HIV Flashcards
Physiology
HIV is an RNA retrovirus. HIV-1 is the most common type. HIV-2 is rare outside West Africa.
The virus enters and destroys the CD4 T helper cells.
An initial seroconversion flu-like illness occurs within a few weeks of infection. The infection is then asymptomatic until it progresses and the patient becomes immunocompromised and develops AIDS-defining illnesses and opportunistic infections potentially years later.
Transmission
HIV can’t spread through normal day to day activities including kissing. It is spread through:
Unprotected anal, vaginal or oral sexual activity.
Mother to child at any stage of pregnancy, birth or breastfeeding. This is referred to as vertical transmission.
Mucous membrane, blood or open wound exposure to infected blood or bodily fluids such as through sharing needles, needle-stick injuries or blood splashed in an eye.
AIDS Defining Illness
There is a long list of AIDS-defining illnesses associated with end-stage HIV infection where the CD4 count has dropped to a level that allows for unusual opportunistic infections and malignancies to appear. Some examples are:
Kaposi’s sarcoma
Pneumocystis jirovecii pneumonia (PCP)
Cytomegalovirus infection
Candidiasis (oesophageal or bronchial)
Lymphomas
Tuberculosis
Screen
HIV is a treatable condition and most patients are fit and healthy on treatment. There are many people that have HIV that do not know the diagnosis and these patients are at risk of the complications and spreading the disease. Generally the earlier a patient is diagnosed the better the outcome.
We should test practically everyone admitted to hospital with an infectious disease regardless of their risk factors. Patients with any risk factors should be tested. Antibody tests can be negative for 3 months following exposure so repeat testing is necessary if an initial test is negative within 3 months of a potential exposure.
Patients need to give consent for a test. Verbal consent should be documented prior to a test. Consent only needs to be as simple as “are you happy for us to test you for HIV?” Patients no longer require formal counselling or education prior to a test.
Testing
Antibody blood test. This is the typical test used in hospitals to screen for HIV. There is an option for patients to self sample by requesting a kit online and posting a sample of their blood to get tested for the antibody.
Testing for the p24 antigen, checking directly for this specific HIV antigen in the blood. This can give a positive result earlier in the infection compared with the antibody test.
PCR testing for the HIV RNA levels tests directly for the quantity of the HIV virus in the blood and gives a viral load.
Monitoring
CD4 count
This is a count of the number of CD4 cells in the blood. These are the cells destroyed by the HIV virus. The lower the count the higher the risk of opportunistic infection.
500-1200 cells/mm3 is the normal range
Under 200 cells/mm3 is considered end stage HIV / AIDS and puts the patient at high risk of opportunistic infections
Viral Load (VL)
Viral load is the number of copies of HIV RNA per ml of blood. “Undetectable” refers to a viral load below the labs recordable range (usually 50 – 100 copies/ml). The viral load can be in the hundreds of thousands in untreated HIV.
Treatment
Treatment should be coordinated by specialist HIV or GUM centres. It revolves around a combination of antiretroviral therapy (ART) medications. ART is offered to everyone with a diagnosis of HIV irrespective of viral load or CD4 count. Some regimes involve only a single combination tablet once per day that has the potential to completely suppress the infection. Specialist blood tests can establish the resistance of each HIV strain to different medications to help tailor treatment.
BHIVA guidelines (2015) recommend a starting regime of 2 NRTIs (e.g. tenofovir and emtricitabine) plus a third agent.
The aim of treatment is to achieve a normal CD4 count and undetectable viral load. As a general rule when a patient has normal CD4 and undetectable VL on ART treat their physical health problems (e.g. routine chest infections) as you would an HIV -ve patient. When prescribing be aware and check interactions any medication might have with the HIV therapy.
Highly Active Anti-Retrovirus Therapy (HAART) Medication Classes
Protease Inhibitors (PIs)
Integrase Inhibitors (IIs)
Nucleoside Reverse Transcriptase Inhibitors (NRTIs)
Non-Nucleoside Reverse Transcriptase Inhibitors (NNRTIs)
Entry Inhibitors (EIs)
Additional Management
Prophylactic co-trimoxazole (Septrin) is given to patients with CD4 < 200/mm3 to protect against pneumocystis jirovecii pneumonia (PCP).
HIV infection increases the risk of developing cardiovascular disease. Patients with HIV have close monitoring of cardiovascular risk factors and blood lipids and appropriate treatment (such as statins) to reduce their risk of developing cardiovascular disease.
Yearly cervical smears are required for women. HIV predisposes to developing cervical human papillomavirus (HPV) infection and cervical cancer so female patients need close monitoring to ensure early detection of these complications.
Vaccinations should be up to date including annual influenza, pneumococcal (every 5-10 years), hepatitis A and B, tetanus, diphtheria and polio. Patients should avoid live vaccines.
Reproductive Health
Reproductive Health
Advise condoms for vaginal and anal sex and dams for oral sex even with when both partners are positive. If the viral load is undetectable then transmission through unprotected sex is unheard of in large studies but not impossible. Partners should have regular HIV tests.
Where the affected partner has an undetectable viral load unprotected sex and pregnancy may be considered. It is also possible to conceive safely through techniques like sperm washing and IVF. Caesarean section should be used unless the mother has an undetectable viral load. Vaginal birth may be considered where the viral load is undetectable. Newborns to HIV positive mothers should receive ART for 4 weeks after birth to reduce the risk of vertical transmission.
Breastfeeding is only considered where the viral load is undetectable however there may still be a risk of contracting HIV through breastfeeding.
Post Exposure Prophylaxis
Post exposure prophylaxis can be used after exposure to HIV to reduce the risk of transmission. It is not 100% effective and must be commenced within a short period (less than 72 hours). The sooner it is started the better. A risk assessment about the probability of developing HIV should be balanced against the side effects of post exposure prophylaxis.
It involves a combination of ART therapy. The current regime is Truvada (emtricitabine / tenofovir) and raltegravir for 28 days.
HIV tests should be done initially but also a minimum of 3 months after exposure to confirm a negative status. Individuals should abstain from unprotected activity for a minimum of 3 months until confirmed negative.
