Coronavirus disease (COVID-19) technical guidance by WHO Investigation protocol for COVID-19 | Page 10

3
Laboratory evaluations
Laboratory and biosafety guidance for COVID-19 can be found on the WHO website.
Serologic assays specific to COVID-19 are currently under development / in the process of
evaluation. The protocols or SOPs will be published on the WHO website once they become
available. Cross reactivity to other coronaviruses may be an issue and should be considered in the
interpretation of data. Multiple assays may be required to confirm a seropositive for COVID-19 virus.
Laboratory procedures involving sample manipulation must be carried out in a biosafety cabinet
(BSC).
3.1
Serological testing
Serum samples should be screened for the presence of COVID-19 virus specific antibodies using
serological testing. Tests for both IgM and IgG should be carried out using an enzyme linked
immunosorbent assay (ELISA) or immunofluorescence. If a sample is positive for either IgM or IgG a
plaque reduction neutralization test (PRNT) should be done.
ELISA testing should be carried out in a facility with at least biosafety level 2 (BSL-2) capacity.
3.2
Confirmation of the presence of neutralizing antibodies
A PRNT can be carried out on samples that were positive for COVID-19 specific IgM or IgG
antibodies to confirm the presence of neutralizing antibodies.
PRNT should be carried out in a facility with at least BSL-3 capacity.
3.3
Sample storage
In the case that serum samples cannot be processed immediately, they should be stored at -80°C. It
is recommended to aliquot samples prior to freezing, to minimize freeze thaw cycles.
COMMENT: These recommendations are subject to changes as new, reliable serological assays
become available.
COMMENT: If serological testing is not available in the country in which serum samples are
collected, they may be stored or shipped to an international reference laboratory. WHO is able to
facilitate communication with international referral laboratories in order for samples to be shipped
for further testing.
10