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Ch. 6 - Viruses and Prions
Norman-McKay- Microbiology: Basic and Clinical Principles 2nd Edition
Norman-McKay2nd EditionMicrobiology: Basic and Clinical PrinciplesISBN: 9780137661619Not the one you use?Change textbook
All textbooksNorman-McKay 2nd EditionCh. 6 - Viruses and PrionsProblem 12
Chapter 6, Problem 12

A young man comes into your clinic and asks for an HIV test. He had unprotected sex two weeks ago and is nervous. His best option would be a(n):
a. ELISA of anti-HIV antibodies
b. Test that detects HIV genes
c. Latex agglutination test
d. Cell culture of blood sample

Verified step by step guidance
1
Step 1: Understand the window period of HIV infection. After exposure to HIV, the body takes some time to produce detectable antibodies, usually several weeks. Testing for antibodies too early may result in a false negative.
Step 2: Review the types of HIV tests available. Antibody tests (like ELISA) detect the body's immune response, while tests that detect HIV genes (such as nucleic acid tests, NAT) can identify the virus itself earlier in infection.
Step 3: Consider the timing of the test. Since the patient had unprotected sex only two weeks ago, antibody tests may not yet be reliable because antibodies might not have developed.
Step 4: Recognize that tests detecting HIV genetic material (e.g., PCR or NAT) can detect infection earlier than antibody tests, making them more suitable for early diagnosis.
Step 5: Evaluate the other options: latex agglutination and cell culture are less commonly used or take longer, so the best option for early detection is a test that detects HIV genes.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Window Period in HIV Infection

The window period is the time after HIV exposure during which the virus is present but antibodies are not yet detectable. This period typically lasts several weeks, so antibody-based tests like ELISA may yield false negatives if done too early. Understanding this helps determine the most appropriate test shortly after exposure.
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Types of HIV Diagnostic Tests

HIV tests include antibody tests (e.g., ELISA), nucleic acid tests (NAT) that detect viral RNA or genes, antigen tests, and culture methods. NATs can detect HIV earlier than antibody tests because they identify the virus directly, making them preferable soon after exposure.
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Sensitivity and Practicality of HIV Testing Methods

Tests vary in sensitivity, specificity, and turnaround time. ELISA is widely used for screening but less effective early post-exposure. NATs are more sensitive early on but costlier. Cell culture is complex and slow, while latex agglutination is less commonly used. Choosing the right test balances accuracy and feasibility.
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Related Practice
Textbook Question

Which of the following is a potential feature of an animal virus? Select all that apply.

a. Presence of an envelope

b. Presence of a naked icosahedral capsid

c. Ability to inject naked RNA into the host cell

d. Ability to integrate into the host cell’s genome

e. Ability to cause host cell lysis

f. Ability to build DNA from an RNA template

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Textbook Question

Why don’t bacteriophages undergo an “uncoating” step during replication?

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Textbook Question

Which of the following could inform you if your patient had a previous infection with a nonpersistent virus and recovered? Select all that apply.

a. A PCR test

b. A plaque assay

c. An ELISA test

d. An agglutination assay

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