Due to the advent of Covid-19 and the demand for histology services on Covid-19 positive samples we have a few important notes for our customers.
-we CANNOT section or handle unfixed Covid-positive samples at this time.
-All human samples must be fixed for 72-hours at room temperature and will be assumed Covid-positive unless documentation is provided proving a negative Covid test at the time of sample collection.
-All animal Covid-19 models must be fixed for 72-hours at room temperature
-All cell or organoid Covid-19 models must be fixed as below.
Please refer to the following for specific guidelines:
Chemical fixation of cells or tissues: Most of the studies on chemical fixation used a coronavirus infected monolayer of cells in tissue culture as the samples. They tested three commonly used fixatives for histology or microscopy: 10% neutral buffered formalin, 4% paraformaldehyde, and 1:1 methanol/acetone9. A 30-minute incubation in formalin or paraformaldehyde at room temperature was sufficient to inactivate MERS-CoV; a 60-minute incubation was required for methanol/acetone. Unfortunately, there is a lack of literature regarding inactivation of coronavirus in tissue samples. The previously mentioned fixatives should inactivate coronavirus in tissue samples but there are no published details on the time needed to fully perfuse the whole of the tissue sample. The CDC Interim Guidance on Collection and Submission of Postmortem Specimens from Deceased Persons with Known or Suspected COVID-19 instructs that a tissue sample of 4-5 mm in thickness should be placed in at least 10 times the volume of the sample of 10% formalin and incubated for 72 hours for optimal fixation. Note: Paraffin embedded samples will be fully heat-inactivated because the paraffin infiltration step places the sample at a temperature of 60-65°C for around 2 hours.