Thrombin Clotting Time (THROM)

Test Code
LAB324

Quest Code
883

CPT Codes
85670

Preferred Specimen
1 mL frozen  plasma collected in a 3.2% sodium citrate (light blue-top) tube

Minimum Volume
0.5 mL

Instructions
Collect plasma by carefully mixing 1 part 3.2% sodium citrate with 9 parts venous blood. Gently mix but do not shake. Centrifuge immediately at 1500g for 10 minutes. Remove plasma using a plastic pipette and transfer into a transport tube and promptly freeze.

Transport Container
Transport tube

Transport Temperature
Frozen

Specimen Stability
Room temperature: Unacceptable
Refrigerated: Unacceptable
Frozen: 30 days

Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Hemolysis • Received room temperature • Received refrigerated

Methodology
Clot detection using the Behring Coagulation System (BCS)

Setup Schedule
Tuesday and thursday

Limitations
Expected impact by therapeutic levels (potential interference depends upon drug concentration): Warfarin: no effect; Heparin (UFH or LMWH): prolonged; Dabigatran or Argatroban (Thrombin Inhibitors): prolonged; Rivaroxaban or Apixaban (Factor Xa Inhibitors): no effect.

Reference Range
13-19 seconds

Clinical Significance
This test, also known as thrombin time, is useful for evaluating the presence of heparin and other direct thrombin inhibitor anticoagulants in specimens with prolonged coagulation studies. It is also used to aid in the diagnosis of congenital and acquired disorders of fibrinogen [1].

Thrombin, or factor II, is a coagulation factor synthesized in the liver and activated in response to bleeding. When activated, thrombin has many roles, including the cleavage of fibrinogen into fibrin and the formation of a clot to stop the bleeding [1].

Thrombin is the target of many exogenous anticoagulant agents, including heparin (via enhancement of the activity of a protein called antithrombin) and some direct oral anticoagulants (specifically direct thrombin inhibitors) [1].

The thrombin clotting time is based on the principle that the addition of thrombin reagent to a sample should act upon fibrinogen in the sample, converting it to fibrin and forming a blood clot. The time required for clot formation is reported in seconds [1].

The thrombin time may be prolonged in the presence of exogenous heparin and direct thrombin inhibitor anticoagulants. It will also be prolonged in fibrinogen deficiencies (afibrinogenemia and hypofibrinogenemia) and fibrinogen functional disorders (dysfibrinogenemia) [1].

Many other conditions are also known to prolong thrombin clotting time, including liver failure, paraproteinemia, thrombocytopenia, platelet functional disorders, and any process that increases fibrin degradation products (FDPs), such as disseminated intravascular coagulation [1].

There are many causes of prolonged coagulation studies, and interpretation of the thrombin clotting time requires integration with other laboratory and clinical studies. This test should be interpreted in the context of pertinent clinical and family history and physical examination findings.

Reference
1. Rodak BF, et al. Hematology Clinical Principles and Applications. 4th ed. Elsevier Saunders; 2012:753-754.

Performing Laboratory
Quest Diagnostics Nichols Institute-Chantilly VA
14225 Newbrook Drive
Chantilly, VA 20151-2228




The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.