In an infant born to a HIV infected mother, at what age of child the ELISA test can reliably diagnose HIV infection?
**Core Concept**
The diagnosis of HIV infection in infants is challenging due to the presence of maternal antibodies, which can interfere with serological tests. The age at which an infant can be reliably diagnosed with HIV infection is crucial for initiating antiretroviral therapy.
**Why the Correct Answer is Right**
The ELISA test, a widely used serological test for HIV diagnosis, detects the presence of antibodies against HIV. However, in infants born to HIV-infected mothers, these antibodies are of maternal origin and can be present for up to 18 months after birth. The correct answer is 18 months because, at this age, most maternal antibodies have been cleared, and the infant's immune system has begun to produce its own antibodies against HIV. This allows for a more accurate diagnosis of HIV infection.
**Why Each Wrong Option is Incorrect**
**Option A:** 6 months - At 6 months, maternal antibodies are still present, and the ELISA test may yield false-positive results.
**Option B:** 12 months - While some maternal antibodies may have been cleared, the ELISA test may still be influenced by residual antibodies, leading to inaccurate results.
**Option C:** 24 months - This option is too conservative, as most maternal antibodies are cleared by 18 months, and the ELISA test can reliably diagnose HIV infection at this age.
**Clinical Pearl / High-Yield Fact**
Infants born to HIV-infected mothers should be tested for HIV at 4-6 weeks, 3-4 months, and 12-18 months of age. The results of these tests should be interpreted in the context of the infant's clinical presentation and other laboratory findings.
**Correct Answer:** C. 18 months.