Thrombin Time - Human

CPT: 85670
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Expected Turnaround Time

7 - 10 days


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Specimen Requirements


Specimen

Plasma


Volume

1 mL


Minimum Volume

0.5 mL


Container

Blue-top (sodium citrate) tube


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 N° 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.


Storage Instructions

Freeze. Stable at room temperature for four hours, refrigerated eight hours, and frozen for 13 months. Freeze/thaw cycle x5


Patient Preparation

No special patient preparation is necessary.


Causes for Rejection

Severe hemolysis; improper labeling; clotted specimen; specimen diluted with IV fluids; samples thawed in transit


Test Details


Use

Evaluation of both bovine and human thrombin times may be useful in the evaluation of antibody development in patients that have been exposed to topical bovine thrombin agents. Prolongation of the bovine but not human thrombin time may be seen in this instance. Prolongation of the thrombin time, in general can indicate an abnormality of fibrinogen and can allso occur with drugs that act as thrombin inhibitors.


Limitations

Samples that are partially clotted (micro-clots) should not be tested. Samples that may have been contaminated by heparin (in collection tubes, syringes, etc.) should not be tested, as results may be artificially prolonged.


Methodology

One-stage clotting assay using human thrombin rather than bovine thrombin


Footnotes

1. Adcock DM, Kressin DC, Marlar RA. Effect of 3.2% vs 3.8% sodium citrate concentration on routine coagulation testing. Am J Clin Pathol. 1997 Jan; 107(1):105-110.8980376
2. Reneke J, Etzell J, Leslie S, Ng VL, Gottfried EL. Prolonged prothrombin time and activated partial thromboplastin time due to underfilled specimen tubes with 109 mmol/L (3.2%) citrate anticoagulant. Am J Clin Pathol. 1998 Jun;109(6):754-757.9620035
3. National Committee for Clinical Laboratory Standardization. Collection, Transport, and Processing of Blood Specimens for Coagulation Testing and General Performance of Coagulation Assays; Approved Guideline. 5th ed. Villanova, Pa: NCCLS; 2008. Document H21-A5:28(5).
4. Gottfried EL, Adachi MM. Prothrombin time and activated partial thromboplastin time can be performed on the first tube. Am J Clin Pathol. 1997;107(6):681-683.9169665
5. McGlasson DL, More L, Best HA, Norris WL, Doe RH, Ray H. Drawing specimens for coagulation testing: Is a second tube necessary? Clin Lab Sci. 1999 May-Jun;12(3):137-139.10539100

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
504475 Thrombin Time - Human 3243-3 504359 Thrombin Time - Human sec 3243-3

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