Prothrombin Time
Private Prothrombin Time blood test in London for £58, measuring one coagulation marker with results expected in around 1–2 days.
Turnaround time
1-2 business days
Biomarkers count
1
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Overview of the Prothrombin Time Test
The Prothrombin Time blood test measures how long it takes blood to form a clot through the extrinsic and common coagulation pathways.
The test contains 1 biomarker: Prothrombin Time.
Normal blood clotting depends on a carefully controlled sequence of coagulation factors. Prothrombin Time, commonly abbreviated to PT, assesses the activity of several of these factors, including factors I, II, V, VII and X.
Many of these clotting proteins are produced by the liver, while several depend on Vitamin K for normal function.
A prolonged Prothrombin Time can therefore occur for several reasons, including anticoagulant treatment, significant Vitamin K deficiency, reduced production of clotting factors by the liver and selected inherited or acquired coagulation disorders.
Prothrombin Time is also closely related to the International Normalised Ratio, or INR.
The INR is a standardised mathematical expression of PT and is especially important when monitoring people taking Warfarin or another Vitamin K antagonist.
The standalone Prothrombin Time result should not be interpreted as a general measure of whether someone is likely to develop an unwanted blood clot.
A prolonged PT primarily indicates slower coagulation through the pathways measured by the test and may increase bleeding risk depending on the degree of prolongation and the underlying cause.
Other parts of the coagulation system require separate testing. APTT assesses different clotting pathways, while Fibrinogen, platelet measurements and specialist factor assays answer different questions.
The result is therefore most informative when interpreted with medication history, liver function, bleeding symptoms and any complementary coagulation tests.
What Does the Prothrombin Time Test Check?
The test assesses the speed of clot formation through the extrinsic and common coagulation pathways and can provide information about clotting-factor function. This test measures 1 biomarker.
Prothrombin Time
Measures the time required for plasma to clot through the extrinsic and common coagulation pathways, providing information about several clotting factors and the effect of Vitamin K antagonist therapy.
Who May Benefit From the Prothrombin Time Test?
Prothrombin Time testing may be useful when abnormal bleeding, anticoagulant treatment, liver disease or a previous coagulation abnormality needs further assessment.
People taking Warfarin - PT forms the basis of INR monitoring used to assess the anticoagulant effect of Warfarin.
People with unexplained prolonged bleeding - A prolonged PT can provide evidence of impaired activity within the measured clotting pathways.
People with unexplained bruising alongside other bleeding symptoms - Coagulation testing may form part of a broader investigation.
People with liver disease - The liver produces many clotting factors, so significant liver dysfunction can affect PT.
People with suspected Vitamin K deficiency - Several factors measured by PT depend on Vitamin K.
People with a previous prolonged PT or raised INR - Repeat testing can establish whether the abnormality remains present.
People undergoing selected pre-operative investigations - PT may be requested where medical history or the planned procedure indicates a need for coagulation assessment.
People being investigated for a clotting-factor deficiency - PT can provide initial screening information before individual factor assays are considered.
How to Prepare
Do not stop Warfarin or another anticoagulant independently in order to obtain a different test result.
Coagulation tests require an accurately filled citrate specimen, so professional collection and appropriate sample handling are important.
Symptoms and Reasons to Consider the Prothrombin Time Test
Abnormal PT itself does not produce symptoms. Clinical features arise from the underlying coagulation problem and are particularly relevant when bleeding occurs unusually easily or lasts longer than expected.
Prolonged bleeding after a cut or injury - Reduced coagulation-factor activity can delay stable clot formation.
Unexpectedly heavy bleeding after surgery or dental treatment - A clotting abnormality may form part of the investigation.
Frequent significant nosebleeds - Recurrent bleeding can justify broader haemostatic assessment.
Unexplained bruising with other bleeding features - PT can contribute to investigation, although platelet disorders and other causes must also be considered.
Heavy menstrual bleeding with suspected coagulation problems - A broader bleeding-disorder assessment may be appropriate.
