Primary immunodeficiency diagnosis

What is primary immunodeficiency diagnosis?

Primary immunodeficiency (also called an inborn error of immunity) means a person is born with a part of their immune system that does not work properly. The immune system is the body's defence against infection, so the usual sign is infections that are too frequent, too severe, last too long, are in unusual places, or are caused by unusual germs. Some types also cause problems with the body attacking itself or with inflammation.

Diagnosis is the process a consultant immunologist uses to work out whether there really is an immune problem, what type it is, and how serious it is likely to be. It is usually a series of steps rather than a single test: a detailed history, an examination, and blood tests that are interpreted together and sometimes repeated.

The most common group affects antibodies (immunoglobulins) — proteins the body uses to fight infection. Tests measure the level of different antibodies and, importantly, how well your body responds to vaccines. Other tests look at immune cells, the complement system and how white cells called neutrophils work. Where a specific inherited condition is suspected, genetic testing may be arranged.

It is important to understand what this process can and cannot do. It can identify many treatable immune conditions and reassure people who do not have one. It cannot always give a quick answer, no single test rules everything in or out, and some people are left with an uncertain or unexplained result even after thorough testing.

Types, options & approaches

There may be different ways to do this. The right approach depends on the clinical question and your circumstances.

What different tests are looking for

No single test is enough on its own — the consultant interprets them together with your history.

Preparing for your test

• Make a timeline of your infections: how often, how severe, where in the body, which germs if known, and how each was treated.
• Note hospital admissions, courses of antibiotics, and any infections that needed intravenous (drip) treatment.
• Bring details of any family history of immune problems, recurrent serious infections, or early deaths from infection.
• List all your medicines, especially steroids or immune-suppressing drugs, which can affect both your immunity and the test results.
• Bring records of previous blood tests, vaccinations and any earlier specialist letters.
• Note other symptoms such as ongoing tiredness, weight loss, diarrhoea, swollen glands or problems with inflammation.
• Be ready for the answer to come in stages, as some tests are done weeks apart and a few need repeating.

What happens

The consultant immunologist takes a detailed history of your infections and general health, and examines you. They are looking for the pattern of infection, signs of complications such as lung damage, and clues to other causes.

You usually have an initial set of blood tests, which may include a full blood count and immunoglobulin (antibody) levels. To test how well your antibodies work, you may be given a vaccine — often a pneumococcal vaccine — and asked to return about four weeks later for a blood test to measure your response.

Depending on what is suspected, more specialised tests are arranged over time: immune cell counts by flow cytometry, complement or neutrophil function tests, or genetic testing. You leave with an explanation of what is being looked for, which tests have been requested, and a clear follow-up plan. Because the picture builds up over time, a firm diagnosis often does not come at the first visit.

Is this test right for me?

A good consultation should explore whether it's the right choice for you now — including reasons to wait or consider something else.

Before you decide

Use this as a shared-decision checklist. The aim is not just “can this be done?”, but whether it is right for you, now, with the risks and alternatives clearly understood.

The main challenge is that primary immunodeficiencies are varied and individually uncommon, so diagnosis is often a journey rather than a single answer. Be wary of any service promising an instant diagnosis from one blood test, or selling 'immune system checks' that do not diagnose real immune disease. Make sure you understand which tests are being done, what each result would change, and how you will be followed up. Tell the consultant about any medicines that affect the immune system, as these can change the results.

Published figures to discuss

Primary immunodeficiencies are individually uncommon and very varied, so a single 'accuracy' or 'success' figure is not meaningful. Tests are interpreted together and sometimes repeated, because results can be affected by infection, medicines, vaccines and timing. The notes below are broad and for context only, not precise predictions for you.

These are literature figures, not a personalised prediction. Your own risks and likely benefits depend on your circumstances, your health, and how your care is carried out and followed up.

What happens afterwards

There is no physical recovery from the testing itself. 'Afterwards' is about completing the tests — including the return visit for vaccine-response testing — waiting for results, and following the plan, which may develop as the picture becomes clearer.

