Thrombin Mixing Study

TEST: 117170
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CPT: 85670 If reflex testing is performed, concomitant CPT codes/charges will apply.
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Synonyms

  • Thrombin Clotting Time (TCT)

Test Includes

Thrombin time; reflex to thrombin time 1:1 mix and thrombin neutralization

Expected Turnaround Time

2 - 3 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.

Related Information

Related Documents

For more information, please view the literature below.

Procedures for Hemostasis and Thrombosis: A Clinical Test Compendium

Specimen Requirements

Specimen

Plasma, frozen

Volume

2 mL

Minimum Volume

1.0 mL (Note: This volume does not allow for repeat testing.)

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 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.

Storage Instructions

Freeze.

Patient Preparation

Avoid warfarin (Coumadin®) therapy for two weeks and heparin therapy for two days prior to the test. Do not draw from an arm with a heparin lock or heparinized catheter.

Causes for Rejection

Gross hemolysis; clotted specimen; frozen specimen thawed in transit; improper labeling

Test Details

Use

Help to determine the presence of an inhibitor.

Methodology

Human thrombin is mixed with the patient sample and clotting time is determined photometrically. When the thrombin time is extended, the test plasma is mixed 1:1 with normal platelet-free plasma and a TT is performed on the mixture. This serves to distinguish fibrinogen deficiency from something inhibiting fibrin polymerization. Heparin neutralization is also performed to rule out heparin as the cause of the extended TT.

Additional Information

Thrombin time will be extended when functional fibrinogen levels are <100 mg/dL.6,7 This can occur due to congenital conditions including afibrinogenemia (complete lack of fibrinogen), hypofibrinogenemia, and in dysfibrinogenemia, a condition characterized by the presence of dysfunctional fibrinogen. Acquired conditions which can lead to diminished fibrinogen levels and extended thrombin times include liver disease, renal disease, disseminated intravascular coagulation (DIC), amyloidosis, malignancy, and thrombolytic therapy.6 Thrombin inhibitors including heparin, argatroban, and hirudin will cause and extended thrombin time.7

If the TT on the 1:1 mixture is corrected to normal or near normal, fibrinogen deficiency or dysfunction may be confirmed by the combination of the clot-based fibrinogen activity assay and the fibrinogen antigen immunoassay.6 Failure of the 1:1 mix to correct suggests the presence of an inhibitor. Heparin can be ruled out through the addition of a heparin neutralizer. If no heparin is present, a fibrinogen activity and fibrinogen antigen may be used to confirm and quantitate afibrinogenemia, hypofibrinogenemia, and dysfibrinogenemia. If disseminated intravascular coagulation (DIC) is suspected, D-dimer and/or FDP assays may be used.6 If a bovine thrombin (anti-IIa) inhibitor is suspected, a thrombin time using human-derived thrombin as the reagent should be performed.6 If a paraprotein disorder is suspected, a serum protein electrophoresis may be performed.6

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 Jun; 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
6. Adcock DM, Bethel MA, Macy PA. Coagulation Handbook. Aurora, Colo: Esoterix−Colorado Coagulation; 2006.
7. Van Cott EM, Laposata M. Coagulation. In Jacobs DS, DeMott WR, Oxley DK, eds. Laboratory Test Handbook With Key Word Index. Hudson, Ohio: Lexi-Comp; 2001:327-358.

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
117170 Thrombin Mixing Study 3243-3 109009 Thrombin Time sec 3243-3
Reflex Table for Thrombin Time
Order Code Order Name Result Code Result Name UofM Result LOINC
Reflex 1 117110 TT Mix+TTN 117171 Thrombin Time Mix sec 33525-7
Reflex Table for Thrombin Time
Order Code Order Name Result Code Result Name UofM Result LOINC
Reflex 1 117110 TT Mix+TTN 117203 Thrombin Neutralization sec 46224-2

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