0527 - Immunological and Clinical Aspects of HIV Flashcards
What is the current epidemiology of HIV in Australia?
Around 27,000 cases. 1,250 new cases/year and rising. Prevalence increasing due to new cases and people living longer with disease.
What is epidemiology of HIV in the ACT?
ACT around 25 new cases/year. 38% of new diagnoses were acquired in last 12 months (almost all in MSM). Shows prevention isn’t working much at the moment. 31% are late diagnosis (CD4 less than 350).
What is the basis of the Government, clinical, and community response to HIV?
Focus on test more, treat early, and stay safe. Major biomedical approaches in addition to condoms.
Outline PrEP and PEP for HIV prevention.
Truvada
PrEP (Pre-exposure prophylaxis) - taken by high-risk people on a daily basis to reduce chance of acquiring HIV, but not on PBS or on TGA for prevention (only treatment). Legal to prescribe and import for personal use.
PEP (Post-exposure prophylaxis) - Truvada with or without 3rd drug for 4 weeks after exposure, within 72 hours but SOONER IS BETTER. No or minimal cost to patient.
Outline TasP and MTCT for HIV prevention
TasP (Treatment-as Prevention) - Treating to viral load below detectable appears to prevent transmission.
MTCT - Look after mum and baby will be OK, including no breastfeeding in developed world (not in developing world).
What are the necessary requirements for HIV testing?
Know risk factors for pre-test probability
Informed consent
Accurate identifiers
Know window periods and last exposure to ensure accurate test.
Remember to do a confirmatory test.
How does HIV testing by antigen/antibody assay work?
Combines P24 antigen and antibody assay - looks for both. Allows earlier pickup, by detecting the antigen potentially before antibodies have been created.
Antigen levels lower again quite quickly, but Ig’s stay up. This gives you best of both worlds - early pickup (DNA and P24 earlier, but need reference lab), and longer-term sensitivity.
Why is confirmatory testing important in HIV?
Screening test can lead to cross-reactivity from antibodies to other viral particles causing a false positive. Western Blot is used to confirm antibodies to a number of HIV-related proteins and give a definitive diagnosis (done in a reference lab).
Outline rapid tests for HIV testing.
Rapid tests - not as good as assays/Western Blot, but cost $20 and only take 20 minutes. Risk of false positives, but may encourage more at-risk individuals to test more often than they otherwise would.
Explain use of combination therapy in relation to HIV viral life cycle.
Drugs are enzyme inhibitors - Reverse transcriptase, integrase, and protease. Aim for one tablet, once a day (2-3 drug combination to prevent mutations), unless resistance is present. Just understand that some people are on different regimens, and will need to look them up for correct documentation.
Prevents viral replication, minimise risk of resistance, and allow CD4 recovery.
How can HIV be monitored over time?
CD4 count, but can’t use single T-cell measure, they fluctuate over time. Need to look at the pattern over time.
Once on treatment, look at viral load to monitor - aim is to get to undetectable level. Always treat if CD4 count is less than 350.
