Which technique is used to detect HIV infection?

Raj. CHO -2020

Applied Microbiology & Infection control

Easy

Appeared in: Raj. CHO -2020

Explanation

The standard diagnostic algorithm for HIV involves a two-step process: a highly sensitive screening test followed by a highly specific confirmatory test.
ELISA (Enzyme-Linked Immunosorbent Assay) is the primary screening test. It detects antibodies to HIV and/or the p24 antigen and has a sensitivity exceeding 99.5%, making it excellent for initial screening.
A positive ELISA result must be confirmed to rule out a false positive. The Western blot is the classic confirmatory test used for this purpose.
The Western blot is highly specific because it identifies antibodies directed against individual, specific HIV proteins (e.g., gp41, p24), thus confirming the presence of a true infection.

Option A: The Northern blot technique is used to detect and analyze specific RNA molecules in a sample, not proteins or antibodies related to HIV for diagnostic purposes.
Option B: While a Western blot is a type of immunoblot, the term 'Western blot' is the specific and universally accepted name for the HIV confirmatory test. 'Immunoblot' is too general and less precise.
Option C: The Southern blot technique is used to detect specific DNA sequences. It is not used in the diagnosis of HIV, which primarily involves detecting antibodies or viral RNA/antigens.

Visual 1: Flowchart: A flowchart illustrating the two-step HIV testing algorithm, starting with the ELISA screening test. If positive, it leads to the Western blot confirmatory test. If negative, no further action is needed (unless recent exposure is suspected).
Visual 2: Infographic: An infographic titled 'SNoW DRoP' visually explaining the three main blotting techniques: Southern (DNA), Northern (RNA), and Western (Protein), with simple icons for each molecule.
Visual 3: Diagram: A simplified diagram showing how the Western blot works, with lanes for different HIV proteins and bands appearing where patient antibodies have bound, confirming the infection.

Clinical Relevance

Nursing practice connection: Knowing Diagnostic techniques for HIV infection helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
The two-step testing protocol (sensitive screening followed by specific confirmation) is a critical public health strategy to ensure accurate diagnosis, prevent the psychological distress of false-positive results, and ensure that individuals who are truly positive receive timely care.
Nurses must be able to explain the 'window period' to patients. This is the time after infection (typically 3-12 weeks) when a person may have HIV but test negative because their body has not yet produced enough antibodies to be detected by an ELISA test.
What if? If a patient has a positive ELISA but a negative or indeterminate Western blot, they should be re-tested in a few weeks. This could indicate a false-positive ELISA, or it could be a very early infection where the full antibody response has not yet developed.

How to Approach the Question

First, identify the core of the question: it asks for the standard techniques to 'detect' HIV.
Recognize that diagnosing major infectious diseases like HIV often involves a multi-step process, typically a screening test followed by a confirmatory test.
Recall or deduce the standard tests for HIV. ELISA is widely known as a screening test for many conditions. The blot techniques are more specific.
Use the 'SNoW DRoP' mnemonic to differentiate the blotting techniques: Southern for DNA, Northern for RNA, and Western for Protein. Since HIV diagnosis involves detecting antibodies (proteins), Western blot is the correct choice for confirmation.
Evaluate the options. Option D combines the standard screening test (ELISA) with the standard confirmatory test (Western Blot), making it the most complete and accurate answer.

Concept Tested & Keywords

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