Module 5 Supplemental Information

1
Module 5Supplemental 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
• 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
Taken from World Bank Training by Alexander
Klimov, CDC
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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)
• Single samples collected in convalescent phase
  are compared to age-matched controls

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Interpreting Serology Tests
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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/gui
  delines/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/gui
  delines/humanspecimens/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/publicatio
  ns/ebola/WHO_EMC_ESR_98_2_EN/en/index.html