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Prothrombin with INR and Partial Thromboplastin Times

Test Code


CPT Code(s)

85610, 85730

Preferred Specimen(s)

One full unopened 3.2% sodium citrate (light blue-top) tube

Alternative Specimen(s)

1 mL frozen plasma: If the specimen will be delayed longer than 48 hours, centrifuge specimen for 15 minutes at 2500-3500 rpm. Using a plastic pipette, remove plasma, taking care to avoid the WBC/platelet (buffy) layer and place into a plastic screw-cap vial and freeze at -20° C. Ship on dry ice.

Collection Instructions

Correct ratio of blood to citrate is critical. Do not overfill or underfill collection tube. Mix by inversion 4 times. For non-heparinized patients, maintain specimen at room temperature. Do not uncap. Stable 24 hours at room temperature.

Transport Container

3.2% sodium citrate (light blue-top) tube

Transport Temperature

Room temperature

Specimen Stability

Unopened light blue-top tube
Room temperature: 24 hours
Refrigerated: Unacceptable
Frozen: Unacceptable

Separated platelet-poor plasma
Room temperature: 2 hours
Refrigerated: 4 hours
Frozen -20° C: 14 days
Frozen -70° C: 6 months

Reject Criteria

Gross hemolysis • Gross lipemia • Improper blood to citrate ratio • Clotted • High hematocrit • Improper blood collection


Photo-optical Clot Detection

Setup Schedule

Set up: Daily; Report available: 1 day


PT/INR: Expected impact by therapeutic levels (potential interference depends upon drug concentration): Warfarin: prolonged; Heparin (UFH or LMWH): little to no effect (reagent contains a heparin neutralizer); Dabigatran or Argatroban (Thrombin Inhibitors): normal to prolonged; Rivaroxaban or Apixaban (Factor Xa Inhibitors): prolonged.

aPTT: Expected impact by therapeutic levels (potential interference depends upon drug concentration): Warfarin: prolonged; Heparin (UFH or LMWH): prolonged; Dabigatran or Argatroban (Thrombin Inhibitors): prolonged; Rivaroxaban or Apixaban (Factor Xa Inhibitors): prolonged.

Reference Range(s)

PT 9.0-11.5 sec
  Reference range 0.9-1.1
  Moderate - intensity Warfarin therapy 2.0-3.0
  Higher - intensity Warfarin therapy 3.0-4.0
aPTT 22-34 sec

Clinical Significance

PT/INR: Screening test for abnormalities of coagulation factors that are involved in the extrinsic pathway. Also used to monitor effects of Warfarin therapy and to study patients with hereditary and acquired clotting disorders.

aPTT: The aPTT is a screening test that will detect deficiencies or inhibitors to the intrinsic (Factors VIII, IX, XI and XII) and common (Factors II, V, X and Fibrinogen) pathway coagulation factors.

LOINC®' Code(s)

The Result and LOINC information listed below should not be used for electronic interface maintenance with Quest Diagnostics. Please contact the Quest Diagnostics Connectivity Help Desk for more information at 800-697-9302.

NOTE: The codes listed in the table below are not orderable Test Codes.

Result NameLOINC CodeComponent Name
INRINR6301-6Coagulation tissue factor induced.INR
PTPT5902-2Coagulation tissue factor induced
PTTPTT14979-9Coagulation surface induced

Reference ranges are provided as general guidance only. To interpret test results use the reference range in the laboratory report.

The CPT codes provided are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payer being billed.

LOINC assignment is based on a combination of test attributes, including the method used by the performing laboratory. For tests not performed by Quest Diagnostics, codes are assigned by the performing laboratory.

* The tests listed by specialist are a select group of tests offered. For a complete list of Quest Diagnostics tests, please refer to our Directory of Services.