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PROTHROMBIN TIME (Protime) with INR
Message- Tube MUST be full for proper whole blood to anticoagulant ratio. See Additional Information below.
- Requires platelet-poor plasma; see Additional Information below for instruction.
- If a butterfly needle is used for collection, a NON-ADDITIVE discard tube must be drawn first
Test Code
PT
CPT Codes
85610
Includes
Protime and INR result will be provided
Preferred Specimen
1 Blue tube (Sodium Citrate)
Minimum Volume
0.5 mL platelet-poor plasma
Requires platelet-poor plasma; see Additional Information below for instruction.
Requires platelet-poor plasma; see Additional Information below for instruction.
Other Acceptable Specimens
None
Instructions
PT and PTT can be performed on a single blue top tube. If ordered together, the preferred sample handling is to centrifuge and aliquot platelet-poor plasma into a transfer tube then freeze. Whole blood or plasma maintained at room temperature will be accepted for non-therapeutic patients only.
Transport Temperature
Frozen Plasma
For Non-therapeutic patients only: Room temperature whole blood or plasma
For Non-therapeutic patients only: Room temperature whole blood or plasma
Specimen Stability
- Frozen -20C Plasma is stable - Preferred
- Room Temperature, whole blood or plasma, 15-30C up to 24 hours (Non-therapeutic patients only)
- Refrigerated, 2-8C plasma will be tested for viability by technical staff - not recommended.
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
The following criteria will result in a rejection:
- Hemolyzed samples
- Clotted sample
- Citrate tube underfilled or overfilled
- Sample received more than 24 hours after collection (has not been centrifuged and plasma frozen)
- Whole blood or plasma that has been refrigerated
Methodology
Photo-Optical Clot Detection
Setup Schedule
M, T, W, Th, F, Sa, Sun
Report Available
​Within 24 hours of receipt at the performing laboratory. Stat testing is available.
Reference Range
PT, Non-therapy 10.1 - 13.1 seconds
0.9 - 1.1 INR
INR: 2.0-3.0 conventional anticoagulation
INR: 2.5-3.5 intensive anticoagulation
For additional information regarding specific clinical
scenarios, duration of anticoagulant therapy and combination
therapy with other anticoagulants, please refer to the
American College of Chest Physicians Evidence-Based Clinical
Practice Guidelines available at: www.Chestnet.org.
Clinical Significance
Used to screen for defects of the extrinsic & common coagulation pathways. If blood is drawn from an indwelling catheter, the line should be flushed with saline and the first 5ml of blood discarded.
Performed By
Alverno Laboratories
Performing Laboratory
Alverno Central Lab
NHMC (Hematology, IL Coag)
Additional Information
Obtaining Platelet Poor Plasma
BD Vacutainer Plus Blue-Top Volume Guide
Last Updated: April 23, 2026
