HIV Diagnosis and Testing HAIVN Harvard Medical School

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: n Explain the importance of HIV voluntary counseling and testing (VCT) n Describe the “window period” n Outline the different tests used to diagnose HIV infection n Describe the Vietnam MOH testing strategy 2

What is VCT and Why is it Important?

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: Client acceptance Of serostatus Referrals to care and treatment services including ART Early management of OIs VCT Reduction in mother-to child transmission Referrals to social and peer support Preventive therapy and contraceptive advice Facilitation of Behavior change 5

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

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

Window Period (1) n n 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 8

Window Period (2) n n 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 9

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

Serologic Tests to Diagnose HIV Infection

Overview of HIV Testing Methods n Antibody tests • Rapid Test • ELISA • Western Blot n Direct HIV Tests • Polymerase Chain Reaction (PCR) • Demonstration of viral antigen (p 24 antigen) n Early Infant Diagnosis • Dry Blood Spot 12

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

HIV Antibody Tests (2) Rapid ELISA/Rapid EIA (“Rapid Tests”) n n n 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 14

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

Direct HIV Tests (1) Polymerase Chain Reaction (PCR) n n 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 16

Direct HIV Tests (2) n n Demonstration of viral antigen (p 24 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-p 24 antibodies 17

Dry Blood Spot (DBS) Test (1) n n 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. 18

Dry Blood Spot (DBS) Test (2) 19

Testing Strategies

MOH Testing Strategies Testing Strategy At blood banks Routine screening in high prevalence areas HIV diagnosis • Positive test with one of these tests: ELISA, SERODIA, RAPID TEST. • If one simple positive screening test: reject for blood transfusion • Two tests with different ELISA “format” • Positive result confirmed if both ELISAs tests positive. • Three tests with different ELISA “format” • Positive result confirmed if all 3 tests 21 positive

Interpretation of HIV Test (1) Adults and Children > 18 Months Test Result Initial antibody test shows nonreactive result Diagnosis Negative Sample shows reactive results Positive concordantly by 3 screening tests Sample shows discordant results by the three screening tests Indeterminate 22

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

Small Group Activity

Key Points n n “Window period” is time between infection and detection of HIV antibody ELISA, rapid test, Western blot indirectly diagnose HIV infection • PCR, p 24 test directly for HIV itself n Best time to do HIV test: • 3 months after last risky exposure • when client is ready n 3 positive tests needed to confirm HIV 25

Thank you! Questions?