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HIV Diagnosis and Testing

HIV Diagnosis and Testing. HAIVN Harvard Medical School AIDS Initiatives in Vietnam. Learning Objectives. By the end of this session, participants should be able to: Explain the importance of HIV voluntary counseling and testing (VCT) Describe the “window period”

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HIV Diagnosis and Testing

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  1. HIV Diagnosis and Testing HAIVN Harvard Medical School AIDS Initiatives in Vietnam

  2. Learning Objectives By the end of this session, participants should be able to: • Explain the importance of HIV voluntary counseling and testing (VCT) • Describe the “window period” • Outline the different tests used to diagnose HIV infection • Describe the Vietnam MOH testing strategy

  3. What is VCT and Why is it Important?

  4. VCT Key Principles Voluntary: Client makes own decision whether to take HIV test Counseling: HIV testing always accompanied by HIV prevention counseling Testing: Test results must be provided in accordance with current MOH guidelines

  5. Why is VCT Important ? VCT serves as an entry point for: Client acceptance Of serostatus Early management of OIs Referrals to care and treatment services including ART Reduction in mother-to child transmission VCT Referrals to social and peer support Facilitation of Behavior change Preventive therapy and contraceptive advice

  6. MOH Guidelines for VCT Pre-test session Post-test session HIV test • Provide: • test result • support around partner notification • emotional support • referrals • Discuss risk reduction plan • Assess client knowledge • Assess client risk • Create risk reduction plan with client • Prepare HIV test • Refer for services • Conduct HIV test • Done off-site in MOH approved labs • Client tries out risk reduction plan

  7. VCT for Special Populations Sex Workers STI Patients Drug Users Special populations TB Patients Men having Sex with Men (MSM) Pregnant Women

  8. Window Period (1) • HIV antibodies take time to multiply and show up on antibody tests • The window period is the period between time of infection and when initial detection of HIV markers is possible by laboratory tests • Influenced by the HIV marker, the assay and by individual patient

  9. Window Period (2) • The majority of infected individuals test positive by antibody test 1-3 months after infection • However, the window period can last as long as 3 to 6 months • Especially true for patients with Hepatitis C co-infection

  10. HIV Testing and the “Window Period” Window period CD4 HIV Antibody Detectable antibody level Viral Load 1234567-12 1 2 3 4 5 6 7 8 9 10 11 12 13 weeks years

  11. Serologic Tests to Diagnose HIV Infection

  12. Overview of HIV Testing Methods • Antibody tests • Rapid Test • ELISA • Western Blot • Direct HIV Tests • Polymerase Chain Reaction (PCR) • Demonstration of viral antigen (p24 antigen) • Early Infant Diagnosis • Dry Blood Spot

  13. ELISA _ + _ + Positive Negative Read results immediately HIV Antibody Tests (1) “Rapid test” Western Blot _ +

  14. HIV Antibody Tests (2) Rapid ELISA/Rapid EIA (“Rapid Tests”) • Results in 10 minutes to 2 hours using blood, urine or saliva • Extremely useful for immediate results • Many different tests are available with excellent sensitivity and specificity • Negative test can be reported as negative • Positive results must be confirmed with additional testing

  15. HIV Antibody Tests (3) Western Blot Test (WB) • Used as a confirmatory test • Very specific for HIV • Samples that give a negative result are reported as negative

  16. Direct HIV Tests (1) Polymerase Chain Reaction (PCR) • Detects HIV genetic material in blood • Positive within 1-2 weeks after infection • Babies born to HIV positive mothers may be tested by looking for HIV DNA • Can be used to diagnose acute HIV infection in adults during window period

  17. Direct HIV Tests (2) Demonstration of viral antigen (p24 antigen) • Sometimes used to screen donated blood • Can also be used to test for HIV in individuals, mostly children • Detectable within 2-3 weeks after infection • Becomes negative after seroconversion and development of anti-p24 antibodies

  18. Dry Blood Spot (DBS) Test (1) • DBS is used to facilitate testing of HIV DNA for the purposes of early infant HIV diagnosis • A DBS is a sample of whole blood collected on filter paper and dried • DBS can be stored and shipped to testing facilities • Using DBS, infants can be tested using PCR as early as 4-6 weeks of age.

  19. Dry Blood Spot (DBS) Test (2)

  20. Testing Strategies

  21. MOH Testing Strategies

  22. Interpretation of HIV Test (1)Adults and Children > 18 Months

  23. Interpretation of HIV Test (2)Children < 18 Months Confirmation of HIV infection requires: • Infants less than 9 months • Two positive PCR tests • Performed between 4-6 weeks, or ASAP • Breastfeeding stopped completely for more than 6 weeks • Infants between 9-18 months • Testing for antibody first • Confirmed with PCR test

  24. Small Group Activity

  25. Key Points • “Window period” is time between infection and detection of HIV antibody • ELISA, rapid test, Western blot indirectly diagnose HIV infection • PCR, p24 test directly for HIV itself • Best time to do HIV test: • 3 months after last risky exposure • when client is ready • 3 positive tests needed to confirm HIV

  26. Thank you! Questions?

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