Fixation on Histology

Prior to my retirement, I worked for about 25 years in pharmaceutical laboratories, which handled various animal specimens. Being a pharmaceutical lab, we had specific protocol we followed for each study type received, and for the most part these procedures served us well, however like with any complex system, we soon found that the smallest change could make the biggest difference.

For example, one day, one of our pathologists noticed an issue with rodent liver fixation.  I reviewed the liver sections with him microscopically and saw cracking throughout most all liver sections on his study.  I started investigating what could have happened.  I looked up the study in our processing logs and the study was processed on the appropriate program.  I checked reagent change logs and the processor had run another study the day before.  I checked that study for liver issues and there were none.  I checked with the necropsy lead tech for the problem study and there wasn’t anything unusual that occurred while the necropsy was performed.  We reviewed the formalin log for lot number, then checked the lot number.  It had been used on several studies with no issue.  I spoke with several of the necropsy techs to find out if there were any deviations to procedure during this necropsy, and none were recorded or remembered.  Each rodent necropsy after the problem study resulted in the same issue but became worse and spread to other tissues.  We were looking into anything that we could think of that had changed because we couldn’t find any processes in our lab that were different or reagents that were out of order or incorrect.  We changed the formalin on the processor every run to ensure fresh formalin was being used to enable the best fixation possible and we still had cracked tissues.  Sometimes we had improvements and other times worse.  Only after speaking with our QA (quality assurance) department about another study question did I find out that the necropsy team had discontinued using an agitation table that the tissue containers were placed onto after each animal tissues were in fixative.  I revisited the necropsy supervisor and discovered that the team had discontinued using the agitation table because the QA reviewer during the original “problem study’ had questioned how long each animal was under agitation.  Since it wasn’t timed, the QA reviewer suggested they discontinue use as the FDA might have issue with this practice.  I requested the agitation tables be placed into the Histology Laboratory and we instituted the ‘shaking’ in our lab upon receipt of the study.  We amended our SOP to include agitating tissues overnight upon receipt and our issue was solved.  Sometimes changes in another area’s processes can change our results so when you are trying to resolve an issue look to any area that handles your samples.  Sometimes it’s outside of our hands when problems occur.