4 - 8 days
Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.
For more information, please view the literature below.
Blue-top (sodium citrate) tube
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. 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.
Freeze. Stable at room temperature for four hours.
Do not draw from an arm with a heparin lock or heparinized catheter.
Measurement of prekallikrein factor concentration
Factor prekallikrein activity is determined utilizing an aPTT-based one-stage clotting time assay. Factor prekallikrein-depleted plasma is used as the substrate, and the clotting time with the patient plasma is compared to the clotting time of normal pooled plasma.
Prekallikrein is a single-chain serine protease synthesized in the liver that circulates in two forms having molecular weights of 85 and 88 kilodaltons.6 Prekallikrein's plasma concentration is 35 to 45 mg/mL. It circulates in an equimolar complex with high molecular weight kininogen (HMWK), and has a plasma half-life of 24 hours. Kallikrein liberates kinins from kininogens, activates factor XII and plasminogen, converts protein to renin, destroys C1 components, and interacts with leukocytes.
Factors VIII, IX, XI, XII, prekallikrein, and high molecular weight kininogen (HMWK) are the coagulation factors of the intrinsic coagulation pathway. Factor XII, high molecular weight kininogen, and prekallikrein are also called the “contact” factors. Factor XI is sometimes included in this designate of “contact” factors because of its interaction with others listed. Factor XI is activated by factor XIIa formed through activation of XII by a HMWK-prekallikrein complex on endothelial cells. With production of XIIa and kallikrein, activation of kinin, fibrinolytic, and complement systems occur. The major inhibitor of XIIa and kallikrein is C1 inhibitor. Other inhibitors include antithrombin (AT), plasminogen activator inhibitor (PAI), and α2-macroglobulin.
Contact factor deficiencies have no hemorrhagic consequence; however, the contact factors are necessary for normal aPTT clot formation in the laboratory. Deficiency of prekallikrein produces markedly prolonged aPTT results. Hereditary prekallikrein deficiency conditions are inherited through an autosomal recessive pattern. Although the aPTT is prolonged in deficiencies of factor XII, prekallikrein, and high molecular weight kininogen, there is generally no clinical evidence of bleeding unless other contributing factors are present. These deficiencies are generally diagnosed when evaluating a prolonged aPTT with no other explanation (ie, other screening test) and clinical history is negative for a bleeding disorder.
|Order Code||Order Code Name||Order Loinc||Result Code||Result Code Name||UofM||Result LOINC|
|500194||Prekallikrein Assay||500195||Prekallikrein Assay||%||52759-8|
© 2021 Laboratory Corporation of America® Holdings and Lexi-Comp Inc. All Rights Reserved.
The LOINC® codes are copyright © 1994-2021, Regenstrief Institute, Inc. and the Logical Observation Identifiers Names and Codes (LOINC) Committee. Permission is granted in perpetuity, without payment of license fees or royalties, to use, copy, or distribute the LOINC® codes for any commercial or non-commercial purpose, subject to the terms under the license agreement found at https://loinc.org/license/. Additional information regarding LOINC® codes can be found at LOINC.org, including the LOINC Manual, which can be downloaded at LOINC.org/downloads/files/LOINCManual.pdf