HIV - testing

Question 1

DETECTION OF HIV INFECTION - HIV P24 PROT ELISA

i) what does this detect?
ii) what is coated on 96 well plate?
iii) what is added after the sample has been added?
iv) what can be added to allow visualisation?
v) what is the intensity of the colour proportional to?

Answer 1

i) detects HIB in the blood post infection
ii) anti HIV P24 antibody on 96 well plate
iii) add biointenylated anti virus HIV P24 antibody
iv) add horseradish peroxidase conj to spreavidin to visualise
v) intensity of colour is proportional to amount of P24 protein bound

Question 2

COMBINED HIV ANTIBODY + ELISA

i) what two things do they detect?
ii) what do third generation assays detected?

Answer 2

i) fourth gen assay that det p24 HIV protein antien as well as convential HIV antibodies
ii) third gen assays only detect HIV antibodies

Question 3

WHEN TO TEST

i) what is the eclipse period? can HIV be tested for in this period?
ii) what is the window period?
iii) from what day post infection will a 3rd gen antibody test detect HIV? 4th gen?

Answer 3

i) eclipse period is the time between the infection and when the virus RNA becomes detectable in blood
- cant test in this period

ii) window period is 45 days - time between exposure and when a fourth gen test will identify >99% infections

iii) 3rd gen will detect from 24 days
4th gen will detect from 15 days

Question 4

WHO SHOULD BE TESTED?

i) if a person identifies a exposure/risk less than 4 weeks previous - should they still be tested?
ii) what test should be offered? after how many days should the test be repeated?
iii) what test can be done if exposure was very recent?
iv) which test after how many days coming back negative is highly likely to exclude HIV infection?
v) after how many weeks would a further test be done if patient is deemed to be high risk?
vi) what should be done if test comes back positive?

Answer 4

i) yes - never turn someone away for a test

ii) offer a fourth gen test
- repeat after 45 days

iii) recent exposure > do a PCR resr
iv) fourth gen coming back after 45 days neg
v) do another test 8 weeks later if there is high risk but other tests were negative
vi) if test is positive then test the same materal again using a different rest, if that is positive then test an additional sample

Question 5

POINT OF CARE SELF TESTING

i) what do they usually detect?
ii) can they replace fourth gen tests?

Answer 5

i) HIV antibodies
ii) no cant replace fourth gen tests