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Understanding HIV Testing & Counseling: Key Principles & Strategies for Effective Diagnosis

This session explores the importance of voluntary HIV testing and counseling, various diagnostic testing methods, and Vietnam's Ministry of Health testing strategy. It covers key principles, barriers to testing, different testing strategies, interpretation of results, diagnostic criteria for infants, and strategies for confirmation of HIV infection.

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Understanding HIV Testing & Counseling: Key Principles & Strategies for Effective Diagnosis

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

  2. Learning Objectives By the end of this session, participants will be able to: • Explain the importance of HIV voluntary counseling and testing (VCT) • List at least 3 HIV diagnostic testing • Describe the Vietnam MOH testing strategy

  3. 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

  4. Why is VCT Important ? VCT serves as an entry point for:

  5. VCT for Special Populations

  6. What are the Barriers to VCT?

  7. 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

  8. HIV Testing

  9. 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

  10. Serologic Tests to Diagnose HIV Infection

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

  12. 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

  13. 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

  14. 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

  15. 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

  16. 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.

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

  18. Testing Strategies

  19. MOH Testing Strategies(1) Strategy I: At blood banks • Positive test with one of these tests: ELISA, SERODIA, RAPID TEST. • If one simple positive screening test: reject for blood transfusion

  20. MOH Testing Strategies (2) Strategy II: Routine screening in high prevalence areas • Two tests with different ELISA “format” • Positive result confirmed if both ELISAs tests positive.

  21. MOH Testing Strategies (3) Strategy III: HIV diagnosis • Three tests with different ELISA “format” • Positive result confirmed if all 3 tests positive

  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. Diagnosis of severe HIV / AIDS in infants <18 months • Positive result for HIV antibodies testing • One symptoms of clinical stage 4 • At least 2 of the 3 following symptoms: • Oral thrush (in > one month old child) • Severe pneumonia • Severe infections • Other factors: • Mother died of HIV-related disease • Mother has HIV/AIDS progression • CD4 percentage <20%

  25. Key Points • HIV testing perform in any medical facility must be: • Voluntary and confidential • Including counseling before and after testing • Diagnosis of HIV is detected indirectly through the demonstration of virus-specific antibody: ELISA, rapid test, Western blot. • 3 positive tests needed to confirm HIV(Strategy III)

  26. Thank you! Question?

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