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1. Discuss the classification criteria for evaluating histological artefacts?
Ans:
Classification criteria should include artefacts that are generated prior to being received in the laboratory :
- Pre- analytical :-
a) Tissue dehydration prior to fixation issues
b) Mechanical trauma or damage to the tissue due to surgical procedures which directly affects the tissue. These would include
c) Crushing/ pinching effects of the tissue from the forceps used to remove the tissue sample from the patient.
d) Leaching of autolytic lysozymes from ruptured cells resulting in localised tissue damage
e) Fragmentation of the tissue
f) Haemorrhagic changes as a result of rupturing blood vessels.
Other artefacts are generated once they are being processed through the laboratory and these are called
- Post analytical:
a) Fixation artefacts
b) The specimen dissection artefacts
c) Tissue processing artefacts
d) Embedding artefacts
e) Microtomy artefacts
f) Staining both tinctorially and immunocytochemically based artefacts
g) Coverslipping and mounting of tissue sections artefacts
h) Automated machine failures resulting in artefacts in dehydration (processing machines), embedding (tissue embedding machines), Staining (automated stainers) and coverslipping (automated coverslippers).
i) Molecular contamination artefacts
j) Miscellaneous caused artefacts.
There are many more unusual artefacts that can be generated, many of these are more unusual and rare but can occur. The well trained laboratory workforce will understand where and how these artefacts arise and will take preventative actions to minimise their impact. Needless to say a clean and well managed laboratory will reduce the incidents of artefacts in the working environment.
2. Discuss the impact of automation on the range and scope of artefacts in the modern histopathology laboratory?
Ans:
This is an interesting question in the sense we can assume that increased automation within the modern histopathology laboratory will reduce the predominantly man made artefacts that we can commonly see in those laboratories that do not use widespread automation. The reality is somewhat different in the sense that with automation we often introduce a range of different artefacts that arise due to the automated process and can look sometimes quite different.
These will include the following:-
a) Over heating of tissue specimens producing drying and shrinking artefacts
b) Breaking and fracturing of slides during staining on automated platforms.
c) Uneven staining due to failure to cover entire tissue sections with staining or antibody solutions
d) Uneven or inappropriate automated coverslipping producing excessive bubble formation under the coverslip.
e) Staining precipitation artefacts
f) False positive and false negative staining patterns due to failure to apply specific reagents within a complex sequence of staining procedures. For example in automated immunocytochemistry or in-situ hybridisation staining techniques.
g) Contaminated or failed quality assured automated reagents. This can produce a significant increase of a specific artefact affecting a wide volume of test slides in a similar fashion.
Guy Orchard