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HelpTest Code LAB320 Prothrombin Time + INR
Clinical System Name
Prothrombin Time + INR
Synonyms
LAB320
INR
Protime
PT
PT INR
Sample Requirements
Specimen: Whole Blood
Container(s): Lt. Blue/Citrate
Required Vol: one 1.8 mL tube or one 2.7 mL tube (do NOT over or under fill)
Minimum Vol: N
Note: This is enough for a PT, PTT, TT, and Fibrinogen on the same sample. 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 transferred 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
Main Campus CPA: Core Technologist will process specimen. Deliver blood directly to Core Coag bench.
Reject due to: Clotted, Insufficient quantity (underfill), or Improper collection (overfill).
Spin: Y
Aliquot: Y
Storage location: Core 14 Freezer ( -70 C).
Core Technologist: 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 transferred 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 until solid one aliquot of 1.0 mL plasma in plastic tube at -70C (preferred) or -20C.
Non-Children's Hospital Off-site collection: Ship completely frozen on dry ice.
Children's Regional Clinics: Ship completely frozen in frozen Nalgene Labtop cooler with ice pack inside an insulated soft cooler.
Stability
| Specimen Type | Temperature | Time |
|---|---|---|
| Citrated platelet-poor plasma | Room temp | ≤4 h |
| 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: 206 987-2617 (Client Services)
CPT Codes
85610
Methodology
Method: Electromagnetic mechanical clot detection system by STA-R MAX
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.
Reference Range
| Age | Seconds |
|
Less than 3 months |
12.5 - 17.0 |
| 3 months or Older | 12.5 - 15.2 |
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.
Critical Values
| Age | Seconds |
| Less than 3 months | greater than 30 |
| 3 months or Older | greater than 30 |