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St. John Health System
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Prekallikrein (Fletcher Factor) Activity

Order Name PREKALL
Test Number: 6905123
Revision Date 12/12/2022
Test Name Methodology LOINC Code
Prekallikrein (Fletcher Factor) Activity
Electromagnetic Mechanical Clot Detection 52759-8 
SPECIMEN REQUIREMENTS
Specimen Specimen Volume (min) Specimen Type Specimen Container Transport Environment
Preferred 2 mL (1 mL) Platelet Poor Plasma Sodium Citrate 3.2% (Blue Top) Frozen
Instructions Specimen Type: Blue-top (sodium citrate) tube
Specimen Storage: FROZEN
Specimen 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 anti- coagulant 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.[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 recentifuge for 10 minutes. Use a second plastic pipette to remove 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 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.
Special Instructions: Testing is performed at Esoterix Coagulation Laboratory: UY#300121
Specimen Stability:  Room temperature up to 4 hours
GENERAL INFORMATION
Expected TAT 4 - 8 days 
Notes 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.
?Labcorp Test Code: 500194
CPT Code(s) 85292
Internal Comments Bulk Load by PS and JK 4/11/2017
Service Provided By Labcorp Oklahoma, Inc.
Lab Section Reference Lab