Dr. Ira Shah
Incharge Pediatric HIV and TB Clinic, B.J.Wadia Hospital for Children, Mumbai, India Consultant in Pediatric Infectious Diseases, Nanavati Hospital, Mumbai, India

Diagnosis of HIV in infants
All infants born to HIV-infected mothers carry maternal IgG antibodies which cross the placenta freely. These maternal antibodies may remain detectable in the infant’s serum for up to 12–15 months after birth. As a result, serological diagnosis of HIV infection is only reliable after 15-18 months of age. Infants infected with HIV must be diagnosed as rapidly as possible to ensure the early institution of therapy to limit HIV related morbidity and to prevent opportunistic infections. Tests that can be done for diagnosis of HIV infection in children below 18 months of age are HIV culture, detection of HIV proviral DNA by polymerase chain reaction (PCR) or HIV antigen (p24). Detection of p24 antigen is cheaper, highly specific and easy to perform but it is less sensitive than other virologic tests. Also false negativity is high in younger children as most of the p24 antigen is bound to maternal antibodies. PCR is now the preferred tool for diagnosis of HIV in infants.

HIV Culture
HIV culture is done from peripheral blood mononuclear cells (PBMCs) but is technically difficult and time consuming. It is expensive and done in research institutes. Positive results are available by 1-2 weeks but negative results are not reported till there is no evidence of HIV replication for 30 days. Sensitivity for detecting infection has been reported to be 50% at birth and 90% by 3 months of HIV. However a single test is not conclusive of the diagnosis and should be confirmed by a repeat test or PCR test.