What is the Streptococcus Pneumoniae IgG 23 Serotypes Test?

The Streptococcus Pneumoniae IgG 23 Serotypes test measures IgG antibody levels against 23 different pneumococcal serotypes most commonly associated with invasive disease. These antibodies play a key role in protecting against bacterial infections affecting the lungs, bloodstream, and central nervous system.

The test is often used to evaluate immune competence, particularly the body’s ability to produce protective antibodies following natural exposure or vaccination (such as the 23-valent pneumococcal polysaccharide vaccine). It provides a detailed serotype-by-serotype assessment rather than a single total antibody value.

This test is widely used in immunology to investigate recurrent infections, suspected antibody deficiency, or inadequate vaccine response.

Why do I need a Streptococcus Pneumoniae IgG test?

Streptococcus pneumoniae is a leading cause of pneumonia, sinusitis, otitis media, sepsis, and meningitis. Some individuals are more susceptible to these infections due to impaired antibody production, even if routine blood tests appear normal.

You may benefit from this test if you experience:

• Recurrent chest infections or pneumonia
• Frequent sinus or ear infections
• Poor response to previous vaccinations
• Suspected immune deficiency
• Chronic lung disease with repeated infections
• Infections requiring frequent antibiotics
• Post-splenectomy or functional asplenia
• Monitoring immune response after pneumococcal vaccination

This test helps determine whether your immune system can mount an adequate antibody response and whether further immunological assessment may be required.

Benefits of the test

1. Comprehensive immune assessment
   Measures antibodies to 23 clinically relevant pneumococcal serotypes.
2. Evaluates vaccine response
   Assesses whether pneumococcal vaccination has generated protective immunity.
3. Identifies functional antibody deficiency
   Detects impaired immune responses even when total IgG is normal.
4. Supports investigation of recurrent infections
   Particularly useful for repeated respiratory or ENT infections.
5. Guides further immunology testing
   Helps determine if advanced immune investigations are needed.
6. Useful in adults and children
   Applicable across age groups with recurrent infections.
7. Objective, measurable results
   Provides numeric antibody levels per serotype.
8. Improves long-term infection risk assessment
   Helps stratify susceptibility to pneumococcal disease.

Step-by-step: How we offer testing

Clinic-based testing (UK-wide)

• Choose your nearest UK clinic
• Attend your appointment
• A clinician draws a blood sample
• Sample is sent to the laboratory
• Results are issued once analysis is complete

Home or hotel visit (+£60, UK-wide)

• Book a mobile phlebotomist
• Blood sample taken at your home or hotel
• No need to travel to a clinic
• Sample securely transported to the laboratory

Your results explained

Low antibody levels (insufficient protection)

• Antibody levels below protective thresholds in multiple serotypes
• UK standard: Protective level generally ≥1.3 µg/mL per serotype
• Suggests reduced immune response or impaired vaccine response

Normal antibody levels (adequate protection)

• Protective antibody levels present across most serotypes
• UK standard: ≥1.3 µg/mL in the majority of tested serotypes
• Indicates functional antibody-mediated immunity

High antibody levels (strong immune response)

• Elevated IgG levels across many or all serotypes
• UK standard: Values above protective thresholds
• Often reflects recent vaccination or strong immune memory