[Histonet] Formalin fixation for COVID-19 positive tissues .....

[E. Wayne Johnson]

Where aldehydes are used for disinfection we consider 30 minutes contact time
for difficult viruses like African Swine Fever (ASF) virus to be adequate.  Coronaviruses
like PEDv TGE IBV and the SARS virus are much easier to inactivate than ASF virus.
I'd consider the SARS virus to be similar to Infectious Bronchitis Virus which is systemic
and affects a wide variety of tissues.

Inactivating a virus in a chunk of tissue is more challenging than disinfection of contaminated
fomites but I see no reason to think that routine fixation times would not completely inactivate
the SARS coronavirus.  The concentrations of aldehyde for fixation are at least 10 times higher
than the highest concentrations used when aldehydes are employed for disinfection.

I'd be more concerned about the container than the contents.

For necropsy samples from your human specimens there is not generally any rush to get the results
so the CDC's C.Y.A. time doesn't cause trouble but waiting 72 hours for a surgical path result
would seem to be just wasting time.

E. Wayne Johnson DVM
Enable AgTech
Beijing


Tony Henwood (SCHN) via Histonet wrote:
> Hi Richard,
>
> It will depend on the size of the tissue and the source.
> Lung tissue is the major concern. Other tissues not affected as much (based on the burgeoning literature on Covid-19).
> Routine fixation time are applicable, remembering that the alcohols and heated wax will also inactivate the virus (triple whammy).
> I suppose that I better add a reference:
>
> https://www.tandfonline.com/doi/full/10.1080/01478885.2020.1734718
>
>
> -----Original Message-----
> From: Cartun, Richard via Histonet [mailto:histonet at lists.utsouthwestern.edu]
> Sent: Tuesday, 21 April 2020 6:51 AM
> To: histonet at lists.utsouthwestern.edu
> Subject: [Histonet] Formalin fixation for COVID-19 positive tissues .....
>
> How long are you fixing surgical tissue specimens from COVID-19 positive patient's before tissue processing?  I know that the CDC is recommending "72" hours for autopsy tissues, but, to me, that seems excessive for surgical pathology specimens.  Any information that you can share on this subject would be appreciated.  Thank you and stay safe.
>
> Richard
>
> Richard W. Cartun, MS, PhD
> Director, Histology & The Martin M. Berman, MD Immunopathology/Morphologic Proteomics Laboratory Director, Biospecimen Collection Programs Assistant Director, Anatomic Pathology Hartford Hospital
> 80 Seymour Street
> Hartford, CT  06102
> (860) 972-1596 (Office)
> (860) 545-2204 (Fax)
> Richard.cartun at hhchealth.org<mailto:Richard.cartun at hhchealth.org>
>
>
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