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Specimen Collection Manual and Test Catalog

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THROMBIN TIME

Geisinger Epic Procedure Code:  LAB3152    Geisinger Epic ID:  7224

SPECIMEN COLLECTION
Specimen type: 

Platelet-free plasma


Preferred collection container: 
Alternate collection container: 
Other size blue-top (3.2% sodium citrate) tubes (e.g., 1.8 mL, 4.5 mL)
Specimen required: 

1 mL aliquot plasma


Special notes: 
  • If the patient’s hematocrit (HCT) is >55%, the volume of anticoagulant in the tube must be adjusted. Contact a performing location for sodium citrate adjusted tubes or instruction for how to adjust the sodium citrate.
  • When possible, use fresh venipuncture.
  • Avoid prolong tourniquet time (< 1 minute) and hemolysis during collection as this will alter results.
  • If indwelling catheter or butterfly collection device must be used, draw sample from a non-heparinized lumen or flush the line with 5 mL of saline and discard the first 10 mL of blood.
  • Tubes should be >90% filled.
  • Immediately mix gently after collection by inverting the tube end over end 5 to 6 times. Avoid vigorous mixing or additional inversion. Observe for the presence of clots and recollect if observed.


SPECIMEN PROCESSING
Processing instructions: 

Centrifuge as soon as possible (within 60 minutes) at designated time and speed to obtain platelet-reduced or platelet-poor plasma (< 10,000/uL). Remove plasma and re-spin the plasma for 10 minutes at 3000 rpm and submit platelet free plasma.  

For a single NaCit blue top tube collection, create 1 aliquot NaCit and if additional plasma remains, create an additional aliquot NaCit. If multiple tubes collected, create 1 aliquot NaCit for each NaCIt blue top tube collected plus one additional aliquot NaCit. Aliquots should be 1.0-1.9 mL and all plasma-based coagulation tests must be moved to aliquot(s).


Transport temperature: 

Frozen on dry ice


Specimen stability: 

Room temperature (whole blood): 4 hours 
Room temperature (plasma off cells): 8 hours 
Frozen (plasma) -20°C: 2 weeks 
Frozen (plasma) -70°C: 6 months 
 


Rejection criteria: 

Clotted specimen. Overfilled or underfilled tubes. Stability limits exceeded. HCT >55% without proper adjustment of anticoagulant. Indications of thaw in transit are sample on slant in aliquot tube or in lid of tube. These samples will be run but will receive a comment of interpret results with caution as thawing suspected.



TEST DETAILS
Reference interval: 

14.7 to 19.6 seconds


Additional information: 

Anticoagulation Impact on Coagulation Tests


CPT code(s):  85670
Note: The billing party has sole responsibility for CPT coding.  Any questions regarding coding should be directed to the payer being billed.
The CPT codes provided by GML are based on AMA guidelines and are for informational purposes only.

Test includes: 

Thrombin time


Methodology: 
Mechanical clot-based
Synonyms: 

TT, thrombin clot time


Clinical significance: 

The thrombin time is typically prolonged when fibrinogen is less than 100 mg/dL or in the presence of antithrombotic substances including fibrin degradation products, paraproteins, or anticoagulation with either heparin or direct thrombin inhibitors. It can also be prolonged if the fibrinogen is biochemically abnormal or nonfunctional (dysfibrinogenmia).

Thrombin time is typically used in conjunction with fibrinogen activity, fibrinogen antigen, and replitase time assays to determine if the patient has hypofibrinogenemia (low amount of fibrinogen), dysfibrinogenemia, or the plasma contains anticoagulation with either heparin or a direct thrombin inhibitor.

Thrombin time is part of the PT/APTT mixing study panel, lupus anticoagulant profile, and thrombosis profile to determine whether anticoagulation is present.


Doctoral Director(s): 
Michelle Grant DO
Review Date:  09/03/2026

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