• Not having a complete answer at the first appointment
• Several rounds of blood tests, sometimes weeks apart
• A return visit for vaccine-response testing about four weeks after a vaccine
• Waiting for genetic or specialised results that take longer
• A plan that develops as results come back

Aftercare

• Complete all requested blood tests, including the return visit for vaccine-response testing.
• Keep a record of any infections and treatments to bring to follow-up.
• Follow any preventive plan, such as vaccines or preventive antibiotics, as advised.
• Seek medical help promptly for new infections, especially if you have a known or suspected immune problem.
• Tell other clinicians about your immune assessment, particularly before vaccines or immune-suppressing treatment.
• Encourage blood relatives to be assessed if an inherited condition is confirmed.
• Attend follow-up so results can be reviewed and the plan updated.

• Timeline of infections prepared and kept up to date
• Initial blood tests completed
• Return visit for vaccine-response testing booked
• Family history details provided
• Medicine list, including immune-affecting drugs, shared
• Plan for seeking help with new infections clear
• Follow-up appointment booked

⚠ Get urgent help if…

• A high fever with feeling very unwell, especially with a known or suspected immune problem
• A severe or rapidly spreading infection, or one not responding to treatment as expected
• Breathlessness, chest pain or coughing up blood
• Signs of sepsis: confusion, very fast breathing, mottled or pale skin — call 999
• Persistent fevers, drenching night sweats or unexplained weight loss
• Repeated infections needing intravenous antibiotics or hospital admission

Who to contact: your clinician, clinic or test provider first (keep their number to hand). For urgent advice when you can't reach them, call NHS 111. In an emergency, call 999.

General guidance — it doesn't replace the specific advice your specialist gives you.

Results & realistic expectations

A good outcome is a clear answer about whether an inherited immune problem is behind your infections and, where one is found, a diagnosis specific enough to guide treatment and prevention. For many people, the result is reassurance that their immune system is working normally, with sensible advice on preventing infections.

The process cannot always give an immediate diagnosis, and some immune conditions are identified only after testing over time or are never fully explained. A normal set of tests is reassuring, but it is interpreted alongside your history, and occasionally tests are repeated to be sure. A normal result does not promise you will never get infections — it means an inherited immune problem is unlikely to be the cause.

Many primary immunodeficiencies are lifelong, so a confirmed diagnosis usually leads to ongoing treatment and monitoring at a specialist centre. Even after a normal assessment, you should seek review if your pattern of infections changes, because some conditions appear or are recognised later. Where genetic testing is negative but suspicion remains, re-testing may be considered in future as knowledge and technology improve.

Related tests, treatments or support

Diagnosis is often combined with input from other specialists depending on the findings — for example respiratory medicine for recurrent chest infections and lung damage (bronchiectasis), gastroenterology for bowel problems, or haematology. It may also be combined with allergy assessment, as some people have overlapping immune and allergic problems.

Follow-up & long-term care

Follow-up is arranged to review results and decide on treatment, and continues long-term for confirmed conditions. Routine results come back within days to weeks; vaccine-response, specialised and genetic tests take longer and some need repeating. Ask who to contact if you develop a significant infection while your assessment is ongoing.

• Attend regular review for confirmed immune conditions
• Keep vaccinations up to date as advised by your immunologist (some live vaccines may be avoided)
• Continue any preventive treatment, such as antibiotics or immunoglobulin replacement, as planned
• Monitor and report changes in your pattern of infections
• Keep blood relatives informed and assessed where an inherited condition is found

Repeat, follow-on and what comes next

• Diagnoses are often refined as results return and tests are repeated.
• Some conditions are reclassified or only identified with longer follow-up or genetic testing.
• A negative genetic test does not always exclude an inherited condition, and re-testing may be considered in future.
• Treatment plans are reviewed and adjusted over time as the picture and the person's needs change.

Ask what happens if the result is unclear or needs repeating, and what is included if further tests or follow-up are needed.

What good aftercare looks like

• A clear plan of which tests are being done and what each would change.
• A named contact and route for results and for new infections.
• Coordinated long-term follow-up at a specialist centre for confirmed conditions.
• Up-to-date, individualised vaccination and infection-prevention advice.
• Genetic counselling and assessment of relatives where an inherited condition is confirmed.

