What is the IgG Subclasses test?

The IgG Subclasses test measures the levels of the four subclasses of Immunoglobulin G (IgG1, IgG2, IgG3 and IgG4) in the blood. IgG is the most abundant antibody in the immune system and plays a crucial role in protecting against bacterial and viral infections.

Each IgG subclass has a distinct role in immune defence. Some are more important for responding to bacteria, others for viruses, and some for immune regulation. A person may have a normal total IgG level but still have a deficiency in one or more subclasses.

This test is used in immunology and infectious disease assessment, particularly when recurrent infections occur despite normal routine blood results.

Why do I need an IgG Subclasses test?

Selective IgG subclass deficiencies can impair the body’s ability to fight infections, especially respiratory and sinus infections, even when total IgG appears normal.

You may need an IgG Subclasses test if you:

• Have recurrent chest, sinus or ear infections
• Have frequent infections requiring antibiotics
• Have poor response to vaccines
• Have suspected immune deficiency
• Have chronic respiratory symptoms
• Have unexplained fatigue linked to infections
• Are being assessed by an immunologist

Symptoms commonly associated with IgG subclass deficiency include:

• Recurrent respiratory infections
• Chronic sinusitis
• Ear infections
• Bronchitis or pneumonia
• Prolonged recovery from infections

Benefits of the IgG Subclasses test

• Detects selective immune deficiencies
  Identifies subclass-specific antibody issues.
• Explains recurrent infections
  Even when standard tests are normal.
• Supports immunology referrals
  Provides specialist-level immune insight.
• Guides vaccination strategy
  Helps assess vaccine response capability.
• Clinically recognised immune test
  Used in NHS and specialist immunology clinics.
• Useful in children and adults
  Applied across age groups.
• Supports long-term immune monitoring
  Helps track immune function over time.
• Simple blood test
  Requires only a single blood sample.

Step by step – how the test works

You can access IgG Subclasses testing UK-wide through two options:

1. Clinic appointment
   Attend 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 IgG subclass levels

May indicate selective antibody deficiency and increased susceptibility to infections.

Typical UK interpretation:

• One or more IgG subclasses below reference range

Normal IgG subclass levels

Suggest intact antibody-mediated immune defence.

Typical UK interpretation:

• All subclasses within reference range

High IgG subclass levels

May be seen in chronic inflammation, immune activation or certain autoimmune conditions.

Typical UK interpretation:

• One or more subclasses above reference range

Results must always be interpreted in clinical context.