Specimen Collection

2.7 mL Citrate Blood

or

1.8 mL Citrate Blood

or

1 mL Paediatric Micro-citrate Blood

• Tube must be adequately filled.

Reference Intervals

Normal Reference Interval

0 - 4 days	0.9- 1.3
Full term neonate	adult level by day 5
Adult	0.8 - 1.2

Therapeutic range see

International Normalised Ratio

Uncertainty of Measurement : 4%

Turnaround Time: Within 2 hours
Diagnostic Use and Interpretation

This test is used to screen for inherited or acquired abnormalities in the extrinsic (Factor VII) and common (Factors V, X, prothrombin and fibrinogen) pathways.

Prothrombin Ratio = (Clotting time test plasma) / (Mean normal prothrombin time)

Interpretation

Raised Prothrombin Ratio: Commonest causes are:

• oral anticoagulant therapy
• vitamin K deficiency and liver disease
• deficiency or inhibitor of individual factors
• premature neonate

The presence of a normal echis ratio with a raised PR helps differentiate warfarin/vitamin K deficiency from other causes of a raised PR.

Lowered Prothrombin Ratio:

• sample activation from poor quality collect.
• in vivo activation e.g. post surgery, trauma, in pregnancy, chronic DIC.

See

Echis Ratio

INR

Contact Information

For further information contact the Haematology laboratory (Ext 22067) or:

Dr Nicola Eaddy	Ext 22005
Dr Peter Bradbeer	Ext 22062
Dr Anna Ruskova	Ext 22137
Dr Nikhil Rabade	Ext 22071

Last updated at 13:09:28 11/09/2024