Activated Protein C Resistance

What is the Activated Protein C Resistance Test?

The Activated Protein C (APC) Resistance test evaluates how effectively activated protein C controls blood clot formation. Activated protein C is a natural anticoagulant that slows clotting by inactivating clotting factors V and VIII. When resistance is present, clotting activity increases, raising the risk of abnormal blood clots.

The most common cause of APC resistance is the Factor V Leiden mutation, a genetic change that makes factor V less responsive to regulation by activated protein C. This results in a hypercoagulable state, meaning the blood has a higher tendency to clot than normal.

This test is widely used as a functional screening tool for inherited thrombophilia, particularly when there is a personal or family history of unexplained clotting events.

Why do I need a test for Activated Protein C Resistance?

You may need this test if you have experienced unexplained blood clots, recurrent miscarriages, or if there is a family history of thrombosis. APC resistance is one of the most common inherited risk factors for venous thromboembolism and can significantly increase clotting risk, especially when combined with other factors.

Testing is also recommended before prescribing oestrogen-containing medications, during fertility investigations, or when clotting occurs at a young age or in unusual locations. Identifying APC resistance helps guide prevention strategies and long-term management.

Symptoms and scenarios where testing is recommended:

• Deep vein thrombosis (DVT)
• Pulmonary embolism (PE)
• Blood clots at a young age
• Recurrent pregnancy loss
• Family history of thrombosis
• Clotting after surgery or immobilisation
• Thrombosis without obvious trigger
• Pre-treatment assessment before hormone therapy

Benefits of the Activated Protein C Resistance Test

• Identifies inherited clotting risk early
  Detects functional resistance associated with Factor V Leiden mutation.
• Helps explain unexplained thrombosis
  Provides insight into clotting events without clear external cause.
• Guides personalised prevention strategies
  Supports decisions around anticoagulation, lifestyle and medication use.
• Useful in fertility and pregnancy assessment
  Identifies clotting risks linked to miscarriage and pregnancy complications.
• Supports safe prescribing of hormone therapy
  Helps assess clotting risk before oestrogen-based treatments.
• Reduces risk of recurrent clotting events
  Enables proactive risk management once identified.
• Complements genetic testing
  Functional testing can be followed by confirmatory genetic analysis.
• Simple and clinically powerful test
  Requires only a standard blood sample.

Step-by-Step: How Testing Works

Choose your preferred testing method

You can attend one of our UK partner clinics or arrange a home or hotel visit with a mobile phlebotomist.

Option 1 – In-Clinic Blood Draw

1. Select your nearest UK clinic and book an appointment.
2. A clinician or phlebotomist collects a venous blood sample.
3. The sample is analysed for activated protein C response.
4. Results are delivered securely online.

Option 2 – Home or Hotel Phlebotomy (+£60)

1. Book a UK-wide home or hotel visit at a convenient time.
2. A trained phlebotomist collects your blood sample on-site.
3. The sample is packaged and transported to the laboratory.
4. Results are uploaded digitally without the need to travel.

Access your report

You can download and share your results with your GP, haematologist or fertility specialist if required.

Your Results Explained

Low / Reduced Response (Resistance Present)

Reduced response indicates activated protein C resistance.
This suggests an increased risk of venous thrombosis, commonly associated with Factor V Leiden mutation.
Further genetic testing may be recommended to confirm the underlying cause.

Normal Response

A normal result means activated protein C is functioning correctly.
This indicates no evidence of APC resistance at the time of testing.

High Sensitivity / Enhanced Response

Enhanced response is uncommon and generally not clinically significant.
Results should always be interpreted alongside clinical history and other clotting tests.