Human Immunodeficiency Virus: Laboratory Diagnosis of (HIV)
Human Immunodeficiency Virus: Laboratory Diagnosis of (HIV)
Human Immunodeficiency Virus: Laboratory Diagnosis of (HIV)
(PCR)
(GAG)
Diagnostic lab test for HIV infection
A- Tests to diagnose HIV infections:
1- Screening 2- Confirmatory
B- Tests for follow up the disease:
1- Viral load by Quantitative PCR 2- Th-cells count (CD4+)
C- Tests for the complication of the disease:
1- TB infection 2- HBV
3- HCV 4- Toxoplasma
5- Liver function tests 6- UTIs
7- Others.
A- Tests to diagnose HIV infections
1- Screening tests
These test are rapid in giving results however, they are
not diagnostic and need confirmation by the confirmatory
tests
The Screening tests include:
i- ELISA tests (combined Ag-Ab Immunoassays) for
detecting HIV-1 & HIV-2 antibodies and P24 Ag of HIV-1.
or chemiluminescent immunoassay testing.
ii- Rapid tests
i- ELISA or chemiluminescent
immunoassay testing
Add Sample
Test Control
Conjugate line
Line
(WB)
(PCR)
REASONS FOR FALSE-POSITIVE, FALSE-NEGATIVE, AND
INDETERMINATE RESULTS IN ASSAYS FOR THE DETECTION OF
ANTIBODIES AGAINST HIV
Reasons for False- • Increased sensitivity of assays, leading to
Positive HIV reduced specificity
Screening Test • Technical errors
Results • Presence of HIV antibodies in recipients of HIV-1
trial vaccines.
Other rare possibilities:
• Hypergammaglobulinemia/antibodies reactive to
cellular components
• Influenza vaccination may cause cross-reactivity
with HIV antibody assays. The time course for such
cross-reactivity remains uncertain.
Reasons for False- • Testing individuals during the window period (the
Negative HIV incubation period between exposure and seroconversion)
• Technical errors
Screening Test
• HIV-2 (for tests designed to detect only HIV-1).
Results
Other rare possibilities:
• Delayed antibody synthesis in infants and persons
receiving post-exposure prophylaxis or with concurrent
acute hepatitis C infection
• Diminished immune response in individuals receiving
intensive or long-term immunosuppressive therapy
• Congenital or drug-induced hypogammaglobulinemia or
agammaglobulinemia
• Insufficient host antibody response (i.e., advanced HIV
disease)
• Unavailability of antibodies due to the formation of
antigen-antibody complexes
• Reduced sensitivity assays
Reasons for Probable True Positive (HIV Infection)
Indeterminate • Seroconverting
• HIV-2 infection
* Western Blot
• Technical errors
Results Probable True Negative (No HIV Infection)
• Recipients of HIV-1 trial vaccine
(positive • Antibodies reactive to cellular components, as in
screening and o Multiparous women
negative WB) o Polytransfused patients
o Patients receiving chronic hemodialysis
o Patients with autoimmune disease
• Recipients of influenza and hepatitis B virus vaccines
• Persons with non-HIV acute viral infections
• Congenital bleeding disorders
• Alcoholic hepatitis and other chronic liver diseases
• Hematologic malignancies, lymphomas
• Positive rapid plasma reagin test
• Technical errors
Other lab tests for HIV patients
References:
Centers for Disease Control and Prevention and Association of Public Health Laboratories. Laboratory Testing
for the Diagnosis of HIV Infection: Updated Recommendations. Available at
http://stacks.cdc.gov/view/cdc/23447. Published June 27, 2014. Accessed [30/11/2015].
Diagnosis of HIV-1 Infection. Estelle Piwowar-Manning, HPTN Central Laboratory. The Johns Hopkins
University.
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