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Test Code PTT Partial Thromboplastin Time

Important Note

Direct outpatients to a hospital outpatient collection laboratory.  Testing must occur within 4 hours of collection or sample must be frozen.

EHR Test Codes

  Test Code Test Name
Atlas PTT PTT
Cerner PTT Partial Thromboplastin Time

 

Specimen Requirements

Preparation of Patient: 

None

 

Container Type:

Light Blue Top 3.2% Sodium Citrate Tube 4.5 mL, 3.0 mL, 2.7 mL, 2.0 mL, or 1.8 mL

Specimen Type:

Plasma platelet poor

 

Specimen Volume:

Fill tube completely.  Less than 90% filled tubes will be rejected.

 

Special Instructions:

For patients who are difficult access, < 1 year, and/or have a hematocrit > 55.9%; special tubes with an adjusted amount of anticoagulant can be prepared to allow for proper blood/anticoagulant ratio for accurate testing.  Call the Hematology lab at 231-935-6118 to request special tube.

 

Specimen Handling/Transport:

Do not centrifuge.  Do not refrigerate.  Deliver to laboratory immediately.

Transport ambient room temperature.

 

Special Instructions: 

If a specimen cannot be tested within 4 hours of draw, plasma should be removed from the cells and preserved as follows: Spin in a centrifuge verified for platelet-poor plasma preparation, remove plasma to a plastic tube, spin the plasma a second time, then remove plasma to a screw-top plastic  tube and freeze immediately at -20° C. Transport frozen.

 

Specimen Storage/Stability:

Whole blood ambient room temperature 4 hours. 

Double spun plasma aliquot ambient room temperature 6 hours.

Double spun plasma aliquot frozen -20° C 3 months.

 

Specimen Rejection:

Less than 90% filled tubes

Hemolysis

Clotted

Performing Laboratory

Munson Healthcare Laboratories

Priority, Frequency, & Turnaround

Priority:

STAT, ASAP, Non-Emergent

 

Frequency:

24 hours 7 days a week

 

Turnaround:

0 - 1 days

STAT 60 minute from receipt in lab

Methodology

Electromagnetic Mechanical Clot Detection System

Reporting

Reference Range:

24 -36 sec
 

Critical Decision: 

0 years to 21 years  ≥ 65 sec

21 years and up  ≥ 150 sec

Note:  Critical values are called to the provider and communicated as critical.  Documentation of the call is recorded in the patient record.

Clinical Significance

The activated partial thromboplastin time is a screening test used to measure the intrinsic pathway of coagulation. The test will be prolonged if factor(s) of the intrinsic pathway (XII, XI, IX, VIII) or the common pathway (I, II, V, X) are not present in adequate concentration (approximately 35-60% of normal). Inhibitors to any of these factors will also prolong the aPTT. Nonspecific inhibitors, i.e., lupus anticoagulant, will often prolong the aPTT. Liver disease may prolong the aPTT due to decreased synthesis of factors and decreased clearance of activators of the fibrinolytic system. DIC prolongs the aPTT by consumption of Factors I, II, V, and VIII, and by elevating levels of fibrin split products which inhibit fibrin formation. Anticoagulant therapy (heparin or coumarin) may prolong the aPTT. The aPTT is useful in monitoring heparin therapy.

CPT Code(s)

85730