Consultant-Led Clinical Immunology

Clinical Immunology Assessment in London

Specialist assessment for suspected common variable immunodeficiency (CVID), antibody deficiency, recurrent infections, immune dysregulation and complement disorders. Our reviews are designed to look carefully at humoral immunity, cellular immunity, complement pathways and functional antibody responses to vaccines.

At the London Allergy & Immunology Centre, patients are assessed by experienced clinicians using a structured, evidence-based approach informed by current UK and international immunology guidance.

What this page covers: CVID assessment, recurrent infection work-up, IgG subclasses, lymphocyte subsets, complement screening, vaccine antibody responses, MenB and MenACWY review, and current UK vaccine schedule changes relevant to immunodeficiency testing.

What is a clinical immunology assessment?

A clinical immunology assessment is a specialist review of how the immune system is functioning. It is often requested for patients with recurrent infections, unexplained low immunoglobulins, poor vaccine responses, bronchiectasis, autoimmune complications, or a history that raises concern for an inborn error of immunity.

One of the most important adult antibody deficiencies is common variable immunodeficiency. CVID is not diagnosed from one blood result alone. Diagnosis usually requires a careful clinical history, repeat immunoglobulin testing, exclusion of secondary causes of hypogammaglobulinaemia, and assessment of how well the patient makes protective antibodies after vaccination or natural exposure.

Because immunodeficiency can overlap with allergy, autoimmune disease, inflammation and chronic infection, the most useful assessments are those that combine laboratory data with proper specialist interpretation rather than relying on isolated test numbers alone.

Four main parts of the assessment

1. Humoral immunity
Measures antibodies and B-cell related function, including IgG, IgA, IgM, IgE and IgG subclasses 1–4, together with specific antibody responses to vaccines and common pathogens.

2. Cellular immunity
Looks at lymphocyte subsets by flow cytometry, including CD3, CD4, CD8, CD19, CD20 and CD16/CD56, to assess T cells, B cells and natural killer cells.

3. Complement pathways
Screens for abnormalities in innate immune defence, typically with C3, C4, CH50 and, where indicated, mannose-binding lectin (MBL) and further complement pathway testing.

4. Functional antibody responses
Assesses whether the immune system makes protective antibodies after exposure to vaccines such as MenB, MenACWY, pneumococcus, tetanus, diphtheria and Hib.

Who may benefit from this assessment?

This type of review may be appropriate for people with:
• recurrent chest, sinus or ear infections
• bronchiectasis or chronic productive cough
• repeated antibiotic courses or hospital-treated infections
• unexpectedly low IgG, IgA or IgM
• poor recovery after routine childhood or adult vaccines
• family history of immunodeficiency or recurrent severe infection

We also consider immunology input where there is:
• autoimmune cytopenia, inflammatory bowel problems or immune dysregulation
• unexplained lymphadenopathy or splenomegaly
• suspected complement deficiency or meningococcal risk
• concern about response to immunisation before or during immunosuppressive treatment
• a complex picture overlapping allergy, infection and immune dysfunction

What tests are commonly included?

Area Typical tests Why it matters
Baseline blood work Full blood count, white cell differential, inflammatory markers where relevant Provides context for lymphopenia, neutropenia, inflammation and infection pattern
Immunoglobulins IgG, IgA, IgM, IgE, sometimes repeat confirmation testing Core first-line testing in suspected antibody deficiency and CVID
IgG subclasses IgG1, IgG2, IgG3, IgG4 Can help clarify recurrent infection patterns, especially where total IgG is borderline or normal
Lymphocyte subsets CD3, CD4, CD8, CD19, CD20, CD16/CD56 Assesses T-cell, B-cell and NK-cell numbers and helps identify combined immune defects
Complement screen C3, C4, CH50, with MBL or other pathway testing if indicated Useful in recurrent invasive bacterial infection, suspected complement deficiency or immune complex disease
Functional antibodies Pneumococcal serotypes, tetanus, diphtheria, Hib, MenB, MenACWY and selected infection serology Shows whether the immune system is making protective antibodies rather than only measuring total immunoglobulin levels
Exact testing is individualised. Not every patient needs every investigation, and reference ranges vary by laboratory and age.

IMPORTANT UK VACCINE UPDATE

Why recent vaccine schedule changes matter in immunology testing

When interpreting antibody results, it is essential to know which vaccine was given, when it was given, and whether the product was a conjugate vaccine or a polysaccharide vaccine. That is particularly important in suspected CVID and related antibody deficiencies.

Menitorix: the routine Hib/MenC dose at 12 months was removed from the UK childhood schedule from July 2025, and the programme now includes a Hib-containing hexavalent booster at 18 months. This means older and younger children may have received different products and schedules, which must be taken into account when reviewing Hib or meningococcal immunity.

Pneumococcal vaccination: in higher-risk groups, interpretation now increasingly involves PCV20 as well as older polysaccharide-based assessment strategies. For some immunology patients, previous vaccination with PPV23, PCV13 or PCV20 can materially affect how results should be understood.

In practice, this means that vaccine history is part of the diagnostic work-up, not just an administrative detail.

Humoral immunity assessment

Humoral immunity refers to the antibody-producing part of the immune system. In suspected CVID, this is usually the starting point. The assessment commonly includes IgG, IgA, IgM, IgE and IgG subclasses.

Low total IgG alone does not automatically mean CVID. We also consider whether low results are persistent, whether there are associated reductions in IgA or IgM, whether the pattern fits the clinical history, and whether there may be secondary causes such as medication effects, protein loss, nephrotic syndrome, malignancy or previous B-cell depleting treatment.

