Early infant HIV diagnosis — DTM&H MCQ

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ModerateHIV/AIDS in tropical settingsEarly infant HIV diagnosisDTM&H

A 6-week-old infant in a rural clinic was born to a mother with HIV who started ART late in pregnancy and is breastfeeding. The infant is clinically well. What is the most appropriate investigation?

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Correct answer: A — HIV nucleic acid test for early infant diagnosis

The correct answer is A, HIV nucleic acid test for early infant diagnosis. Maternal IgG antibody crosses the placenta and can persist up to 18 months, so any antibody assay in this infant reflects the mother's status, not the child's. WHO recommends virological (nucleic acid, PCR based DNA or RNA) testing from six weeks of age for HIV exposed infants, as vertically acquired virus is reliably detectable at this point despite ART prophylaxis. This infant carries added risk from late maternal ART initiation and ongoing breastfeeding, but the indicated step at six weeks remains a nucleic acid test regardless of clinical wellness. WHO recommends that national programmes should establish the capacity to provide early virological testing of HIV-exposed infants at six weeks or as soon as possible thereafter to guide clinical decision-making at the earliest possible stage. Why the other options are wrong: B. HIV antibody test as definitive diagnosis: maternal antibody persists well beyond six weeks, so a positive result reflects maternal exposure, not the infant's own status; antibody testing is only diagnostic after 18 months or after breastfeeding cessation plus the window period. C. CD4 count as the diagnostic test: CD4 count monitors immune status in confirmed infection, it neither detects virus nor antibody and cannot establish diagnosis. E. Western blot after breastfeeding stops: this is an antibody confirmatory assay, and deferring testing until breastfeeding ends would miss the window for prompt ART initiation. D. p24 antigen after 5 years: not a standard early infant diagnostic tool, and a five year delay is indefensible given high early mortality in untreated perinatal infection. Key point: Maternal antibody makes serology unreliable before 18 months, so virological testing from six weeks of age is the diagnostic test of choice in HIV exposed infants, regardless of breastfeeding status or clinical wellness.

Reference: World Health Organization, Consolidated Guidelines on HIV Testing Services / Recommendations on the Diagnosis of HIV Infection in Infants and Children: early virological (nucleic acid) testing from 6 weeks of age for HIV-exposed infants. https://www.ncbi.nlm.nih.gov/books/NBK138550/