What is the Complement C2 test?

The Complement C2 test measures the level of Complement Component 2, a protein involved in the classical and lectin pathways of the complement system. The complement system is part of the innate immune response and plays a vital role in fighting infections and clearing immune complexes.

Complement C2 works alongside other complement proteins to help identify, mark, and eliminate pathogens. Adequate levels are essential for effective immune defence and regulation of inflammation.

This test is mainly used in immunology and haematology to investigate suspected complement deficiencies or immune dysfunction.

Why do I need a Complement C2 test?

Complement C2 deficiency is rare but can predispose individuals to recurrent infections and autoimmune conditions. Testing is usually performed when immune system abnormalities are suspected.

You may need a Complement C2 test if you:

• Have recurrent bacterial infections
• Experience severe or unusual infections
• Have suspected immune deficiency
• Have autoimmune or inflammatory conditions
• Have unexplained low complement levels
• Are undergoing immune system evaluation
• Have family history of complement deficiencies

Symptoms associated with complement deficiency may include:

• Frequent respiratory infections
• Skin infections
• Delayed recovery from infections
• Increased susceptibility to certain bacteria

Benefits of the Complement C2 test

• Assesses immune complement function
  Evaluates a key component of innate immunity.
• Supports diagnosis of rare immune deficiencies
  Helps identify C2 deficiency.
• Useful in recurrent infection assessment
  Investigates underlying immune causes.
• Supports autoimmune disease evaluation
  Complement imbalance may contribute to autoimmunity.
• Clinically recognised immune marker
  Used in specialist immunology testing.
• Simple blood test
  Requires only a single blood sample.
• Supports further immune investigations
  Guides additional complement testing.
• Improves diagnostic clarity
  Helps explain unexplained immune symptoms.

Step by step – how the test works

You can access Complement C2 testing UK-wide through two options:

1. Clinic appointment
   Choose your nearest UK clinic, where a healthcare professional will take your blood sample.
2. At-home or hotel visit (£60 extra)
   A qualified phlebotomist comes to your home or hotel, so you don’t need to travel.

Your sample is analysed in an accredited UK laboratory, and results are delivered securely.

Your results explained

Low Complement C2 levels

May indicate congenital or acquired C2 deficiency and can be associated with increased infection risk or autoimmune disease.

Typical UK interpretation:

• Below laboratory reference range

Normal Complement C2 levels

Suggest intact complement pathway function.

Typical UK interpretation:

• Within laboratory reference range

High Complement C2 levels

May be seen in inflammatory states or acute immune activation.

Typical UK interpretation:

• Above laboratory reference range

Reference ranges vary between laboratories and must be interpreted in clinical context.