What affects the cost

Costs vary a great deal between people and providers, and we don't publish prices. What matters is understanding what drives the cost and making sure your quote is complete. The main things that affect it:

• Length and complexity of the consultation
• The range of blood tests requested, including immunoglobulin levels and IgG subclasses
• Vaccine-response testing, which needs a vaccine and a repeat blood test
• Specialised tests such as flow cytometry, complement or neutrophil function
• Genetic testing and any associated counselling
• Repeat testing where results need confirming, and follow-up appointments

• The consultant's appointment fee
• Which tests are included and the cost of specialised or genetic tests
• The cost of the vaccine and the return visit for vaccine-response testing
• Cost of repeat testing if results are unclear
• Cost of follow-up appointments and ongoing monitoring
• Whether onward referral or specialist treatment is included
• What happens, and what it costs, if the work-up is inconclusive, and the cancellation policy

On the NHS? Diagnosis of primary immunodeficiency is provided on the NHS when clinically indicated, with specialist centres for complex conditions; private appointments may be used for speed or a second opinion.

You're entitled to your total cost in writing — including reports, follow-up and what happens if the result is inconclusive — before you decide.

Consent traps and marketing red flags

These are not small details. They are often where patients lose choice, time to reflect, or realistic expectations.

Choosing a specialist safely

• Check the specialist is on the GMC Specialist Register for this area.
• Make sure they work at a CQC-registered service, and look for membership of the relevant Royal College or professional body.
• You're entitled to time to consider and to have your questions answered before you agree — the specialist who looks after you should explain it, not a salesperson.
• Be wary of pressure: time-limited offers or deposits taken before you've had time to think are red flags, not bargains.
• You're entitled to your total cost in writing — including any follow-up — before you decide.

How Vuemedics verifies every consultant →

Take this to your consultation. A good specialist will welcome every one of these.

• Based on my history, do you think an inherited immune problem is likely?
• Which tests are you requesting, and what would each result change?
• Will I need a vaccine and a return visit to test how my antibodies respond?
• How long should this take, and which tests might need repeating?
• Could any of my medicines be affecting the results?
• If you find a primary immunodeficiency, what treatment and monitoring would I need, and should my relatives be tested?
• Are you on the GMC Specialist Register for this area, and which Royal College or professional body are you a member of?
• Will you be the specialist who carries out my test, and who looks after me afterwards?
• What are the risks for someone like me, and how often do your own patients have a problem or need it repeated or redone?
• What does a realistic result look like — and what can this test not achieve?
• What are my options, including waiting, doing nothing for now, or choosing a different approach?
• Can I have written information, results and aftercare instructions in a format I can use, including any accessibility or communication support I need?
• What is the total cost in writing, including any follow-ups, and how much time do I have to decide?

Find a verified specialist for primary immunodeficiency diagnosis

Every consultant is GMC-checked and independently reviewed. Search by postcode and distance, or switch to a map. Ordered by rating, relevance and recency — never by who pays.

How we made this page

Medically reviewed by a GMC-registered consultant. Written in plain English, checked against NHS, NICE, GMC and relevant Royal College / specialist-society guidance, and kept under review. No clinic paid to appear on this page, and we publish no pricing. This is general information to help you prepare — it is not a substitute for advice from your own clinician. How we review our guides →

Source hierarchy: UK regulator and NHS/NICE guidance first, then relevant Royal College or specialist-society guidance, then peer-reviewed evidence for procedure-specific figures where available.

Sources & standards: UK Primary Immunodeficiency Network (UKPIN) Immunodeficiency UK — symptoms and diagnosis Diagnostic tests for primary immunodeficiency (classic and genetic) — PMC Primary immunodeficiency overview — PMC Evaluation of the 10 warning signs of primary immunodeficiency — PMC NHS — Sepsis (urgent help with infection)

Reviews reflect patients' experience of care, not clinical outcomes. For procedure volumes and outcome data see PHIN.

Last medically reviewed 2026-09-21. Spotted something wrong or out of date? Report an error in this guide.