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|
Prepared by Samuel Breit, Andrew Carr,
Tony Kelleher, Bill Sewell
| TEST |
INDICATION |
INTERPRETATION |
| HIV
Ab |
- Diagnosis of HIV infection
|
- Positive - diagnostic of HIV
infection
- Negative - excludes HIV infection
>/= 3 months duration
- Indeterminate - suggests
cross-reactivity, recent HIV infection or late stage HIV infection. Supplemental testing
(p24 antigen, HIV DNA) will be automatically performed to exclude HIV. Repeat testing is
usually recommended to completely exclude HIV.
- Recent risk exposure retested in 2-3
months, if negative. A person with a mononucleaosis illness with negative mono test should
have HIV Ab test which should be repeated in 2-4 weeks
|
| HIV
p24 Ag |
- Diagnosis of primary HIV infection
- Diagnosis of neonatal HIV infection
|
- Positive may be found in a high % of
those with acute HIV infection prior to seroconversion
- In neonate positive test highly
suggestive of infection.
|
| T-CELL
SUBSETS |
|
- Inverted CD4:CD8 consistent with HIV
infection.
- CD4 counts > 500 = minimal immune
damage.
- CD4 counts 200-500 = moderate imune
damage. Antiretroviral therapy usually indicated.
- CD4 counts <200 = severe immune
damage. Antiretroviral therapy and antimicrobial (especially PCP) prophylaxis required.
- Test should be repeated every 3-4 months
in asymptomatic persons. More frequently in symptomatic persons or those with evidence of
falling CD4 cell counts.
|
| HIV
RNA |
|
- Strong predictor of clinical progression
independent of CD4 count
- RNA may increase for up to 6 weeks post
infectious illness or vaccination.
- RNA > 10,000-30,000 copies/mL plasma;
antiretroviral generally recommended regardless of symptoms or CD4 count.
- Should be measured with CD4 count (every
3-4 months if stable, more often if treatment initiation or alteration required).
- Should NOT be used for diagnosis of HIV
infection. Results from different kit types and laboratories may not be well correlated
|
| HIV
DNA |
- Supplemental diagnostic test
|
- Detects HIV DNA within peripheral blood
cells
- Useful in resolving indeterminate
results, particularly primary/neonatal HIV infection, where it precedes presence of p24
antigen by a few days.
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