Pathology | Eastern Health

Test & Collection Guide

Prothrombin Time

Ordering information:

Warfarinsied outpatients can use a "Rule 3 Exemption" request to allow multiple INR collections to be made using the one request form.

Please click here for a link to the Rule 3 Exemption Request Form
Please click here for a link to the Warfarin Dosing Referral Form

Alternate names:

DINR, INR, PT

Laboratory:

Coagulation

Test Code:

INR, DINR

Specimen types:

Plasma

Container types:

Sodium Citrate

Collection Instructions:

Transport specimen at Room Temperature to lab

Filled to label marker and mixed by inversion.

Patient Information - Warfarin Management-English
Patient Information - Warfarin Management-Greek
Patient Information - Warfarin Management-Simplified Chinese

Frequency:

Daily

Result Turnaround Time:

2 hours

Reference Interval:

Prothrombin Time: 10 - 15 seconds

Prothrombin Time is expressed as the International Normalised Ratio (INR):

Prophylaxis for atrial fibrillation	2.0 - 3.0	INR
Treatment of deep vein thrombosis	2.0 - 3.0	INR
Tissue heart valve replacement	2.0 - 3.0	INR
Mechanical heart valve replacement	2.5 - 3.5	INR
Anti-phospholipid syndrome	2.0 - 3.0	INR

Laboratory Use Only

Storage Instructions:

Specimens must not be analysed more than 8 hours following collection unless the patient is receiving warfarin therapy (INR) where analysis may be performed up to 24 hours post collection provided that the sample is stored at room temperature and had not been refrigerated. Freshly separated plasma can be used if stored at, or below, -20 ºC for up to three months.