Explaining an HIV-exposed infant's diagnosis and feeding plan — OSCE

Candidate instructions (8-minute station)

You are the paediatric registrar on the postnatal ward. A term, well infant has just been born to a 28-year-old mother who was diagnosed with HIV at 24 weeks of pregnancy and started on combination antiretroviral therapy; her viral load is now suppressed. [7]

Your tasks are: [7]

1. Explain why the baby's HIV antibody test will be positive but does not mean the baby is infected, and how infection will actually be confirmed or excluded. [7]
2. Explain the infant's medication — nevirapine prophylaxis and, from a few weeks, cotrimoxazole — and what each is for. [7] [8]
3. Explain the HIV PCR testing schedule, including the final antibody test at 18 to 24 months. [7]
4. Advise on infant feeding, and explain how the mother's own viral suppression is the most important protection for the baby. [3] [7]

You are not expected to adjust the mother's own HIV medications — her HIV physician retains that — but you should reinforce the importance of her staying on treatment and engaged in care. [7]

Examiner prompt to the actor (mother)

"But the midwife said the baby would test positive — doesn't that mean he's got it? And I so wanted to breastfeed — my sisters all breastfed. Why does he need medicine if he's not even sick? You're telling me I have to keep taking my own tablets too — is all of this really necessary?" [7]

Marking domains

• Understanding the test (3): explains clearly that maternal antibody crosses the placenta and lingers for up to 18 months, so a positive antibody test reflects the mother not the infant; names that the baby's infection is confirmed or excluded by HIV DNA/RNA PCR, with a second sample confirming any positive; reassures that the baby may well be uninfected. [7]
• Prophylaxis and the PCR plan (3): explains nevirapine prophylaxis and cotrimoxazole as protection through the window until infection is excluded or confirmed; outlines the PCR schedule (around six weeks, with follow-up testing) and the final antibody test at 18 to 24 months. [7] [8]
• Feeding and maternal suppression (3): in a setting where safe replacement feeding is reliably available, advises exclusive formula feeding and explains that breastfeeding by an HIV-positive mother carries a transmission risk that her suppression reduces but does not eliminate; reinforces that the mother's own undetectable viral load is the single strongest protection for the baby and that staying on her treatment is essential. [3] [7]
• Communication (1): acknowledges the mother's anxiety and her wish to breastfeed without judgment, uses plain language, checks understanding, and does not overwhelm. [7]

Model answer — the explanatory script

"Congratulations on your baby — he's doing beautifully. I want to take a few minutes to explain exactly what happens next, because I know you've been told the baby will test positive, and I can see that's frightening you. Let me start there." [7]

"The test that will come back positive is an antibody test. Antibodies are little signals your immune system makes — and yours, because you have HIV, include HIV antibodies. During pregnancy, those antibodies cross the placenta into the baby, and they stay in his blood for up to about 18 months. So when we test him and it comes back positive, that's your antibody we're seeing — it tells us about you, not about him. It does not mean he has HIV. To know whether the baby himself has the virus, we have to look for the virus directly, with a different test called a PCR — and that's the test that actually matters." [7]

"So here's the plan. We'll give the baby a short course of a medicine called nevirapine for about six weeks — it's a preventative, to stop the virus taking hold in those early weeks, and from about four to six weeks we'll add a second preventative medicine, cotrimoxazole, which protects him against a particular pneumonia that HIV-exposed babies can get. Neither of these means he's sick — they're there to keep him well through the window until we know for certain." [7] [8]

"Then we test. We'll do the PCR — the virus test — at around six weeks. If it's negative, that's reassuring, but because there can be a lag we'll repeat testing and then do a final antibody test at around 18 to 24 months, by which time your antibody will have cleared from his blood and the test will finally tell us about him. If any PCR is positive, we confirm it with a second test before we say he's infected — and if he were infected, we would start treatment straight away, because treating babies early saves lives." [7]

"Now, feeding. I know you wanted to breastfeed, and I understand why — it's a natural thing to want. The honest answer is that, here, where we have clean water and reliable formula, we advise exclusive formula feeding, because breastfeeding can pass the virus even when you're on treatment. Your own tablets are the most important protection of all: a mother whose viral load is undetectable has a better than 98% chance of an uninfected baby, and that undetectable viral load is the single biggest reason your baby is likely to be fine. So the most protective thing you can do for him is to keep taking your own medicine and stay connected with your HIV doctor — that's what keeps the virus suppressed, and a suppressed mother is the best protection a baby can have." [3] [7]