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Vitamin K Anticoagulant Activity Pattern in Plasma (Prothrombin Time/INR Interpretation)

Published: August 9, 2026Updated: August 17, 2026

This test evaluates how your blood clots by measuring the time it takes for plasma to clot under vitamin K influence. It helps assess liver function, vitamin K status, and potential bleeding disorders.

Quick summary

["This test helps diagnose or monitor conditions affecting blood clotting and liver health."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
33478-9
Short code
VLCFA Pattern SerPl-Imp
Synonyms
VLCFA Pattern SerPl-Imp
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
0
Ref high
17
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why This Test Is Done

Your doctor may order this test if you have symptoms like easy bruising, excessive bleeding, or unexplained clots. It’s also used to check liver function, monitor vitamin K levels, or evaluate conditions like liver disease, vitamin K deficiency, or blood clotting disorders.

How the Test Works

Blood is drawn and mixed with a reagent to measure the time it takes for clotting to occur. This time is compared to a standard to determine your anticoagulant activity pattern.

What to Expect Before the Test

No special preparation is needed, but inform your doctor about medications (especially blood thinners) or recent illnesses that might affect results.

What the Results Mean

Results show whether your blood clotting is slowed (indicating possible vitamin K deficiency, liver issues, or anticoagulant use) or normal. Interpretation often involves comparing your prothrombin time (PT) or international normalized ratio (INR) to reference ranges.

Reference range

NCBI: NSE 0-17 ng/mLN/A

Specimen: serum

No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

VKAP (PT/INR Pattern)

Frequently asked questions

What does a prolonged PT/INR indicate?
A prolonged PT/INR may suggest vitamin K deficiency, liver disease, or medications that interfere with clotting (e.g., blood thinners like warfarin). It can also indicate conditions like cirrhosis or bleeding disorders.
What does a normal PT/INR indicate?
A normal PT/INR suggests healthy blood clotting function, but further evaluation may still be needed if symptoms persist (e.g., unexplained bruising).
How often should this test be repeated?
Your doctor will determine frequency based on your condition. For example, patients on blood thinners may need regular monitoring, while others may only need it once if symptoms resolve.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 17, 2026. · Read our editorial policy