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
Why is CD4 count important in assessing HIV infection?
CD4 count is crucial for getting an idea of
- how the infection is progressing
- how treatment is working
Gives idea about the amount of immunosuppression
What sample is needed to measure the CD4 T cell count?
Whole blood
How is the assay performed to test for CD4 T cell count?
Sample is mixed with tagged anti-CD4 antibodies
Antibodies bind to CD4+ cells
Machine counts as the sample flows by the detector
How often are CD4 count tests done on HIV patients?
3-4 times a year
Gives an idea of progression of CD4 lymphopenia
Looks at the recovery of the immune system
What is a non-progressor?
Patients who show slow progression of the disease with time
What are the two main causes of action when treating HIV patients?
Deciding antiretroviral therapy
Prophylaxis against opportunistic infections
What two factors are crucial in determining course of action in HIV treatment?
CD4+
Viral load
What other tests are used to monitor HIV patients?
Full blood count
Serum biochemistry
Baseline serologies
Chest X-ray
Sexually Transmitted Infection screen
Anal cytology
Cervical cytology
What baseline serologies are often asked for in HIV patients?
CMV
HBV
HCV
Toxoplasma
How do you prevent co-infections in HIV patients?
Vaccinate against viruses
What is the risk associated with HIV patient and CMV/Toxoplasma?
Risk of reactivating
Why are CXRs ordered in HIV patients?
Standard of care
Know what normal chest looks like and if changes with time
What sexually transmitted infections are screened for?
Syphilis
Gonorrhea
Chlamydia
Which patients undergo anal cytology?
Men who have sex with men
Why are cervical cytologies asked for in HIV patients?
Increased risk of CIN and cervical cancer in HIV+ women
Why are CD4+ counts and viral load regularly monitored?
Determine when to intervene with antivirals
Prophylaxis against opportunistic infections
