HIV monitoring Flashcards
Why is it important to understand the natural history of HIV infection:
To understand the determination for the need of antiretroviral therapy
What happens to viral load and CD4 count with time:
Some progress quick - go from primary infection to opportunistic infection
Some show little progression over many years
What happens within the first few wees of infection
Falling CD4 count with big rise in viral load
This recovers within 3-4 months
What happens in the longer term progression of HIV infection?
More progressive loss of CD4
When are constitutional symptoms of HIV observed?
CD4 count decreases beyond 350
At which CD4 count are opportunistic diseases seen?
Between 250-300 CD4 count
What is the definition of viral load?
Amount of HIV RNA in peripheral blood
What is the commonest assay used to measure HIV viral load?
RT-PCR
What sample is required to test for viral load?
Whole blood
Plasma
What are the three different assays used to measure the amount of genetic material?
Reverse transcription by polymerase chain reaction
bDNA and NASBA
Real-time PCR
Describe reverse transcription by polymerase chain reaction
Viral RNA is transcribed into DNA
Millions of copies are amplified using standard PCR
Describe NASBA and bDNA
Branched DNA test
Uses nucleic acid hybridization to detect the target
Doesn’t rely on PCR
Describe the process of reverse transcription
- Using reverse transcriptase polymeraser the RNA is turned into clone DNA
- Replicated in terms of polymerase chain reactions
- More and more copies of the cDNA made
- Detect the number of copies made by the number of biotin related primers
How are biotin related primers used to measure the amount of DNA?
Emit colour
Light measure in machine
Why is bDNA and NASBA used?
More quantitative
