Which of the following is the confirmatory test of AIDS?

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Explanation

The Western Blot test is a highly specific immunological test used to confirm the results of a positive screening test for HIV, such as the ELISA.
It works by detecting antibodies in the patient's serum that are directed against specific HIV viral proteins (e.g., p24, gp41, gp120/160).
Its high specificity is crucial for ruling out false-positive results from the more sensitive but less specific screening tests.
Historically, it has been the gold standard for confirming an HIV diagnosis following a reactive screening assay.

Option A: The VDRL (Venereal Disease Research Laboratory) test is a non-treponemal test used for screening for syphilis, not HIV/AIDS.
Option C: ELISA (Enzyme-Linked Immunosorbent Assay) is the primary screening test for HIV, not the confirmatory test. It is highly sensitive but can produce false-positive results.
Option D: The CD₄ count measures the number of CD₄ T-lymphocytes. It is used to assess the stage of HIV disease, monitor the progression of the infection, and evaluate the effectiveness of antiretroviral therapy. It does not diagnose the presence of the virus itself.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Diagnostic testing for HIV/AIDS as background academic context rather than a clinical decision trigger.
Understanding the difference between screening and confirmatory tests is critical for nurses in patient education and counseling. A positive screening test does not mean a definitive diagnosis.
Nurses must be prepared to explain the testing process to anxious patients, emphasizing that a confirmatory test is needed to be certain of the diagnosis, thereby preventing undue stress and misinformation.
What if a patient has a positive ELISA but a negative or indeterminate Western Blot? The nurse should understand that this requires follow-up testing, often including a repeat test after a few weeks or a viral load (PCR) test, as the person might be in the early 'window period' of infection before a full antibody response has developed.

How to Approach the Question

First, identify the key term in the question: 'confirmatory test'. This indicates you are looking for a test that definitively diagnoses a condition, usually after a preliminary screening test.
Next, analyze the options in the context of HIV/AIDS diagnosis.
Recall or deduce the purpose of each test. ELISA is a common screening tool due to its high sensitivity.
Recognize that a highly specific test is needed to confirm a positive screen. The Western Blot serves this purpose for HIV.
Eliminate the other options based on their functions: VDRL is for a different disease (syphilis), and CD₄ count is for monitoring disease progression, not for initial diagnosis.

Concept Tested & Keywords

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