Home
HelpTest Code LAB3553 Warfarin Prothrombin Time + INR
Clinical System Name
Warfarin Prothrombin Time + INR
Synonyms
LAB3553
WARF PT
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 WARF 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. Use of a Vascular Access Device for the collection of coag testing is not recommended.
If this method is used it requires a 5 cc clearing volume; 3 cc 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 WARF 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
Reference range determined by provider.
Description
The Warfarin PT test is used to monitor patients receiving Warfarin therapy.
Critical Values
| Critical INR | Critial PT |
| Less than or equal to 1.5 or greater than or equal to 4.0 | >39.2 s |