What is the NK Assay / Cytotoxicity Panel?

The NK Assay / Cytotoxicity Panel is a functional immune test that evaluates the activity of natural killer (NK) cells, a critical part of the innate immune system. Rather than just counting NK cells, this test measures how effectively they can identify and destroy virus-infected or abnormal cells.

NK cells play a key role in early antiviral defence, cancer surveillance, and immune regulation. Reduced cytotoxic activity may be present even when NK cell numbers are normal, making functional testing essential in selected clinical contexts.

Why do I need an NK Cytotoxicity test?

Standard immune tests often measure cell numbers but do not assess how well those cells function. The NK assay provides deeper immune insight.

You may benefit from this test if you:

• Have recurrent or persistent viral infections

• Experience chronic fatigue or immune dysfunction

• Have unexplained immune suppression

• Are being investigated for immune dysregulation

• Have suspected post-viral syndromes

• Are undergoing immune system assessment

• Require advanced immune profiling

The test helps determine whether immune defence is functioning effectively at a cellular level.

Benefits of the test

1. Measures immune function, not just cell count
   Assesses real-world NK cell activity.

2. Supports investigation of recurrent infections
   NK cells are critical in viral defence.

3. Provides insight into immune surveillance
   Important in tumour and abnormal cell detection.

4. Useful in complex immune presentations
   Adds depth beyond routine immune tests.

5. Specialised immune assessment
   Not captured by standard blood panels.

6. Supports personalised immune evaluation
   Helps guide further immune investigation.

7. Widely used in immunology research and clinics
   Accepted functional immune assay.

8. Single blood-based test
   Requires one carefully handled sample.

Step-by-step: How we offer testing

Clinic-based testing (UK-wide)

• Choose your nearest UK clinic

• Attend your appointment

• Blood sample taken and processed promptly

• Sample sent to a specialist laboratory

• Results issued once analysis is complete

Home or hotel visit (+£60, UK-wide)

• Mobile phlebotomist attends your location

• Blood sample taken with strict handling requirements

• Sample transported rapidly to the laboratory

Due to the functional nature of the test, strict sample timing and handling are essential.

Your results explained

Low NK cytotoxic activity

• Reduced ability of NK cells to destroy target cells

• May be associated with viral susceptibility or immune suppression

• Requires interpretation with symptoms and immune markers

Normal NK cytotoxic activity

• NK cell function within expected range

• Suggests intact innate immune defence

High NK cytotoxic activity

• Increased NK cell activity

• May be seen in immune activation or inflammation

• Requires clinical correlation

Reference ranges vary by laboratory and assay method.