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Test Code PTINR Prothrombin Time

Important Note

Specimen tube must be full. The ratio of blood to anticoagulant is critical. Incorrect blood to anticoagulant ratio will cause erroneous results.

Please indicate if patient is on anticoagulant therapy.

Laboratory Code

LAB320

Specimen Requirements

Submit only one of the following specimens:


Specimen Type:  Whole Blood
Container/Tube: Light Blue Top (3.2% Sodium Citrate)
Volume: 2.7 mL Whole Blood (Tube must be full)
Collection Instructions: Send whole blood specimen to laboratory immediately.


Specimen Type: Platelet Poor Plasma
Container/Tube: Light Blue Top (3.2% Sodium Citrate)
Submission Container/Tube: Plastic Vial

Minimum Volume: 1.0 mL Plasma
Collection Instructions:

1. Light Blue top tube must be properly filled with whole blood.

2. Whole blood specimen should be double centrifuged and plasma separated from cells within 4 hrs of collection

3. Freeze the plasma in well-closed plastic tube immediately.

Specimen Stability

Specimen Type Whole Blood Plasma
Ambient 24 hours 24 hours
Refrigerate Unacceptable Unacceptable
Frozen Not available 14 days Clotted or insufficient

Methodology

Photo-optical Clot Detection

Days and Times Performed

24 hrs, TAT 1 day

Specimen Condition

Gross Haemolysis Reject
Icterus OK
Lipaemia OK
Others: Clotted or insufficient specimen Reject

Reference Interval

Adults 9.7 – 11.8 seconds
Venous Thromboembolism 2.0 – 3.0 INR
Mechanical Heart Valves 2.5 – 3.5 INR

Critical values: Refer to Critical Values Table

Testing Laboratory

National University Hospital
Haematology, 67725320

Useful For

Monitoring of anticoagulation therapy, e.g. Warfarin.

Screening test for clotting factor deficiency, e.g. Factor VII.

PTINR will be prolonged in disseminated intravascular coagulation, liver disease and vitamin K deficiency.

Service Code

12403

LOINC Code Information

PT 5902-2
INR 6301-6

 

Alias

INR

Protime

PT

Update

Last updated 21/03/2025