HIV testing - INTRODUCTORY COURSE FOR NURSES

1. 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