In the diagnosis of HIV infection in infants born to HIV-positive mothers, which test is recommended in the first 6 weeks of life, and why is serology (ELISA) unreliable at this age?
- A HIV p24 antigen ELISA; because T-cell counts are unreliable in infants
- B HIV serology is reliable at 6 weeks as maternal antibodies are cleared by then
- C Western blot; because ELISA is not approved in children under 2 years
- D HIV-1 DNA PCR on dried blood spot; because maternal IgG crosses the placenta and persists in the infant until 12–18 months, causing false-positive ELISA results ✓
Explanation
Maternal IgG antibodies (including anti-HIV IgG) cross the placenta and persist in the infant's circulation for 12–18 months. Therefore, ELISA-based HIV antibody tests cannot distinguish maternal from infant antibodies during this period, causing false-positive results even in uninfected infants. HIV-1 DNA PCR (on peripheral blood mononuclear cells or dried blood spot/DBS) directly detects proviral HIV-1 DNA in the infant's cells and is positive from birth in infected infants. The Early Infant Diagnosis (EID) program recommends HIV DNA PCR at 6 weeks, 6 months, and 12 months. p24 antigen testing is less sensitive than PCR in infants.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
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Written and medically reviewed by the StethoPrep medical team.