Ppt2.hiv testing technologies
- 2. HIV TESTING TECHNOLOGIES Highly sensitive, specific, simple-to-use, rapid antibody tests that do not require sophisticated laboratory services, running water or electricity is an important advance Testing can occur outside laboratory settings, does not require specialized equipment and can be carried out in primary health facilities by appropriately trained non- laboratory personnel, including counselors
- 3. Overview of HIV Testing HIV tests detect antibodies or antigens associated with HIV in whole blood, saliva, or urine Blood sampling is the most common method of testing HIV tests are very accurate
- 4. Types of HIV tests 1. Antibody test ELISA Western Blot Rapid tests 1. Antigen test(HIV Viral Tests) p24 antigen test PCR (polymerase chain reaction) tests DNA.RNA PCR
- 5. Antibody testsAntibody tests After infection with HIV, the body makes antibodies to fight the virus It may take 4 to 6 weeks, but occasionally up to 3 months for antibodies to become detectable in the blood Rapid HIV tests and the ELISA are the most common antibody tests
- 6. ELISAELISA 99.5% sensitive, standard screening test Identifies antibodies to HIV infected pt. Highly sensitive but not always specific. Accurate only in pt over 18 month of age Does not detect “window period” Designed for large number of patients Is not cost effective b/se all positive result should be confirmed by additional tests?
- 7. Limitations of the ELISA:Limitations of the ELISA: Tests must be done in batches of 40−90 Positive results must be confirmed with another ELISA or Western blot Specimens sent to a laboratory for testing— results may take days to weeks Test requires refrigeration and specific reagents
- 8. Western BlotWestern Blot Detects bands of protein specific to HIV antibody Negative in the absence of protein band Positive with the presence of protein band Confirmatory test.
- 9. Several rapid test detects HIV Anti body They share characteristics of ELISA Most of them are 99-100% sensitive and specific Specimen saliva, urine or blood Determine KHB (screening test) Capillus stat –pack test (confirmatory) Uni-Gold or serocard Tie breaker Rapid tests
- 10. Accurate results within 20-40 minutes Can be done in the clinic setting No batching required Limitation- under 18 month & window period HCWs can be trained to perform the tests Usually do not require special equipment, electricity or refrigeration Rapid tests cont’d
- 11. Benefits of rapid HIV testing includeBenefits of rapid HIV testing include On-site testing and same day results Lower risk of administrative error Accepted by clients Fewer resources required: Human resources Resources at the facility Financial resources Lower risk of occupational exposure
- 12. Rapid HIV Testing AlgorithmsRapid HIV Testing Algorithms 1. Serial testing 2. Parallel testing
- 13. Serial testingSerial testing Blood sample taken and tested once If first test result is non-reactive, result is given to client as HIV-negative If first test result is reactive, blood sample is tested again using different brand of rapid test ¨ If second test is reactive, result is reported as HIV-positive ¨ If second test is negative, a third test known as a “tiebreaker” is performed
- 14. 14 Algorithm for Use of 3 Rapid Tests in Testing and Counseling Services Pre-Test Education and/or Counseling First HIV Rapid Test Positive Test Result Negative test result/ Counsel for Negative Results Second HIV rapid Test Positive Test Result/Counsel for Positive Results Negative Test Result Third HIV Rapid Test Negative Test Result/ Counsel for Negative Test Result Positive Test Result/Counsel for Positive Test Result First HIV Rapid Test Positive Test Result Negative test result/ Counsel for Negative Results Positive Test Result/Counsel for Positive Results Negative Test Result Third HIV Rapid Test Negative Test Result/ Counsel for Negative Test Result Positive Test Result/Counsel for Positive Test Result
- 15. Rapid HIV Testing (Serial testing) Rapid HIV Testing (Serial testing) First TestFirst Test PositivePositive Negative Counsel for Negative Result Negative Counsel for Negative Result Second TestSecond Test NegativeNegativePositive Counsel for Positive Result Positive Counsel for Positive Result Tie-breaker TestTie-breaker Test Positive Counsel for Positive Result Positive Counsel for Positive Result Negative Counsel for Negative Result Negative Counsel for Negative Result
- 16. Two HIV tests are performed on same sample at the same time, e.g., in parallel If both are non-reactive, client reported HIV-negative If both are reactive, client reported HIV- positive If one is reactive and the other non-reactive, a “tiebreaker test” is performed Parallel testingParallel testing
- 17. Rapid HIV Testing (Parallel Testing) Rapid HIV Testing (Parallel Testing) Both Tests Positive Counsel for Positive Result Both Tests Positive Counsel for Positive Result Both Tests Negative Counsel for Negative Result Both Tests Negative Counsel for Negative Result Tie-breaker TestTie-breaker Test Positive Counsel for Positive Result Positive Counsel for Positive Result Negative Counsel for Negative Result Negative Counsel for Negative Result First AND Second TestFirst AND Second Test DiscordantDiscordant
- 18. Interpreting HIV Antibody TestsInterpreting HIV Antibody Tests A positive HIV test Means that antibodies to HIV are present. It does not mean that the client has AIDS A negative HIV test : The person is not infected with HIV, or The person is infected with the virus but is in the window period A negative test does not mean that person cannot become infected. There is no such thing as immunity to HIV infection
- 19. Antigen test( HIV Viral Tests)Antigen test( HIV Viral Tests) Viral tests detect the presence of HIV in blood Viral tests must be done by trained personnel in the laboratory
- 20. p24 antigen testp24 antigen test Measures one of the HIV proteins used for screening blood Infant diagnosis
- 21. PCR (polymerase chain reaction) testsPCR (polymerase chain reaction) tests DNA.RNA PCR Highly sensitive and specific for HIV Used when the result of diagnostic tests are unclear Antigen testing Most commonly utilized to diagnose HIV infection in children <18 month RNA PCR detects and measures amount of virus in blood (viral load)
- 22. Five Steps to HIV TestingFive Steps to HIV Testing 1. A specimen is obtained 2. The specimen is processed 3. Test is conducted by a HCW or laboratory technician 4. The client is told their result 5. HCW provides post-test counselling, support and appropriate referrals
- 23. Testing Procedure for HIV InfectionTesting Procedure for HIV Infection Infection control and Standard Precautions Proper labelling Proper specimen collection procedures Required volume per test Proper reagents per test Correct timing per test Interpretation of results Proper record-keeping Proper disposal procedures Observe these points:
- 24. Testing Procedure for HIV Infection (Continued)Testing Procedure for HIV Infection (Continued) Factors affecting test performance: Storage and handling of test kits Changes in the environment Accuracy of equipment; external and internal controls Shelf-life of the chemicals for the tests (reagents) Technique for sample collection Quality of sample Use of equipment
- 25. Monitoring Progress in implementation Assess effectiveness and impact (+ and -) Access to testing and counselling, knowledge of serostatus Uptake of prevention, treatment, care and support services Mortality and morbidity HIV awareness and treatment literacy Social impact (e.g. rates of disclosure, discrimination, adverse outcomes) Cost effectiveness, Quality of lab services Reasons why PITC is performed