Known liver disease with new bleeding symptoms - Reduced hepatic synthesis of clotting factors can prolong PT.
Unexpected bleeding while taking Warfarin - Anticoagulant effect may need urgent clinical review.
A previously abnormal coagulation result - Repeat testing can help determine whether the change persists.
A normal Prothrombin Time does not exclude every bleeding disorder. Platelet-function abnormalities, Von Willebrand disease and some clotting-factor deficiencies may occur with a normal PT.
Severe or uncontrolled bleeding, vomiting blood, black stools, significant head injury while anticoagulated or other major haemorrhage requires urgent medical assessment.
How to Book Your Prothrombin Time Test
The Prothrombin Time test can be booked privately through London Blood Tests for coagulation assessment or appropriate anticoagulant monitoring.
Choose the Prothrombin Time
Select the individual Prothrombin Time blood test online.
Select your sample collection option
Choose an appropriate in-clinic appointment or professional home or hotel phlebotomy service.
Attend your appointment
A trained healthcare professional collects the required citrate blood sample using the correct fill volume.
Laboratory analysis
Your specimen is analysed to measure Prothrombin Time through the relevant coagulation pathway.
Receive your results securely
Your authorised result is delivered securely and can be reviewed with the clinician responsible for your coagulation or anticoagulant care.
When Will I Receive My Results?
The current expected turnaround for the Prothrombin Time test is approximately 1–2 days after the sample reaches the laboratory.
Prothrombin Time is a routinely performed coagulation investigation, but accurate reporting depends on receiving a suitable citrate specimen.
The laboratory completes coagulation analysis, quality-control procedures and result authorisation before release.
Turnaround begins from laboratory receipt rather than necessarily from the exact time at which the blood sample is collected.
If the specimen is underfilled, clotted or otherwise unsuitable, repeat collection may be required and can delay reporting.
Urgent bleeding or suspected excessive anticoagulation requires clinical assessment rather than waiting for a routine private result.
Understanding Your Results
A Prothrombin Time within the laboratory reference interval indicates that clot formation through the measured pathways occurred within the expected timeframe.
A prolonged PT means clotting took longer than expected.
Potential causes include Warfarin treatment, significant Vitamin K deficiency, liver dysfunction and deficiencies or inhibitors affecting clotting factors measured by the assay.
When PT is used for Warfarin monitoring, interpretation is generally based on the INR, which standardises the result between laboratories and reagents.
Therapeutic INR targets vary according to why Warfarin has been prescribed.
A shortened PT is generally less clinically informative than a prolonged result and should not be interpreted as proof of an increased tendency to develop thrombosis.
Abnormal results should be considered with medication, bleeding history, liver function and complementary coagulation tests.
Why Book With London Blood Tests?
London Blood Tests provides private access to routine coagulation assessment with professional sample collection and secure laboratory reporting.
Targeted coagulation testing - Measures one of the principal laboratory pathways involved in blood clotting.
Relevant to Warfarin monitoring - PT provides the laboratory basis for INR assessment.
Useful in bleeding investigations - Can identify delayed clot formation within the measured pathways.
Relevant to liver health - Many factors affecting PT are produced by the liver.
Professional citrate sample collection - Correct specimen filling and handling are important for reliable coagulation results.
Private blood testing in London - Clinic and appropriate mobile collection options are available.
Fast results - Current turnaround is approximately 1–2 days after laboratory receipt.
Clear pricing - The Prothrombin Time test costs £58.
Private Prothrombin Time Blood Test in London
London Blood Tests provides private Prothrombin Time testing in London for people requiring assessment of blood-clotting pathways, Warfarin-related monitoring or investigation of an abnormal coagulation result.
The test costs £58 and measures 1 biomarker: Prothrombin Time.
Results are expected approximately 1–2 days after laboratory receipt.
The result should be interpreted with medication, bleeding history and other coagulation investigations where appropriate.