HIV diagnosis
(general)
Immunoassays
NAT (PCR)
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HIV diagnosis (general)
• Serologic tests for HIV infection are based
upon detection of IgG antibodies against HIV-1
antigens in serum
HIV diagnosis (general)
• Yes but not only IgG
HIV diagnosis (general)
• HIV-specific IgG antibodies appear 6 to 12
weeks following HIV infection in the majority
of patients
HIV diagnosis (general)
• Yes
HIV diagnosis (general)
• HIV-specific IgG antibodies appear by six
months in all HIV infected patients
HIV diagnosis (general)
• HIV-specific IgG antibodies appear by six
months in 95 percent of patients
HIV diagnosis (general)
• Name 2 of the most specific tests to diagnose
HIV
HIV diagnosis (general)
• Viral culture
• NAT (PCR)
HIV diagnosis (general)
• Explain the difference between an HIV EIA test
and an HIV ELISA test
HIV diagnosis (general)
• EIA: conjugated HIV antigens on the plate 
not “sandwich method”; 3rd and 4th
generation are “sandwich methods”;
Immunoassays-10
• The standard screening assay for detecting
antibodies to HIV is an enzyme immunoassay
(EIA). A confirmatory Western blot is
performed if the screening test is positive to
exclude a false positive test.
Immunoassays-10
• Yes
Immunoassays-20
• The most common cause of a false negative
HIV antibody test in a high-risk patient is that
the assay is being conducted during the
"window period" of acute HIV infection prior
to seroconversion
Immunoassays-20
• Yes
Immunoassays - 30
• False negative HIV antibody tests have been
reported among participants in HIV vaccine
trials
Immunoassays - 30
• False: Positive HIV antibody tests have been
reported among participants in HIV vaccine
trials.
Immunoassays - 40
• An AA patient from Cameroon presents with
acute febrile illness, skin rash and
lymphadenopathy 3 weeks after a high risk
exposure. What tests should you order?
Immunoassays - 40
• At least second generation immunoassay and
also NAT testing for HIV-2
Immunoassays - 50
• The patient with an indeterminate result with
an HIV rapid test should have repeat testing in
one to two months with
a) rapid serologies
b) Standard serologies
c) Rapid OR standard serologies
Immunoassays - 50
• C: The patient with an indeterminate result
should have repeat testing in one to two
months with rapid or standard serologies PLUS
viral NAT
NAT (PCR)- 10
• The major limitations of these assays include
cost, the requirement for venipuncture, and
time interval between sample collection and
test results
NAT (PCR)- 10
• Correct
NAT (PCR)- 20
• The viral NAT should always be used to
diagnose acute HIV infection
NAT (PCR)- 20
• Only if there is clinical suspicion
NAT (PCR)- 30
• Quantitative HIV RNA is the preferred test for
staging and therapeutic monitoring
NAT (PCR)- 30
• Correct
NAT (PCR)- 40
• A HIV-infected mother on ART delivers a baby.
Which test will best rule out HIV infection in
the baby?
• A) RNA qual PCR
• B) DNA PCR
• C) 4th generation immunoassays
• D) Neither of the above. The baby will need
long term follow up with serial tests
NAT (PCR)- 40
• B
NAT (PCR)- 50
• An AA patient from Cameroon presents with acute
febrile illness, skin rash and lymphadenopathy 3
weeks after a high risk exposure. What tests
should you order?
• a) 4th or 3rd generation immunoassay
• b) a + standard HIV PCR available in the clinical lab
• C) a+ contact reference lab for appropriate PCR
testing
• D) None of the standard tests will rule out
completely the possibility of HIV infection
NAT (PCR)- 50
• D