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HelpTest Code PT W INR PL Prothrombin Time (PT), Plasma
Methodology
Photometric
Includes International Normalized Ratio (INR).
Performing Laboratory
Decatur Morgan Hospital-Parkway Campus
Specimen Requirements
Specimen must arrive within 24 hours of draw.
1. Draw blood in a blue-top (citrate) tube(s). Send
specimen to laboratory within 24 hours refrigerated or at ambient
temperature.
2. If specimen is to be stored longer than 24 hours, spin down,
remove plasma, spin plasma again, and place 1 mL of citrate
platelet-poor plasma in plastic vial. (Glass vial is
not acceptable.)
Note: Double-centrifuged specimen
is critical for accurate results as platelet contamination may
cause spurious results.
3. Freeze specimen immediately at ≤-40° C, if
possible.
4. Send specimen frozen.
Note: 1. If the patient is being treated
with Coumadin®, this should be noted. Coumadin® will lower
protein C.
2. Heparin >2 U/mL may interfere with this assay.
Reference Values
PT
12.1-15.5 seconds
INR
Critical value (automatic call-back): ≥6.00
RECOMMENDED INR VALUES:
2.0-3.0
| Recommended Therapeutic Range for Oral Anticoagulant Therapy* | |
| Indication | INR |
| Prophylaxis of Venous Thrombosis (High-risk Surgery) | — |
| Treatment of Venous Thrombosis | — |
| Tissue Heart Valves | 2.0-3.0 |
| Acute Myocardial Infarction (To Prevent Systemic Embolism**) | — |
| Valvular Heart Disease | — |
| Atrial Fibrillation | — |
| Treatment of Pulmonary Embolism | — |
| Mechanical Prosthetic Valves (High-risk) | 2.5-3.5 |
|
*From Hirsh J., et al., 1995. Oral anticoagulants. In. Chest 108:4 (Supplement), p. 2311S-246S. **If oral anticoagulant therapy is elevated to prevent myocardial infarction, an INR of 2.5 to 3.5 is recommended, consistent with FDA recommendations. |
|
INR should only be used for patients on long-term (>6 weeks) Coumadin® therapy. INR should not be used when screening for factor deficiencies.
Test Classification and CPT Coding
85610