Transcript Slide 1
Module 5
Supplemental Information
Laboratory Diagnostics,
Specimen Collection,
and Biosafety Issues
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Laboratory Diagnosis of
Avian Influenza
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Laboratory Diagnosis for
Avian Influenza
• Only test samples that were packed
during transport
• Only test samples with identification
information
• Use positive and negative controls for
all tests
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Laboratory Diagnosis for
Avian Influenza
Tests for respiratory samples:
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Virus isolation
PCR-based techniques
Immunofluorescence
Rapid antigen detection
Blood sera used for:
• Measurement of specific antibodies
• Viral isolation
• PCR-based techniques
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Virus Isolation
• Gold standard for detection of avian
influenza
• Allows identification of virus and test
for drug susceptibilities
• Technically difficult and requires BSL-3
laboratory
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PCR-based Techniques
• Examples: nested reverse transcriptase
polymerase chain reaction (RT-PCR)
and real-time RT-PCR
• Sensitivity depends on the particular
test, the influenza strain, and the type
of specimen used
– Sensitivity: 80 - 100%
– Specificity: 90 - 100%
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Immunofluorescence
• Works best on clinical specimens
collected immediately after symptoms
begin
• Results will tell you whether a
particular influenza virus is present
• Sensitivity and specificity not
established
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Indirect IF Staining of Cells From
Tracheal Aspirate
Anti-H5
Anti-H3
Anti-A/NP
Anti-B
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Taken from: World Bank Training by Alexander Klimov, CDC
Rapid Antigen Tests
• Detects influenza A and B virus
• Detects human strains of influenza
• Limitations:
– Not yet used to test for avian influenza
– Specificity and sensitivity not yet
established
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Serology Tests
• Used to confirm infection because it
takes several weeks to get results
• Useful when the sample is taken too
late for virus isolation
• Sensitivity and specificity of 80 - 100%
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Serology Tests
Types:
• Haemagglutination inhibition test
• Enzyme immunoassay
• Virus neutralization test
• Western Blot
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Serological Tests
Paired serum samples are most useful
Acute sample
Within 7 days after symptom onset
Convalescent sample
More than 12 days after symptom onset
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When Single Samples are
Appropriate
1. Convalescent samples collected in
outbreak investigations of novel
viruses (such as H7 or H9)
2. Single samples collected in
convalescent phase are compared to
age-matched controls
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Interpreting Serology Tests
Acute
Sample
low
low
high
Convalescent
Sample
Interpretation
low
No evidence of
Infection
high
Seroconversion
(evidence of infection)
high
Inconclusive; past
exposure to avian
influenza possible
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How to Avoid
Misinterpretations
• Use positive and negative controls
• Make sure you understand what the
test is identifying
• Use multiple tests to confirm results
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Laboratory Practice
Exercise
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References and Resources
• Recommended laboratory tests to identify avian influenza A
virus in specimens from humans. World Health Organization,
June, 2005.
http://www.who.int/csr/disease/avian_influenza/guidelines/avian
_labtests2.pdf
• WHO guidelines for the collection of human specimens for
laboratory diagnosis of avian influenza infection, 12 January
2005.
http://www.who.int/csr/disease/avian_influenza/guidelines/hum
anspecimens/en/index.html
• Infection control for viral haemorrhagic fevers in the African
health care setting. WHO/EMC/ESR/98.2 Section 6: Dispose of
Waste Safely
http://www.who.int/csr/resources/publications/ebola/WHO_EMC
_ESR_98_2_EN/en/index.html
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