Blood Sciences Test

Prothrombin Time (PT)


Sodium citrate tube (blue top)

For Neonates we can prepare half volume paediatric tubes, which will require 0.65 mL blood (filled to the black line). Please contact the Coagulation Section on extension 2916 before 1600 weekdays if you require these tubes.

Special Instructions

The tube must be filled correctly (filled to line on tube).

Samples should be received in the laboratory on the same day.

Factors affecting results

Haemolysed or clotted samples cannot be tested. To avoid haemolysis and clotted samples mix tube gently by inversion, do not shake.

Patients on anticoagulants will have abnormal results

Reference Ranges



In house

The prothrombin time is performed as part of the Coagulation Screen (Diagnostic).

STAT availability


Turnaround times

1 hr – STAT samples

4 hr – routine samples

Clinical Advice

Clinical advice is available from the Haematology Medical team (contact RD&E switchboard on 01392 411611)

Specimen Labelling Procedure