What is the Lymphocyte Subsets Test?

The Lymphocyte Subsets test is a specialised blood test that measures different types of lymphocytes, a group of white blood cells essential for immune defence. Using flow cytometry, the test identifies and quantifies specific immune cell populations based on surface markers.

The main lymphocyte subsets assessed include T lymphocytes (CD3), helper T cells (CD4), cytotoxic T cells (CD8), B lymphocytes (CD19) and natural killer (NK) cells (CD16/CD56). Evaluating these subsets provides a detailed picture of immune competence and regulation.

This test is widely used in immunology, infectious disease and haematology to investigate immune deficiency, immune activation and treatment effects.

Why do I need a test for Lymphocyte Subsets?

You may need this test if there is concern about immune system dysfunction, recurrent infections or unexplained inflammatory or autoimmune conditions. Changes in lymphocyte populations can indicate immune suppression, immune activation or imbalance.

The test is also essential for monitoring conditions that directly affect immune cells and for assessing response to treatments that influence immune function.

Symptoms and scenarios where testing is recommended:

• Recurrent or unusual infections
• Suspected immune deficiency
• Chronic viral infections
• Monitoring immunosuppressive therapy
• Autoimmune or inflammatory disorders
• Unexplained lymphopenia or lymphocytosis
• Post-transplant immune monitoring
• HIV or other immune-related assessments

Benefits of the Lymphocyte Subsets Test

• Detailed immune system profiling
  Goes beyond a standard white cell count.
• Identifies immune deficiencies
  Detects reduced or abnormal lymphocyte populations.
• Assesses immune activation or suppression
  Helps evaluate immune balance.
• Supports infection risk assessment
  Identifies vulnerability to opportunistic infections.
• Monitors immune-modulating treatments
  Useful during chemotherapy or immunosuppression.
• Guides further immunological testing
  Helps direct targeted investigations.
• Clinically established diagnostic tool
  Widely used in specialist care.
• Supports long-term immune monitoring
  Tracks immune changes over time.

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 levels of specific lymphocyte subsets may indicate immune deficiency, bone marrow suppression or effects of medication.
Reduced CD4 cells, for example, can increase susceptibility to infections.

Typical UK reference ranges vary by subset and laboratory.

Normal Levels

Normal lymphocyte subset distribution suggests balanced and functional immune activity.
This supports effective immune defence and regulation.

High Levels

Elevated lymphocyte subsets may reflect immune activation, chronic infection or inflammatory conditions.
Further investigation may be required depending on clinical context.