Health Lab

Test Name:

PROTHROMBIN TIME (PT)

Test Code:

2180056

Alias:

INR
LAB320
Prothrombin Time Assay
Protime
PT

CPT Code(s):

85610

Test Includes:

Prothrombin Time (PT) and International Normalized Ratio (INR)

*This CPT code is subject to a Medicare Limited Coverage Policy and may require a signed ABN when ordering.

National Coverage Determination (NCD) for Prothrombin Time (PT): https://www.cms.gov/medicare-coverage-database/details/ncd-details.aspx?NCDId=80&ncdver=1&bc=AgEAAAAAAAAA

Preferred Specimen:

1 - full (see fill line on tube) Sodium Citrate (lt blue)

Container:

Sodium Citrate (lt blue)

Minimum Volume:

1 - full (see fill line on tube) Sodium Citrate (lt blue) tube or 1.0 mL frozen platelet-poor plasma

Collection Instructions:

Invert tube 5 to 10 times immediately after filling and transport at room temperature (stable for 24 hours). To increase stability, send frozen platelet-poor plasma.

For frozen platelet-poor specimens: Centrifuge the specimen for 15 minutes within 1 hour of collection. Using a plastic pipette, remove the plasma taking care to avoid the WBC/platelet buffy layer and transfer the plasma into a properly labeled transfer tube. Centrifuge the transferred plasma a second time and transfer platelet-poor plasma into a new properly labeled transfer tube. Label tube as "platelet-poor". Freeze immediately and transport to the lab frozen.

Transport Temperature:

Room temperature or frozen (refer to stability times)

Stability:

Room temperature: 24 hours
Refrigerated: unacceptable

Frozen: 14 days (platelet-poor plasma only)

Rejection Criteria:

Hemolysis
Clotted
Underfilled tube

Limitations:

Values obtained with different assay methods should not be used interchangeably in serial testing. It is recommended that only one assay method be used consistently to monitor each patient's course of therapy.

Additional Information:

Blood should be collected in a blue-top tube containing 3.2% buffered sodium citrate. Evacuated collection tubes must be filled to completion (see fill line on tube) to ensure a proper blood-to-anticoagulant ratio. Submit difficult draws in pediatric tube (0.5 mL frozen platelet-poor plasma). The sample should be mixed immediately by gentle inversion to ensure adequate mixing of the anticoagulant with the blood.

Schedule:

Set up: Daily; Results in 24 hours

Method:

Optical clot detection

Clinical Significance:

Prothrombin time is used for the evaluation of the extrinsic coagulation pathway and the monitoring of oral anticoagulant therapy (OAT).

Use:

Updated 1/5/24

Reference Range Table

Result	Units	Gender	Age	Range
PROTHROMBIN TIME (PT)	seconds	Both	0 Year - 999 Year	10.5-13.5
INTERNATIONAL NORMALIZED RATIO (INR)		Both	0 Year - 999 Year	0.8-1.2

The CPT codes included in this publication are in accordance with Current Procedural Terminology, a publication of the American Medical Association. CPT codes are provided here for the convenience of our clients; however, correct coding often varies from one carrier to another, and HealthLab may bill specific carriers using codes other than those shown. Clients who bill for services should verify the code(s) with the applicable payor to confirm that their use is appropriate in each case.