Student: TENG CASSANDREA
Topic: Histology/ LMQA
On my first day of work I was posted to the histology laboratory where they dealt with tissue processing. The scope of the laboratory’s work consisted of:
Receiving of specimens
Tissue processing by tissue processor
Embedding
Paraffin sectioning
Frozen sectioning
Staining by autostainer or manual special staining
Cover slipping and labeling
Immunohistochemistry
Some of the procedures that I observed were:
Receiving specimens
Check the information on the requisition form against labels on the specimen bags and bottles to check if they match (reduces error).
Requisition forms come in pairs; yellow and white forms.
Yellow forms are kept in case of error (easy traceability).
When no errors detected, the forms are signed by the lab tech that received the samples(acountability).
Specimens kept in order in rack and request information are manually entered into database (LIS).
Paraffin sectioning
For good sections, must operate microtome at constant rate.
Must not section to fast as tissue may become damaged or even ‘disappear’ (too much tissue is cut off).
Freezing the block will enable thinner sections.
Levels of sectioning (1, 2, 3) reflects the depth of sectioning; the deeper the tissue is cut, the higher the level.
Working out bubbles and folds in section is done in a 45 degrees Celsius water bath.
After fishing for the sections, the slides with sections are placed into an 85 degrees Celsius oven for 15 minutes to enhance tissue adherence to slide.
Hard tissues like fibroid and bone tissues are softened first by softlen or de-cal solution.
Water bath cannot be too hot as tissues may ‘disperse’.
Request for full face (FF)à tissue is initially not fully exposed when sectioned hence a request for the ‘fuller’ view of tissue.
Sometimes ribbons have holes during sectioning. This is due to poor processing; wax did not penetrate through the tissue.
Frozen sectioning
o Rapid diagnosis of tumors and carcinomas using the cryocut.
o For patients still on operation table (OT).
o Uses rapid H&E method as report has to be submitted in 20 minutes.
o Uses the O.C.T compound; O.C.T. compound is an embedding medium for frozen tissues to ensure Optimum Cutting Temperature.
o Sometimes surface is not leveled so cryomold is used.
Embedding
o Use different size of molds depending on size of tissue
o During embedding, tissue must be orientated in such a way that gives FF; the inner and outer layer must also be seen (e.g. ovarian cyst)
o Once wax is added to mold and tissue is embedded, leave in ice; this aids in easy removal of block from mold.
o Colored paper is embedded at the back of the block (traceability of medical technologist (MT) that did embedding)
When embedding, tissues are pressed down to ensure that tissue is leveled. this ensures that not only one part of the tissue is exposed first when sectioning.
o Scanty tissues like endothelial tissues are placed in gel and between sponges or filter bag to ensure that tissues are not lost during processing.
o Sponges are not used for big tissue as it covers the cassette holes making it difficult for the wax to penetrate the tissues(poor embedding).
Lab automation (LMQA)
Some equipment in the laboratory are:
Autostainer
Autocoverslipper
Bondmax ( immunohistochemistry)
Shendon Celsior (tissue processor)
These equipments help increase the laboratory’s productivity rate which in turn increases efficiency of laboratory.
Some practices that I observed (LMQA/QC):
Counter-checking of label on slides with printed labels and paraffin block(check morphology on slides and in block to match)
After staining, counter-check slides with a control to see if its up to standard.
Control run in autostainer before patient sample to check if H&E is of quality.
Staining manual consist of policies and procedures (policy number ,revision date, effective date, approved by, applies to)
Daily updating of QC checklist (waterbath, oven, autostainer, tissue processor, etc)
Lab safety aspect
The hospital that I’m posted to is well equipped with safety gears and has many safety measures installed in case of an emergency. Some examples are:
Safety blankets
Eye wash and shower stations
Separate chemical stores
Fire trigger points
Emergency exits
Radiation safety (isotopes;lazers)
Bio-safety (infectious material;BSC)
Electrical safety
PPE (googles,chemical-resistant gloves, masks, lab coats, chemical boots)
Laboratory safety training (training checklist; lab safety talks and videos)
So this was what i did in my first week...oh and i watched an autopsy also... damn bloody..!! lol... anyways i'll keep you guys updated... cheers..!
