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Prothrombin with INR and Partial Thromboplastin Times

Test Code


CPT Code(s)

85610, 85730


INR • Prothrombin Time • PTT

Preferred Specimen(s)

1 blue top tube properly filled (min vol: 4 mL) (3.
2% Na Citrate) OR 2 mL (min vol: 1 mL) frozen Platelet
Poor Plasma from a properly filled blue top tube Label
plastic tube Frozen Citrated Plasma.
Instructions: Fill at least to the top of the
manufacturer's label, but below bottom of the blue cap.
If using a butterfly collection kit, you must draw a red
top tube first to prime the line.
Under or over filling will result in test cancellation due
to inappropriate anticoagulant to blood ratio.
**PT Stability Limit After Collection** Unopened
collection tube with vacuum intact is stable for up to 48
hours room temperature, otherwise separate and freeze
*PTT Stability Limit After Collection* Unopened collection
tube with vacuum intact is stable for up to 24 hours room
temperature, separate and freeze plasma.
**PT or PTT Open Tube Stability** Opened collection tube
is stable for 4 hours room temp, otherwise separate and
freeze plasma.
Frozen samples are stable for 2 hours when thawed.
For non-heparinized patients, maintain specimen at room
temperature and is stable 24 hours.
Do not uncap.
For heparinized patients or if testing will be delayed
longer than 24 hours, centrifuge specimen within 1 hour of
collection at 2500-3500 rpm.
Transfer citrate plasma to a plastic vial and freeze at
-20C immediately.
Specimen Stability: .
Na Citrate Blue Top Tube (Whole Blood): .
Protime PTT Room Temp: 48 hours 24
hours Refrig: Unacceptable Unacceptable Frozen:
Unacceptable Unacceptable .
Citrated Platelet Poor Plasma in Plastic Tube: .
Protime PTT Room Temp: 2 hours 2
hours Refrig: 4 hours 4 hours Frozen: 14 days
14 days.

Transport Container

Whole blood: 3.2% sodium citrate (light-blue) tube. Plasma: Plastic screw-cap vial (frozen)

Transport Temperature

Room temperature

Specimen Stability

Room temperature: 24 hours
Refrigerated: 24 hours
Frozen: 7 days


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.