Typical humoral review includes:
• total immunoglobulins: IgG, IgA, IgM, IgE
• IgG subclasses: IgG1, IgG2, IgG3, IgG4
• baseline protective antibodies where relevant
• repeat confirmation testing where the diagnosis remains uncertain

Cellular immunity and lymphocyte subsets

Flow cytometry can be used to count the main lymphocyte populations. This helps separate a predominantly antibody problem from a broader immunodeficiency and may guide further investigation.

Marker Cell type Why it is checked
CD3 Total T cells Useful first-line measure of cellular immunity
CD4 Helper T cells Relevant for immune coordination and antibody support
CD8 Cytotoxic T cells Helps assess antiviral and cellular immune balance
CD19 / CD20 B cells Important in antibody deficiency and after B-cell directed therapy
CD16 / CD56 Natural killer cells Part of innate lymphocyte assessment when broader immune dysfunction is suspected

Advanced B-cell phenotyping may be considered in selected cases, particularly where CVID remains likely after first-line testing.

Complement assessment

Complement proteins are part of innate immune defence and are especially important in protection against certain bacterial infections, including meningococcal disease. Defects may be inherited or acquired, and some abnormalities reflect immune consumption rather than primary deficiency.

C3 and C4
Useful screening markers for complement deficiency, activation and immune-complex related disease.

CH50
A functional screening test for the classical complement pathway and terminal complement activity.

MBL and extended tests
Considered when the history suggests lectin pathway issues, recurrent invasive infection or a more complex complement disorder.

Specific antibody responses to vaccines and common infections

This is often the part of the work-up that turns a suspicion into a clearer diagnosis. Some patients have immunoglobulin levels that are only mildly abnormal, yet their immune system still fails to produce reliable protective antibodies.

Depending on age, vaccine history and clinical need, we may review antibody responses to the following:

Pneumococcus
Important in suspected antibody deficiency, especially in recurrent chest and sinus infection.

Tetanus and diphtheria
Useful protein-antigen responses when assessing functional humoral immunity.

Hib
Interpreted in the context of changing UK childhood vaccine schedules.

MenB
Particularly relevant in patients with complement-related risk or a history suggesting meningococcal vulnerability.

MenACWY
Reviewed when meningococcal protection is clinically important or vaccination history needs clarification.

Selected infection serology
May include common infection markers where clinically helpful, though interpretation depends on the full picture.

Diagnostic pathway for suspected CVID and related immune deficiency

Step 1 – Clinical history and pattern recognition
We start with the infection history, severity, frequency, autoimmune features, inflammatory symptoms, family history, prior vaccine history and any medications that could affect immunity.

Step 2 – First-line laboratory testing
This usually includes immunoglobulins, IgG subclasses, lymphocyte subsets and complement screening, with baseline antibody titres where appropriate.

Step 3 – Exclude secondary causes
Before confirming a primary antibody deficiency, it is important to consider medication-related causes, protein loss, malignancy, renal loss and other acquired explanations.

Step 4 – Functional antibody assessment
If needed, antibody responses to relevant vaccines are reviewed before and after vaccination, depending on the clinical question and previous immunisation history.

Step 5 – Specialist interpretation and management plan
Results are interpreted in context. Management may include observation, further testing, vaccination planning, antibiotic strategies, or discussion of immunoglobulin replacement therapy where appropriate.

What to expect at your appointment

Your consultation will usually involve a detailed review of your infection history, previous blood tests, scans, treatments, vaccination record and relevant family history.

Some patients already have results that suggest antibody deficiency. Others need a staged investigation plan. Not all testing is done on the same day, because interpretation often depends on what has already been found and whether repeat testing is needed.

Where clinically appropriate, follow-up may include advice on further vaccination assessment, microbiology review, imaging, organ-specific screening or referral for longer-term immunology management.

Frequently asked questions

Can CVID be diagnosed from one blood test?
Usually not. A proper diagnosis normally requires repeat testing, clinical history, exclusion of secondary causes and assessment of antibody function.

Why are vaccine responses important?
They show whether the immune system can make protective antibodies. This is often more clinically useful than looking at total immunoglobulin levels alone.

Will everyone need complement testing?
No. Complement investigations are usually guided by the clinical history, particularly recurrent invasive bacterial infection, meningococcal disease, or features suggesting complement consumption.

Do I need a GP referral?
Private patients can usually self-refer. If you already have relevant blood tests, letters or scans, it is helpful to send them in advance.

Selected references and guidance

1. UK Health Security Agency. Changes to the routine childhood vaccination schedule from 1 July 2025 and 1 January 2026.
2. UK Health Security Agency. Haemophilus influenzae type b (Hib) chapter, Green Book update, 2026.
3. UK Health Security Agency and NHS England. Change of vaccine for the routine adult pneumococcal vaccination programme and individuals at increased clinical risk, 2025.
4. UK Health Security Agency. Pneumococcal vaccination for older adults and individuals in a clinical risk group: information for healthcare practitioners, updated 2026.
5. UK Health Security Agency. Meningococcal chapter, Green Book, 2025.
6. Recent reviews on CVID, diagnostic testing for primary immunodeficiency, and flow cytometry in inborn errors of immunity, 2024–2025.

Information on this page is for education and service overview only and does not replace individual medical advice.

London Allergy & Immunology Centre

Book a clinical immunology consultation

Consultant-led assessment for suspected CVID, recurrent infections, low immunoglobulins, complement disorders and complex immune problems.

Book Online
Call 020 3143 3449

Dr Robert Boyle - MB ChB, MRCPCH, PhD