Clinics and Departments

Laboratory Services

Lab Dept:


Test Name:


General Information

Lab Order Codes:

TTUM (Back-up only)


Fibrin Time; Fibrinogen screen, Thrombin Time to U of M; TT

CPT Codes:

85670 – Thrombin Time, plasma

Test Includes:

Thrombin time reported in seconds.


Test Indications:

Useful at some institutions for monitoring heparin therapy or aiding in the diagnosis of disseminated intravascular coagulation (DIC), fibrinolysis, and the presence of inhibitors.

Lab Testing Section:

Coagulation - Sendouts

Referred to:

Fairview University Medical Center (Fairview/Atlas test: TT)

Phone Numbers:

MIN Lab: 612-813-6280

STP Lab: 651-220-6550

Test Availability:

Daily, 24 hours

Turnaround Time:

4 hours routine, if received during lab hours; 1 hour STAT with pre-notification; Performed Mon-Fri 0700-1600, Sat 1000-1400

Special Instructions:

A clean venipuncture is essential. Deliver immediately to the laboratory. Indicate when specimen is drawn from a line or a heparin lock. Indicate if patient is on heparin.


Specimen Type:

Whole blood


Light Blue top (Buffered Na Citrate 3.2%) tube

Draw Volume:

2.7 mL blood in a 3 mL tube (Minimum: 1.8 mL in a 2 mL tube)

Processed Volume:

Specimens will be processed at reference lab facility if received within 4 hours of collection. Otherwise, specimens need to be processed at referring facility and provide minimum of two 0.5 mL specimens frozen at -70. Follow directions below under Special Processing.


Do Not use the first 2 mL of blood collected.

Patients with hematocrit levels of >55% must have a special tube made to adjust for the hematocrit, contact laboratory for special tube.

Fill tube completely. Mix thoroughly by gentle inversion.

Special Processing:

Lab Staff:

Patients on Heparin: Unspun sample should be shipped at room temperature within 2 hours of collection. If more than 2 hours is required for transport, the specimen needs to be processed at the sending facility. See processing information below.

Patient NOT on Heparin: Unspun samples should be shipped at room temperature within 4 hours of collection. If more than 4 hours is required for transport, the specimen needs to be processed at the sending facility. See processing information below.

Specimen processing:
Spin sample collected in blue top tube(s) for 5 minutes on the
Stat Spin centrifuge, remove plasma and transfer to a 4 mL BCS sample cup(s), spin remaining plasma again for 5 minutes in the Stat Spin Centrifuge. Transfer plasma into two labeled 10x75 mL plastic tubes with a minimum of 0.5 mL in each. Freeze at -70 and send specimens on dry ice to Fairview University.

Patient Preparation:


Sample Rejection:

Improper tube; clotted blood; overfilled tubes; underfilled tubes; mislabeled or unlabeled specimens


Reference Range:

13 – 19 seconds

Critical Values:

>60 seconds


Affected by concentration and reactivity of fibrinogen, increased amounts of fibrin degradation products (FDP), and the presence of inhibitory substances, such as heparin and large amounts of fibrin degradation products. Use of this test to monitor heparin will be unreliable if hypofibrinogenemia is present or if fibrin breakdown products (FDP) have been generated by a process of DIC.


Clotting measured photo-optically after addition of exogenous thrombin.


Patients on heparin therapy


Fairview University Medical Center Web Page January 2014

Harmening DH (1997) Clinical Hematology and Fundamentals of Hemostasis


5/21/2004: Reference range updated to 13.0 – 19.0 seconds for all ages. Previously listed as 10.0 – 22.0 seconds for patients greater than or equal to one year.
Draw volume changed from 4.5 mL to 2.7 mL blood. Minimum changed from 2.7 mL to 1.8 mL blood.
5/25/2010: Tubing patient specimens is no longer prohibited.
1/13/2014: Updated specimen processing information, differentiating requirements between patients on heparin and those that are not.
2/24/2014: Updated specimen processing information from Fairview.

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