What is the CD56 Test?

The CD56 test measures the number and proportion of CD56-positive natural killer (NK) cells, a critical component of the innate immune system. CD56 is a surface marker used to identify NK cells, which play a key role in early defence against viral infections and abnormal cells.

NK cells act without prior sensitisation and are essential for immune surveillance, particularly in recognising and eliminating virus-infected cells and tumour cells. Measuring CD56 helps assess the functional status of innate immunity.

This test is commonly performed as part of lymphocyte subset analysis or targeted immune assessment.

Why do I need a test for CD56?

You may need this test if there is concern about immune dysfunction, recurrent infections or abnormal immune responses. Altered NK cell levels can be seen in chronic infections, autoimmune disorders, immune deficiency and during immunosuppressive treatment.

Testing CD56-positive cells helps clinicians understand whether innate immune activity is reduced, normal or excessively activated.

Symptoms and scenarios where testing is recommended:

• Recurrent or severe viral infections
• Suspected immune deficiency
• Chronic fatigue or immune dysregulation
• Monitoring immunosuppressive therapy
• Autoimmune or inflammatory conditions
• Cancer or immune surveillance assessment
• Unexplained lymphocyte abnormalities
• Post-transplant immune monitoring

Benefits of the CD56 Test

• Assesses natural killer cell levels
  Direct measure of innate immune cells.
• Supports immune deficiency investigation
  Identifies reduced NK cell activity.
• Evaluates immune surveillance capacity
  Important in infection and cancer defence.
• Useful in chronic infection assessment
  NK cells are vital in viral control.
• Monitors immune-modulating treatments
  Tracks effects of immunosuppression.
• Complements lymphocyte subset testing
  Adds detail beyond total lymphocyte counts.
• Clinically established immunology marker
  Widely used in immune profiling.
• Supports long-term immune monitoring
  Useful in complex immune conditions.

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 using flow cytometry.
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 transported to the laboratory.
4. Results are uploaded digitally without the need to travel.

Your Results Explained

Low Levels

Low CD56-positive NK cell levels may indicate immune suppression, chronic infection or bone marrow suppression.
Reduced NK cells can increase susceptibility to viral infections.

UK reference ranges vary by laboratory and testing method.

Normal Levels

Normal CD56 levels suggest balanced innate immune activity.
This supports effective immune surveillance and viral defence.

High Levels

Elevated CD56-positive cells may reflect immune activation, chronic inflammation or recovery from infection.
Clinical correlation is required to determine significance.