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Test Code LAB4017 Partial Thromboplastin Time (PTT)

Important Note

Tube must be filled completely to maintain correct Anticoagulant/Blood ratio.

Specimen must be tested or frozen within 4 hours of draw.

Additional Codes

Labcorp 005207

Specimen Type

Blue top tube (buffered 3.2% liquid sodium citrate) filled to the indicator with whole blood or Sodium Citrate Plasma removed from cells.

Specimen Volume

3mL Blue top (3.2% Sodium Citrate)
5mL Blue top (3.2% Sodium Citrate)
1mL Blue top (3.2% Sodium Citrate)
500uL (minimum) Sodium Citrate Plasma spun and removed from cells.

Turnaround Time

STAT: 1hr
Routine: 2-4 hours

Test Schedule

Daily

Sample Stability

Non-heparin Patients: 4 hours, spun or unspun
Patients on heparin: 1 hour unspun, 4 hours spun. Platelet poor plasma required.
Frozen samples are stable for 2 weeks at -20C or 12 months at -70C.

Method

Electromechanical

Reference Ranges

PTT 23.5 – 34.6 seconds

Synonyms

Partial Thromboplastin Time; APTT

CPT Codes

85730

Test Components

PTT, sec

Specimen Processing

Assays of non-heparinized patients must be performed within 4 hours of collection. Assays on specimens suspected to contain unfractionated heparin therapy should be tested within 1 hour of collection.  If time interval between drawing and testing exceeds 1 hour, process sample to create platelet poor plasma, separate into plastic tube and freeze at -20C or less. Frozen samples are stable for 2 weeks at -20C or 12 months at -70C.

Clinical Information

The activated partial thromboplastin time (aPTT) is a basic screening test for activity of the intrinsic coagulation pathway (factors XII, XI, IX, VIII, X, V, II, and fibrinogen). A prolongation of the aPTT may be seen in the following deficiencies: Factors VIII, IX, XI, XII, pre-kallikrein and high molecular weight kininogen. Abnormal aPTT may also be seen in liver disease; disseminated intravascular coagulation (DIC); circulating anticoagulants such as Lupus Anticoagulant or a specific factor inhibitor; during heparin or oral anticoagulant therapy; and when treated with direct thrombin inhibitors (hirudin, Argatroban, etc.).