HIV - POCT testing Flashcards
How many types of HIV tests exist?
Two forms
What are both HIV tests based on?
Immunoassay
What are the two HIV tests that can be done?
A rapid finger-prick or mouth-swab POCT
A blood test requiring laboratory analysis
Where are HIV tests done?
Sexual health clinics
Genitourinary medicine clinics
Some GP surgeries
Clinics run by charities
Antenatal clinics
Private clinics
What are the two types of POCT tests?
3rd generation
4th generation
What does the 3rd generation test for?
Only HIV antibodies
What does the 4th generation test for?
HIV Ab and p24 antigen
Proteins on the envelope
Look for antigens before antibodies appear in the blood
What is the window period?
Gap in antibody testing
Time between a persion is infected with HIV until the point when a test can detect HIV
Why is the 4th generation test beneficial?
Reduces the window period of detecting HIV infection
What is the window period for detecting antibodies (3rd generation)?
Usually after 6 months but almost certainly by 3 months after exposure
What is the window period for detecting antigens (4th generation)?
14 - 21 days after exposure
What is done before testing for HIV?
Must be a pre-test discussion
Needs to establish consent for the HIV test
Explain
- what test will be given
- how long the result will take to come back
- how the result will be given to the patient
Confidential
Explain the benefits of knowing one’s HIV status and treatment possibilities
What are the benefits of knowing the HIV status of a person?
Won’t spread to partner
The sooner diagnosed, the sooner can start getting treated
Implement a more healthy lifestyle
What type of test is a POCT test?
Immunochromatographic lateral-flow assay
What type of sample is needed for a POCT?
Finger prick
Mouth swab
When do results of POCT come back?
POCT can produce results in minutes
20-30 minutes for a finger prick test
What are the disadvantages of HIV POCT tests?
Reduced specificity and sensitivity
What is the next steps when POCT tests come back positive?
Confirmed by a blood test
What needs to be done if someone has been exposed to HIV in the last 3 months?
Needs to come to lab at 3 month period after exposure to take test again
Do laboratory test to investigate using 4th generation testing
How is a HIV POCT Immunochromatographic lateral flow assay carried out?
Place blood from finger prick on the sample pad
Gold microparticle coated in HIV antigen placed on the sample pad
Nitrocellulose membrane contains HIV antigens which capture the gold microparticle immune complexes
Captured gold microparticles forms a red line when HIV atinbodies are present in the patient’s sample
Absorbant pad draws the sample across the reaction membrane
What ensures that the POCT test was carried out correctly?
Control line
Shows assay worked properly
How is the POCT 3rd and 4th generation tests confirmed?
Blood sample taken by venepuncture in the Virology department laboratory
What is the average time for blood results to come back?
2-3 days
Can be fast-tracked to a matter of hours
Which schemes have made it easier to test for HIV?
Increase the turn around for POCT tests
Outreach programmes
Walk in centers
Drop-in clinics
How do drop-in clinics increase HIV testing?
No appointment needed
Convenient
Anonymous
Perceived as being friendly and non-judgemental
Non-invasive test
Fast results
Clinics sited in and targeted at high-risk communities
What are the next steps one a POCT comes back positive or HIV?
HIV to be staged
Antiviral therapy commences
Prophylaxis against possible opportunistic infections if appropriate
