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Instructions for users. This slide presentation provides an overview of the diagnostic and laboratory testing aspects of JE. Below many of the slides, there are notes to explain the information in the slide. You should adapt the presentation so it is relevant to your audience in your country.

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instructions for users
Instructions for users
  • This slide presentation provides an overview of the diagnostic and laboratory testing aspects of JE.
  • Below many of the slides, there are notes to explain the information in the slide.
  • You should adapt the presentation so it is relevant to your audience in your country.
  • This presentation is very long if used in total. Different sections could be presented by different presenters or in different sessions.
  • Provide examples of the actual materials (e.g., specimen tubes) and include practical sessions when possible. Suggestions are provided.
learning objectives
Learning Objectives

Participants will:

  • Understand how diagnostics can enhance surveillance for JE.
  • Review different tests that can be done to diagnose JE infection.
  • Revise principles of MAC ELISA testing.
  • Know types of specimens that can be tested.
  • Be familiar with the collection, storage and transport requirements for specimens.
why do we need diagnostics
Why do we need diagnostics?
  • JE surveillance is based on surveillance for cases of acute encephalitis syndrome (AES).
  • AES has
    • Many potential agents (e.g., JE, herpes simplex, Ebstein Barr viruses).
    • Several epidemic agents (e.g., JE, Enterovirus 71, Nipah viruses).
  • There are no specific signs or symptoms that distinguish JE from other causes of AES, so laboratory testing is needed to determine if JE is the cause of illness.
how can you use diagnostic information
How can you use diagnostic information?
  • Allows you to determine the proportion of all encephalitis (AES) cases that are due to JE.
    • e.g., to estimate the specific disease burden from JE
  • Allows you to determine if any of the encephalitis (AES) cases are due to JE.
    • e.g., is an outbreak of encephalitis due to JE or another agent?
different countries different stages different purposes 1
Different countries, different stages, different purposes (1)

No previous JE control (e.g., Cambodia)

  • Aim of surveillance
    • Determine disease burden from JE.
  • Strategy
    • Monitor AES cases nationwide.
    • Use diagnostics in certain sentinel sites.
    • Estimate proportion of all AES cases due to JE.
different countries different stages different purposes 2
Different countries, different stages, different purposes (2)

Introduced control program for JE (e.g., China)

  • Aim of surveillance
    • Monitor progress towards control of disease.
    • Identify at-risk areas and populations that require further interventions.
  • Strategy
    • Confirmatory test required for most cases.
laboratory criteria for diagnosis who surveillance guidelines for je
Laboratory criteria for diagnosis: WHO surveillance guidelines for JE

Laboratory confirmation of a JE virus infection includes:

  • Presence of JE virus-specific IgM antibody in a single sample of cerebrospinal fluid (CSF) or serum as detected by an IgM-capture ELISA specifically for JE virus;

OR

  • Detection of JE virus antigens in tissue by immunohistochemistry;

OR

  • Detection of JE virus genome in serum, plasma, blood, CSF, or tissue by reverse transcriptase PCR or an equally sensitive and specific nucleic acid amplification test;

OR

  • Isolation of JE virus in serum, plasma, blood, CSF, or tissue;

OR

  • A four-fold or greater rise in JE virus-specific antibody as measured by hemagglutination inhibition (HI) or plaque reduction neutralization assay (PRNT) in acute and convalescent-phase serum samples. The samples should be collected 14 days apart.
options for diagnostic tests in humans
Options for diagnostic tests in humans
  • Isolation, amplification, or antigen detection?
    • Viraemia in JE is low and short so the likelihood of a positive result is low.
    • High technology requirement and expensive.
  • Antibody-based (serology) methods?
    • High sensitivity (if properly timed samples).
    • Options include PRNT, ELISA, and HI.
antibody based serology methods
Antibody-based (serology) methods
  • Plaque reduction neutralization assay (PRNT)
    • Least cross-reactivity; most specific.
    • Up to 14 days to complete test.
    • Costly
    • High biosafety level requirements.
    • Early acute phase specimen less likely to test positive with PRNT than ELISA
    • Requires acute- & convalescent-phase serum.
  • Haemagglutination Inhibition (HI)
    • High levels of cross-reactivity with other flaviviruses, low specificity.
    • Anamnestic response with secondary flavivirus infection.
antibody based serology methods 2
Antibody-based (serology) methods (2)
  • JE-specific IgM capture ELISA
    • Advantages
      • Simple.
      • Sensitivity of IgM detection good as competition by IgG molecules eliminated.
    • Disadvantages
      • Some cross-reactivity with other flaviruses.

Summary: ELISA is most feasible testing methodology

slide12

Equipment for performing the ELISA test

Pipettes

Incubator

ELISA reader

slide14

Y

Y

Y

Y

Y

Reporter molecule

Y

Anti-EJEV Mab

*

Japanese encephalitis E protein

Sample containing human IgM

Y

Anti-human IgM

slide15

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

Y

*

*

*

*

Y

Y

Y

Y

Y

Y

Y

Y

type of specimens 1
Type of specimens (1)
  • CSF
    • Preferred sample whenever possible.
  • SERUM
    • Most common sample for testing.
type of specimens 2
Type of specimens (2)
  • Serum
    • Easy to collect.
    • A JE IgM positive result from the serum of a patient with encephalitis is a good indicator of acute infection (even though there is a problem of some cross-reactivity with other flaviviruses such as dengue virus).
type of specimens 3
Type of specimens (3)
  • CSF
    • The finding of JE IgM in CSF confirms the diagnosis of JE.
    • IgM to JE virus rises earlier in CSF than in serum and rises to higher levels in CSF than in serum (2 to 4 times)
    • Whenever possible when CSF is collected for management purposes, an additional tube should be collected for ELISA testing.
additional tests
Additional tests

Further confirmatory tests (testing for other flaviviruses that circulate in the area) should be carried out if:

  • There is circulation of dengue virus in addition to JE.
  • There is a suspected case in an area not having data supportive of JE transmission.
  • When JE vaccination coverage is very high.
timing of specimen collection
Timing of specimen collection
  • First specimens (blood and CSF) should be collected on admission to hospital or when patient first seen.
  • A follow up specimen (blood) should be collected at least 10 days after onset (or before discharge or death).
rationale for timing of specimen collection
Rationale for timing of specimen collection
  • IgM antibody levels rise steadily after onset of encephalitis.
  • The percentage of patients with IgM detectable in serum increases with days after onset.
study the kinetics of igm and igg
Study: the kinetics of IgM and IgG

On admission, only 53% of serum specimens and 68% CSF specimens were positive.

