplastin Time (PTT), Activated 005207

  Plasma · Fasting not stated · Turnaround Within 1 day

  Method and collection

  Method

  The aPTT reagent consisting of silica mixed with synthetic phospholipid is mixed with the patient plasma. The silica provides a negatively-charged particulate surface for the activation of the contact pathway of coagulation. Calcium chloride is then added to the sample/reagent mixture to initiate clot formation. The time to clot formation is measured photo-optically.

  Preparation

  Draw specimen one hour before next dose of heparin if heparin is being given by intermittent injection. 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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Panels that include this biomarker

• Prothrombin Time (PT) and Partial Thromboplastin Time (PTT) 020321

  3 analytes · Plasma · Fasting not stated · Turnaround Within 1 day

  Method and collection

  Preparation

  Draw specimen one hour before next dose of heparin if heparin is being given by intermittent injection. 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.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. To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested. Please print and use the Volume Guide for Coagulation Testing to ensure proper draw volume.

  Reference notes

  See table. Age | Range6-8 Activated Partial Thromboplastin Time (aPTT) 1 d | 29–38 sec 3 d | 25−36 sec 1 to 11 m | 30−39 sec 1 to 5 y | 29−37 sec 6 to 10 y | 27–37 sec 11 to 16 y | 25–34 sec >16y | 23–34 sec Prothrombin Time (PT) 1 d | 14.4−16.4 sec 3 d | 13.5−16.4 sec 1 to 11 m | 11.5−15.3 sec 1 to 5 y | 12.1–14.5 sec 6 to 10 y | 11.7−15.1 sec 11 to 16 y | 12.7–16.1 sec >16y | 12.2–14.9 sec International Normalized Ratio (INR) 0 to 1 m | 0.9−1.4 >1 m | 0.9−1.2

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• Abnormal Bleeding Profile 116004

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

  Method and collection

  Method

  See individual tests.

  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.

  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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• Factor VIII Inhibitor Profile, Comprehensive 117157

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

  Method and collection

  Method

  The factor VIII inhibitor (Bethesda titer) assay is performed using an activated partial thromboplastin time (aPTT)-based test system.6 Serial dilutions are made of patient plasma with veronal buffered saline, then mixed with normal plasma containing close to 100% factor VIII activity and are then incubated for one hour. An aPTT-based factor VIII assay using factor VIII-depleted plasma substrate is then performed on these incubated mixtures. Results are compared to those of incubated normal plasma. One Bethesda unit is defined as the amount of factor VIII inhibitor that neutralized 0.5 IU of factor VIII in this system. The number of serial dilutions tested is based on the anticipated level of the inhibitor.

  Preparation

  The patient should not be anticoagulated. 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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• Menorrhagia Profile 336572

  5 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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• Disseminated Intravascular Coagulation (DIC) Profile 116012

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

  Method and collection

  Method

  See individual tests.

  Preparation

  None

  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.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 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. Please print and use the Volume Guide for Coagulation Testing to ensure proper draw volume.

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Single-analyte tests

• Partial Thromboplastin Time, Activated 763

  One full unopened 3.2% sodium citrate (light blue-top) tube · Fasting not stated · Turnaround Set up: Daily (Day shift and Night shift); Report available: 2 days

  Method and collection

  Method

  Photo-Optical Clot Detection

  Collection

  Unopened light blue-top tube: Correct ratio of blood to citrate is critical. Do not overfill or underfill collection tube. Mix by inversion 4 times. For non-heparinized patients, maintain specimen at room temperature. Do not uncap. Stable 24 hours at room temperature. Platelet-poor plasma: Centrifuge light blue-top tube 15 minutes at approximately 1500 g within 60 minutes 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. Plasma must be free of platelets (<10,000/mcl). Freeze immediately and ship on dry ice. Whole blood: The tubes should be at 100% +/- 10% fill volume in order to obtain the correct ratio.

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