Sign in →

Test Code PT Prothrombin Time + INR

Important Note

If patient is on Warfarin, please order Warfarin PT.

Clinical System Name

Prothrombin Time + INR
 

Synonyms

INR
Protime
PT
PT INR

Description

The prothrombin time is a basic coagulation screening test for the assessment of congenital and acquired deficiencies of the extrinsic pathway (factors II, V, VII, X). The prothrombin time can be prolonged in certain clinical states, i.e. warfarin therapy, intestinal reabsorption disorders, liver failure, fibrinolysis and DIC.

Sample Requirements

Specimen: Whole Blood

Container(s): Lt Blue/Citrate

Preferred Vol: 1.8 mL

Minimum Vol: N

 

Note:  Preferred method of collection is venipuncture with vacuum fill.  Test results are affected by incorrect blood volume, note the fill line on the tube.  Use of a Vascular Access Device for the  collection of coag testing is not recommended.

If this method is used it requires a 5 mL waste volume; 3 mL for size 2 French catheter or smaller. Blood must be trasferred to the  Lt Blue/Citrate tube by use of a  blood transfer device to ensure proper fill. 

Specimen should be centrifuged within 1 hour of collection.

Processing Instructions

Reject due to: Clotted, Hemolyzed, Insufficient quantity, and  Improper collection.

Spin:N

Aliquot:N

Temp:RT

Storage location: Core 6 Freezer  ( -70 C).

 

Note: Deliver blood to Core Coag bench.  Coag Technologist will process. Specimen should be centrifuged within 1 hour of collection. Spin whole blood, remove plasma. Transfer upper 3/4 layer of plasma to plastic tube affixed with large computer label.

 

 

 

Off-site collection:Preferred method of collection is venipuncture with vacuum fill. Test results are affected by incorrect blood volume, note the fill line on the tube. Use of a Vascular Access Device for the collection of coag testing is not recommended. If this method is used it requires a 5 mL waste volume; 3 mL for size 2 French catheter or smaller. Blood must be trasferred to the Lt Blue/Citrate tube by use of the blood transfer device.

Specimen should be centrifuged within 1 hour of collection. Double spin, transfer upper 3/4 layer of plasma to plastic tube affixed with large computer label. Freeze 2 aliquots of 1.0 mL plasma in plastic tubes at -70C.

Ship frozen on dry ice.

.

Stability

Specimen Type Temperature Time
Citrated platelet-poor plasma Room temp N
  Refrigerated N
  Frozen   -20 C or -70 C 3 m

 

Availability

STAT Performed TAT
Y

Daily

1 h

 

Performing Laboratory

Seattle Children's Laboratory    

 

Department

Department:  Coagulation

Phone Number: 206 987-2578

 

 

 

Reference Range

 

 

 

Age Seconds

Less than 3 months

12.5 -17.0
3 months or Older 12.5 - 15.2

 

Methodology

Method:  Electromagnetic mechanical clot detection system by STA® - Compact Analyzer

Analytical Volume: 1 mL plasma

This is enough for a PT, PTT, TT, and Fibrinogen on the same sample.

 

Limitations: Method is affected by improper collection, processing and storage.

High hematocrit greater than or equal to 56% requires a citrate adjusted tube.

CPT Codes

85610

Critical Values

Age Seconds
Less than 3 months greater than 30
3 months or Older greater than 30