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*Prothrombin Time-INR

Mnemonic

PT-INR

Synonym

PT-INR - PT - Protime - Prothrombin Time - International Normalized Ratio

Specimen Collection Requirements

Collect

Whole Blood light blue (3.2% Buffered Sodium Citrate) top tube

(View image for Supply Item Number - 238095)

Handling

See Coagulation Specimen Collection Guidelines. Whole blood specimen tubes must reach the testing department within 24 hours, otherwise submit frozen plasma aliquots. NOTE: Frost-free refrigerator freezers are not acceptable for frozen sample storage. If proper storage is unavailable at the collection site, freeze/store aliquots on dry ice. Alternatively, send the patient to the nearest Legacy Hospital Outpatient Lab for sample collection/processing.

If submitting whole blood, transport at ambient temperature (15-25°C) in original unopened tube. If submitting frozen plasma aliquots, specimens must remain frozen (-20°C) during transport. Protime/INR specimens should never be refrigerated.

Preferred Volume

2.7 mL whole blood or two 1.0 mL frozen plasma aliquots

Minimum Volume

1.8 mL whole blood or one 1.0 mL frozen plasma aliquot

Transport

Whole Blood: Ambient (15-25°C)

Plasma: Frozen, aliquot must remain frozen during storage and shipment

Protime/INR specimens should never be refrigerated.

Rejection Criteria

Refrigerated whole blood or plasma
Clotted samples, samples collected in containers other than 3.2% Buffered Sodium Citrate, tubes filled less than 90%, samples from patients with a Hematocrit greater than 55%, hemolyzed samples due to ex-vivo causes (i.e., difficult draw, poor sample draw), whole blood samples that were frozen before processing

Stability

WHOLE BLOOD: Ambient: 24 hours 
PLASMA: Ambient: 4 hours; Frozen (-20°C): 2 weeks, Frozen (-70°C): 6 months

Testing Information

Performed

7 days/week

Reported

24 hours

Method

Clotting

Reference Values

Reference Values

Varies, see report.

Critical Values

INR: ≥5.0

Therapeutic Range

Refer to Anticoagulant Therapy Monitoring
 

While rare, INR discrepancies have been observed in the following, combined circumstances: 

1. When the previous INR was reported by a non-Legacy Lab using a different PT reagent, and the INR is greater than 4.0. 

2. The patient is unstably anticoagulated, and has concurrent comorbid factors (i.e., liver disease, sepsis, etc.). This appears to be the biggest factor.

CPT Codes

85610

Last Updated: Wednesday, December 30, 2020 02:09:36 AM


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