Symptom To Diagnosis - AIDS Flashcards
HIV - common modes of transmission:
62% –> male to male sexual transmission.
17% –> needle sharing among injection drug users.
13% –> heterosexual transmission.
+ vertical transmission from mother to child.
Current risk associated with blood transfusion for HIV 1 and 2:
1/1.800.000
The highest risk of sexual transmission is among patients with:
- Unprotected receptive anal intercourse.
- Sex for hire workers.
- Sexual contacts of sex for hire workers.
- Individuals with multiple sexual partners.
CD4 count in chronic HIV infection:
There is a very slowly progressive disease in the CD4 T cell count in the blood –> 2 BILLION cells destroyed every and replaced every day.
BOTH infected and NONinfected CD4 T cells are activated and destroyed.
Stages of HIV infection:
- Viral transmission.
- Primary infection.
- Seroconversion.
- Clinically latent period.
- Early symptomatic HIV infection.
- AIDS and advanced HIV infection.
Similar to any other diagnosis, the PPV in HIV diagnosis is determined by?
3 factors:
- Pretest probability.
- Sensitivity.
- Specificity.
Estimating pretest probability in HIV infection:
- Risk factors: MSM, injection drug abuse, multiple sexual partners.
- Prevalence of HIV infection - Varies from 0.3% in the US to >50% in certain high risk groups.
False(+) results in HIV EIA testing:
- Recent influenza.
- Hep B immunization.
- DNA virus infection.
- Increasing parity.
- PRP (+).
- Improper heating.
- Clerical error.
- HIV vaccine.
- Cross reacting antibody.
False (-) results in HIV EIA testing:
- Recent HIV infection prior to development of antibodies (window period) - Seroconversion occurs sometime between 10days to 6 weeks.
- Rare causes –> Advanced AIDS with swro-REVERSION, immunosuppression therapy, malignancy, bone marrow transplant, B cell dysfunction, replacement transfusion, hypogammaglobulinemia, infection by rare HIV types.
Western blot testing for HIV - Positive results require:
At least 2 of the following 3 bands:
- gp160/120.
- gp41.
- p24.
Western blot testing for HIV - Negative results require:
The ABSENCE OF ANY visible bands.
Indeterminate results in HIV diagnosis:
Occurs in 10-15% of cases.
3 pivotal considerations help frame the DDX:
- Acuity of symptoms.
- Degree of immunosuppression.
- Mass lesion on neuroimaging.
DDx of headache in patient with HIV - Meningoencephalitis:
- Cryptococcal meningitis.
- HIV encephalopathy.
- CMV ventriculoencephalitis.
- TB meningoencephalitis.
- Neurosyphilis.
- Coccidioidomycosis. (Southwestern)
DDx of headache in patient with HIV - Mass lesions:
- Toxoplasmosis.
- PML.
- Primary cns lymphoma.
- Rare pathogens/presentations - Cryptocomma, tuberculoma, Nocardia, Aspergillus, bacterial abscess.
Cryptococcal meningoencephalitis - Textbook presentation:
Patients typically have a subacute headache, malaise, and fever thta develop over days to weeks. Mental status changes may be seen.
Importantly, meningismus is often ABSENT due to the host’s inability to mount an inflammatory reaction.
MCC of meningoencephalitis in HIV(+):
Cryptococcal meningitis.
Transmission of cryptococcal meningoencephalitis:
Encapsulated fungus acquired via inhalation.
Cryptococcal meningoencephalitis - CD4 count:
<100.
Increased intracranial pressure in cryptococcal meningoencephalitis:
It is common (>20cmH2O in lateral decubitus position) - 70% of patients.
Cryptococcal meningoencephalitis - Mortality:
6-12%.
Pulmonary involvement in cryptococcal meningitis:
6-23%.
Cryptococcal meningitis - History:
65-95% - Fever.
73-100% - Headache.
Median duration of symptoms: 31 days (1-120days).
Cryptococcal meningitis - Physical exam:
22-27% - Stiff neck. 18-22% - Photophobia. 22% - Mental status change. 10% - Focal Neurologic signs or seizures. 14% - NO CNS signs or symptoms.
Bottom line about clinical manifestations of cryptococcal meningitis:
- Often indolent - Small percentage exhibit meningismus or photophobia.
- Some patients have only fever and malaise.
Cryptococcal meningitis - Blood cultures positive?
15-35%.