Explaining a primary immunodeficiency diagnosis and immunoglobulin replacement — OSCE

Candidate instructions (8-minute station)

You are the paediatric registrar in the general paediatric clinic. An eight-year-old girl has been referred for recurrent otitis media, sinusitis and pneumonia, with two hospital admissions in the past year and new crackles and wheeze suggesting early bronchiectasis. Her blood tests show low IgG and IgA and a poor response to a pneumococcal vaccine challenge, and the immunology team has confirmed a diagnosis of common variable immunodeficiency — a primary antibody deficiency. [7]

Your tasks are: [1]

1. Explain the diagnosis of common variable immunodeficiency in language the family can understand. [7]
2. Explain why immunoglobulin replacement therapy is needed, what it involves practically, and what it will and will not achieve. [7]
3. Cover the infection-prevention and vaccination strategy, including which vaccines are safe and which need coordination with immunology. [5]
4. Address the genetic counselling, the school and transition plan, and the father's belief that the recurrent infections were "just a phase". [1]

You should name the immunology team as the long-term lead for her care and explain what ongoing surveillance will involve. [5]

Examiner prompt to the actors (parents)

Mother: "Is this something she was born with? Did we miss something when she was little? And will she always need this treatment — the replacement you're describing?" [7]

Father: "Look, kids get sick — she's been in daycare and school, she's just one of those kids who catches everything. Are you sure this isn't just a phase she'll grow out of? I don't want her on medicine for the rest of her life." [1]

Marking domains

• Frame and reassurance (3): sets a calm, empathetic tone; acknowledges that recurrent infection is common in children and that reaching this diagnosis takes persistence; explains clearly that this is a real, identifiable condition of the immune system and that effective treatment exists; does not dismiss the father's view but reframes it with the test results. [7]
• Explaining the diagnosis (3): explains that the immune system makes proteins called antibodies that fight bacteria, and that her body is not making enough of the type that protects the lungs and sinuses, which is why she keeps getting the chest and ear infections; names common variable immunodeficiency; confirms it is an inborn error of immunity, not caused by anything the family did or missed. [7]
• Treatment and surveillance (3): explains that immunoglobulin replacement gives her the antibodies her body cannot make, regularly — intravenous in hospital or under the skin at home — so that the infections stop and her lungs are protected from further damage; names that it does not cure the underlying cause but controls it; describes ongoing respiratory surveillance, the immunology team as the long-term lead, and that treatment is lifelong. [5]
• Addressing the parents and the plan (1): addresses the father's "just a phase" belief by using the abnormal test results and the emerging bronchiectasis as the evidence that this is not a self-limiting pattern; addresses the mother's question about whether it was missed by explaining the diagnosis is often delayed precisely because recurrent infection is so common in children; covers genetic counselling, the school plan, and transition. [1]

Model answer — the explanatory script

"Thank you both for coming in. I want to take you through what we've found, what it means for your daughter, and what we can do about it — because the good news is that this is a condition we understand and we can treat very effectively. The tests have shown us why she has been getting so many chest and ear infections, and that's actually a relief, because now we know what we're dealing with." [7]

"Your daughter's immune system is the body's defence against infection, and one part of it makes proteins called antibodies — think of them as little soldiers that hunt specific bacteria. Her body is not making enough of the antibodies that protect the lungs, sinuses and ears from the common bacteria that cause pneumonia and ear infections. That's why she's had so many infections and why two of them were bad enough to need hospital. It has a name — common variable immunodeficiency — and it's something she was born with, a small difference in how her immune system is built. It is not caused by anything you did or didn't do, and it's not something you missed when she was little. These conditions are often picked up late precisely because every child gets coughs and colds, and it can take a while for the pattern to become clear." [7]

"I understand you're wondering whether this is just a phase she'll grow out of. I want to be straight with you, because that's what she deserves. The blood tests show clearly that her antibody levels are low and that her body doesn't respond to a vaccine challenge the way it should, and we're already seeing the early signs of damage to her airways — that's the bronchiectasis I mentioned. Those are objective findings, not a guess, and they tell us this isn't something she'll simply outgrow. But — and this is the important part — we have a treatment that replaces exactly what's missing, and it works very well." [1]

"The treatment is called immunoglobulin replacement. We give her the antibodies her body can't make — they're collected from donors and purified very carefully. She can have it through a drip in hospital every few weeks, or, if you prefer, under the skin at home once you're trained. The aim is to keep a steady level of antibodies in her blood so that the infections stop and her lungs are protected from any further damage. It doesn't cure the underlying condition — she'll need this treatment long-term — but it controls it, and most children on it live full, normal lives and go to school, play sport and do everything their friends do. We'll watch her lungs with breathing tests and scans to make sure the treatment is working." [7]

"One thing you'll hear from the immunology team is about vaccines. Most vaccines are absolutely fine and important for her — the flu vaccine each year, for example. But because her immune system works differently, we coordinate some vaccines with the immunology team, and in particular any live vaccine is something we hold off on until they've confirmed it's safe. That's a routine precaution for children with this condition, and the team will give you a clear written plan so you and the school know exactly what's safe." [5]

"You asked whether she was born with this and whether it runs in families. Common variable immunodeficiency is an inborn error of immunity, and sometimes there is a genetic pattern, so the team will offer genetic counselling — that's a conversation with a specialist about whether other family members should be tested and about what this means for the future. It doesn't mean everyone in the family is affected, but it's worth having the conversation properly." [1]

"So to finish: this is a real, identifiable condition, not a phase; we have an effective treatment in immunoglobulin replacement; the immunology team will lead her long-term care with us; and we'll make sure her school has a plan and that you have a written summary of everything we've talked about. She's going to be on treatment for the long term, but with it, she can expect to do well. Does that all make sense, and is there anything you'd like me to go over again?" [5]