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Test Code PTIN or LAB320 Prothrombin Time (PT/Protime) with International Normalized Ratio (INR), Blood

Important Note

Please contact the laboratory if the patient's hematocrit is over 55%, as a special tube must be provided for the blood draw.

Specimen Requirements

Specimen Type:

Whole Blood

Container Type:

Blue top: 2.7 mL or 1.8 mL

Optimal Collection Volume:
  • 2.7 mL in solid blue top tube or 1.8 mL in clear blue top tube.  The correct fill volume is indicated by the etched line on the tube.
  • Click here to view the specimen collection guide for blue top (citrate) tubes.

Collection Instructions:
  1. Gently invert 5 to 10 times to mix blood.
  2. If collected through a blood collection set (butterfly), a discard tube must first be drawn to eliminate dead space from tubing.  

Specimen Transport Temperature:
  • Room temperature up to 24 hours. If testing is delayed, separate plasma and freeze (see outpatient collection instructions below).
  • Specimens cannot be refrigerated

Processing Instructions:

 

  1. Centrifuge sample if testing will not be performed with in 24 hours. Platelet-poor plasma must be obtained per laboratory procedure.
  2.  Aliquot plasma into a separate vial and freeze immediately.

Outpatient collections

  1. Spin down the sample, remove plasma, and spin plasma again to obtain platelet-poor plasma.
  2. Separate the platelet-poor plasma into a screw-top vial.
  3. Freeze plasma immediately.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Specimen Stability

Specimen Type

Temperature

Time

Whole blood

Room Temperature

24 hours

Platelet Poor Plasma

Room Temperature

24 hours

Platelet Poor Plasma

Frozen at -20 C

2 weeks

Specimen Rejection Criteria

  • Tube underfilled
  • Refrigerated specimen
  • Clotted specimen

Useful For

  • Screening for coagulation deficiencies
  • Monitoring test for oral anticoagulant therapy

Methodology

ACL TOP - Coagulometric (Turbidimetric)

Reference Ranges

Test Name

Reference Range and Reporting Units

Protime

The reference range for seconds will vary with each lot number of reagent. See individual patient reports for the current seconds reference range.

INR

The following therapeutic ranges are recommended:

  • 2.0-3.0: Anticoagulation for prophylaxis and treatment of venous thrombosis, pulmonary and systemic embolism, and bioprosthetic heart valve.
  • 2.5-3.5: Anticoagulation for mechanical heart valve or postmyocardial infarction.

 

Critical Value: INR ≥ 5.0

Day(s) Performed

24/7

Expected TAT

Same day

Performing Laboratory

Bronson Laboratory, Coagulation - Kalamazoo, Battle Creek, Paw Paw, South Haven

Sample Retention Time

48 hours

CPT Code

85610

LOINC Code

5964-2