Coronavirus disease (COVID-19) technical guidance by WHO Laboratory testing for COVID-19 | 页面 4

Laboratory testing for coronavirus disease 2019 (COVID-19) in suspected human cases
Laboratories with limited experience in testing for
COVID-19 virus are encouraged to work with
laboratories with more experience with this
pathogen to have their initial test results confirmed
and to improve their own performance. Viral culture
Virus isolation is not recommended as a routine
diagnostic procedure.
For laboratories testing for COVID-19 virus in
countries where COVID-19 was not previously
circulating, WHO advises the confirmation of
testing results for: 6. Reporting of cases and test results
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Laboratories should follow national reporting
requirements. In general, all test results, positive or
negative, should be immediately reported to national
authorities. States Parties to the IHR are reminded of
their obligations to share with WHO relevant public
health information for events for which they notified
WHO, using the decision instrument in Annex 1 of
the IHR (2005) (28).
the first 5 positive specimens,
the first 10 negative specimens (collected
from patients that fit the case definition)
by referring them to one of the WHO reference
laboratories providing confirmatory testing for
COVID-19. For national COVID-19 laboratories
that require support with specimen shipment to one
of the reference laboratories for testing confirmation,
a WHO shipment fund is available. Please refer to
the WHO website for the most updated list of
reference laboratories and shipment instructions.
7. Research toward improved detection
of COVID-19 virus
Serological testing
Serological surveys can aid investigation of an
ongoing outbreak and retrospective assessment of
the attack rate or extent of an outbreak. In cases
where NAAT assays are negative and there is a
strong epidemiological link to COVID-19 infection,
paired serum samples (in the acute and convalescent
phase) could support diagnosis once validated
serology tests are available. Serum samples can be
stored for these purposes.
Cross reactivity to other coronaviruses can be
challenging (24) but commercial and non-
commercial serological tests are currently under
development. Some studies with COVID-19
serological data on clinical samples have been
published (25,26).
Many aspects of the virus and disease are still not
understood. A better understanding will be needed
to provide improved guidance. For example:
Viral dynamics: optimal timing and type of clinical
material to sample for molecular testing
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Viral sequencing
In addition to providing confirmation of the
presence of the virus, regular sequencing of a
percentage of specimens from clinical cases can be
useful to monitor for viral genome mutations that
might affect the performance of medical
countermeasures, including diagnostic tests. Virus
whole genome sequencing can also inform
molecular epidemiology studies. Many public-
access databases for deposition of genetic sequence
data are available, including GISAID, which is
intended to protect the rights of the submitting party
(27).
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Dynamic of immunological response
Disease severity in various populations, e.g.
by age.
The
relationship
between
viral
concentration and disease severity
The duration of shedding, and relation to
clinical picture (e.g. clinical recovery
occurs with viral clearing, or shedding
persists despite clinical improvement)
Development and validation of useful
serological assays
Comparative studies of available molecular
and serological assays
Optimal percentage of positive cases that
requires sequencing to monitor mutations
that might affect the performance of
molecular tests.
WHO encourages the sharing of data to better
understand and thus manage the COVID-19
outbreak, and to develop countermeasures.
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