Which test is used to detect HIV in newborns?

AIIMS CRE 2025

Child Health Nursing (Pediatrics)

Hard

Appeared in: AIIMS CRE 2025

Explanation

RNA PCR is a virologic test that directly detects the genetic material (RNA) of the HIV virus itself.
This method is the gold standard for newborns because it is not affected by the presence of maternal HIV antibodies, which are transferred across the placenta during pregnancy.
Unlike antibody tests, PCR provides a definitive diagnosis by confirming the presence of the virus in the infant's blood, allowing for early treatment.

Option A: This test detects HIV antibodies, not the virus. In a newborn, it will detect the mother's antibodies that crossed the placenta, leading to a false-positive result even if the baby is not infected.
Option B: Similar to ELISA, this is a confirmatory test for HIV antibodies. It will also produce a false-positive result in a newborn due to the presence of maternal antibodies.
Option D: This test does not diagnose HIV. It measures the number of CD4 T-cells to assess the health of the immune system and monitor the progression of the disease in an individual already known to be HIV-positive.

Visual 1: Flowchart: Diagnostic algorithm for an HIV-exposed infant. This visual would show the recommended timeline for PCR testing at birth, 2-3 weeks, 1-2 months, and 4-6 months, and clarify when antibody tests become reliable (after 18 months).

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Diagnostic testing for HIV in newborns as background academic context rather than a clinical decision trigger.
Early and accurate diagnosis of HIV in newborns using PCR is critical to initiate antiretroviral therapy (ART) promptly, which significantly reduces the risk of disease progression and mortality.
Nurses are central to educating parents about the complex testing schedule, the meaning of the results, and the absolute importance of adherence to prophylactic ART for the infant.
What if? If the child being tested was 3 years old instead of a newborn, an ELISA antibody test would be the appropriate initial screening test, as any maternal antibodies would have disappeared by that age, making the test reliable.

How to Approach the Question

First, identify the specific patient population in the question: 'newborns'.
Recall the key physiological factor for this population regarding HIV: the passive transfer of maternal antibodies across the placenta.
Analyze the options based on this key fact. Ask yourself: 'Which test is affected by maternal antibodies?'
Eliminate antibody-based tests (ELISA, Western blot) because they will produce false-positive results due to detecting the mother's antibodies.
Differentiate between a test that diagnoses an infection (detects the pathogen) and one that monitors the disease (assesses its effect). Eliminate CD4 count as it is a monitoring tool.
Conclude that the correct test must be one that detects the virus directly, bypassing the antibody issue. This leads to RNA PCR.

Concept Tested & Keywords

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