Questions and Answers
How is HIV primarily transmitted?
What is the primary characteristic of viruses when outside a host cell?
What type of virus is HIV categorized as?
What does a positive result look like in a Rapid Assay test for HIV?
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Which laboratory method is NOT commonly used for HIV testing?
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What is the consequence of untreated HIV infection?
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What does a positive anti-dengue IgM test indicate?
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When do IgM antibodies become detectable in patients with dengue?
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How long can high concentrations of NS1 antigens be detected after the onset of illness in dengue patients?
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What is the primary limitation of IgG positivity in dengue diagnosis?
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What is the correct procedure for reading results from a rapid antibody test for dengue?
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What can be inferred about the presence of cross-reactive antibodies in the Flavi virus genera?
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What does a positive IgM and negative IgG result indicate?
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Which hepatitis virus is classified as an RNA virus?
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How is Hepatitis B primarily transmitted?
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What is the incubation period for Hepatitis A?
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Which outcome is likely if both IgM and IgG are negative?
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What type of vaccine is used for Hepatitis A?
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What is a characteristic of Hepatitis A in relation to chronic liver disease?
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What is the typical incubation period for Hepatitis B?
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What is considered a true positive result in the context of antibody testing?
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Which laboratory marker is categorized as progressing to AIDS when CD4+ T-cell counts drop below what level?
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In children younger than 18 months, why are serological tests for HIV infection considered unreliable?
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Which mosquito is primarily responsible for transmitting the dengue virus?
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What type of virus causes dengue fever?
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What is the typical duration of symptoms for dengue fever?
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What is the NS1 antigen used for in the diagnosis of dengue fever?
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What environmental condition increases the risk of dengue fever transmission?
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What is the significance of detecting anti-HBc antibodies in chronic hepatitis B?
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During which stage of hepatitis B infection is HBeAg most likely to be elevated?
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Which serological test offers a qualitative detection of HBsAg in serum?
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Which principle is involved in the ELISA test for detecting HBsAg?
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What does the presence of HBV DNA indicate in a patient?
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What is the typical time frame for detecting anti-HCV IgG in a patient post-infection?
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Which of these tests is a molecular test for hepatitis B diagnosis?
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What method is employed to detect HBsAg using reverse passive hemagglutination?
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Study Notes
Viruses
- Characterized as obligate intracellular parasites, exhibiting life only within host cells.
- Outside host cells, viruses are inert and lack enzymatic activity.
- Inside host cells, viral nucleic acids (DNA or RNA) hijack cellular machinery to replicate and produce new virus particles.
HIV Serology
- HIV compromises the immune system, potentially leading to AIDS if untreated.
- Transmission occurs via blood, sexual contact, and from mother to child during pregnancy, delivery, or breastfeeding.
- Common laboratory testing methods include Rapid tests, ELISA, and RT-PCR.
Common HIV Antibody Tests
- Enzyme Linked Immunosorbent Assays (ELISA) include indirect methods.
- Rapid Tests provide quick results.
- Western Blot is a confirmation test for HIV antibodies.
Rapid Assay Testing Principle
- Antigen is coated onto a test strip with a positive control.
- Sample addition triggers a reaction between antigen and antibody, if present.
- Positive result shows two or three colored bars; negative shows one colored bar; invalid results appear without lines.
- Specificity against viral components is crucial for true positive results.
Laboratory Monitoring for HIV
- Peripheral blood CD4 T-cell count: Levels under 200/µL indicate progression to AIDS.
- HIV-1 RNA level (viral load) is detectable as early as 10 days post-infection; highly sensitive tests like qPCR are employed.
Serology of Dengue Fever
- Dengue is a mosquito-borne viral disease prevalent in tropical and subtropical regions, transmitted by Aedes Aegypti mosquitoes.
- The dengue virus (RNA) is part of the Flavivirus genus; four serotypes exist (DEN-1 to DEN-4).
- Infection with one serotype results in lifelong immunity against that type.
Dengue Fever Symptoms
- High fever (40°C/104°F), severe headache, pain behind the eyes, muscle and joint pain, nausea, vomiting, swollen glands or rash.
- Symptoms are self-limiting, usually lasting 2-7 days.
Laboratory Diagnosis of Dengue
- Virus detection via cell culture, antigen detection, and viral RNA detection within 24-48 hours.
- NS1 glycoprotein antigen can be rapidly detected; a strong humoral response noted.
- IgM antibodies appear first, detectable by days 3-5, reaching 99% detection by day 10.
- IgG levels indicate past infection and remain detectable over months to years.
Rapid Antibody Testing for Dengue
- Simple procedure involves adding patient serum and buffer; results interpreted after 15 minutes.
- Positive IgM and negative IgG indicate a current infection; positive IgG indicates a past infection.
Serology of Hepatitis Tests
- Hepatitis refers to liver inflammation, caused by various viruses, primarily hepatotrophic viruses (A, B, C, D, E).
- Each virus has distinct transmission routes and incubation periods.
Hepatitis A Virus
- RNA virus primarily spread via the fecal-oral route; rare transmission via blood.
- Incubation is around one month; does not cause chronic liver disease.
- Effective vaccine available (formalin-killed HAV).
Hepatitis B Virus
- DNA virus spread through blood, sexual contact, and perinatal routes.
- Approximately 3-month incubation; antibodies against HbcAg detectable.
- HBeAg serves as an indicator of acute or chronic infection.
Serological Testing for Hepatitis B
- Reverse passive latex agglutination and chromatographic techniques used for HBsAg detection, with ELISA being the most common method.
- PCR (qPCR) is a confirmatory test for HBV DNA detection.
Hepatitis C Virus (HCV) Antibody Testing
- Diagnosis is achieved by detecting anti-HCV IgG in serum, usually detectable 6-8 weeks post-infection.
- Anti-HCV testing is critical for screening blood donors.
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Description
Explore the key concepts of viral infections and serological testing as discussed in Chapter 4. This quiz covers the characteristics of viruses, with a focus on HIV and its impact on the immune system. Test your understanding of viral replication and the significance of serology in diagnosing infections.