Kinetics of IgM and IgG responses to JE virus in human serum and cerebrospinal fluid. Burke DS, Nisalak A, Ussery MA et al

Journal of Infectious Diseases 1985. 151: 1093-1099

slide23

Therefore, it is important to collect a follow up blood specimen at least 10 days after onset (or approximately 7 days after admission) or before discharge or death.

slide25

Concentration

Concentration

Encephalitis onset

slide26

Day 4

- 6 illness

JE virus in blood

Concentration

Concentration

Infection

Encephalitis onset

Incubation: 5 - 15days

slide27

D4

D6 illness

D14

D21 illness

JEV - Blood

JEV - CNS & tissue

Concentration

Concentration

Infection

Encephalitis onset

Incubation: 5 - 15d

slide28

D4

D6 illness

D14

D21 illness

JEV - Blood

JEV - CNS & tissue

Serum & CSF IgM Ab

Concentration

Concentration

Infection

1Y after illness

Encephalitis onset

Incubation: 5 - 15d

slide29

D4

D6 illness

D14

D21 illness

JEV - Blood

JEV - CNS & tissue

Serum & CSF IgM Ab

IgG, HI & Neut Ab

Concentration

Concentration

Infection

1Y after illness

Encephalitis onset

Incubation: 5 - 15d

step 1 complete forms and specimen identification
Step 1: Complete forms and specimen identification
  • Fill in the information on tube (identifying information, date of collection, and other information as required).
  • Fill in the laboratory form that will accompany specimens.
collection and processing of serum
Collection and processing of serum
  • Collect blood in a tube that does not contain any chemicals or anticoagulants.
  • Collect 5mL of whole blood (for very small children collect 1mL).
  • Place tube upright for 30-60 minutes then when firm clot has formed, centrifuge tube for 20 minutes at 2500rpm.
  • Remove serum with a pipette and place in a plastic storage tube (2-3mL microtube or cryovial).
  • If 5mL of blood was collected it will result in about 2mL of serum.
collection of csf for je elisa testing
Collection of CSF for JE ELISA testing
  • Collect 2mL of cerebrospinal fluid into a sterile, plastic microtube or cryovial.
  • Place in the refrigerator or, if ELISA testing will not occur within 7 days, place immediately in the freezer.
principles of storage of serum and csf 1
Principles of storage of serum and CSF (1)
  • Both serum and CSF samples should be stored in microtubes or cryovials.
  • If a serum or CSF sample can be tested within 7 days, it should be refrigerated until tested (4°C).
  • If it will be tested after more than 7 days, it should be frozen (-20°C) (-70°C also acceptable for serum)
principles of storage of serum and csf 2
Principles of storage of serum and CSF (2)
  • Periodically check the temperature of the refrigerator.
  • There should be a constant electricity supply to the refrigerator and freezer; if possible, have generator back up.
  • If electricity fails for longer than 2 to 3 hours during the storage of samples, the date and length of time of the power failure should be recorded.
  • Do not use the refrigerator/freezer for storage of other goods such as food or drink.
principles of transport of serum and csf specimens
Principles of transport of serum and CSF specimens
  • The sample should be kept cold during transport and arrive at the testing lab cold (or frozen if it has been previously frozen).
  • The transport time should be kept to a minimum.
  • Ensure samples will arrive at the testing laboratory when a staff member can receive them and immediately put them into cold storage.
  • Ensure all forms with patient information are complete and sent with the specimen.
options for transport
Options for transport
  • Cold box with dry ice.
  • Container filled with liquid nitrogen.
  • Cold box with wet ice.
transport of serum and csf specimens
Transport of serum and CSF specimens
  • Tubes (with lids tightly closed) should be packed with absorbent material between tubes (e.g., cotton wool) in a sealed container (e.g., 250-500mL screw top plastic container or can)
  • These containers and the dry ice (or wet ice) are then packed in outer packaging.
  • If ice is used, the outer package must be leak-proof.
  • If dry ice is used, the outer package must permit the release of carbon dioxide gas.
rules to follow to avoid problems with specimen quality
Rules to follow to avoid problems with specimen quality
  • If a serum or cerebrospinal fluid sample is being stored frozen, keep it frozen until it is thawed for immediate testing. Repeated freezing and thawing will damage the antibody.
  • Do not keep serum and cerebrospinal fluid samples for JE testing in warm conditions (such as a warm room) for more than 2 to 3 hours.
commercial je diagnostics where are we now
Commercial JE diagnostics: Where are we now?
  • There are several commercial ELISA diagnostic kits that are being evaluated for sensitivity, specificity and usability.
  • The advantages of commercial ELISA kits include
    • No long blocking or incubation steps.
    • Shorter time to run tests (4 to 8 hours).
acknowledgements
Acknowledgements

Please include the following acknowledgement if you use this slide set:

This slide set was adapted from a slide set prepared by PATH’s Japanese Encephalitis Project.

For information: www.JEproject.org