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Cellular Pathology: Factors that affect performance and interpretation


Histology

Ensure all samples are placed immediately into 10% Neutral Buffered Formalin (NBF). A delay may lead to a loss of morphology through autolysis and putrefaction, affecting the interpretation.

All samples must be placed in containers that have at least 10 times the volume of 10% NBF, when compared with the size of tissue. Placing tissue into a container that is not large enough will lead to the tissue being distorted and poor fixation.

Please note, all histology tests have been verified using 10% NBF. Due to the nature of histological samples (most samples cannot be repeated) the department will not currently reject samples received in 10% formal saline. These samples will be transferred to 10% NBF at the earliest opportunity.

 

Diagnostic Cytology

Cytology samples not being delivered and received by the lab ASAP

  • These specimens (unless they have been placed in cytospin collection fluid) do not contain any preservatives/fixatives that prevent the cells from deteriorating or prevents microbes from growing. The longer a specimen takes to reach the lab there is an increased chance that the cells will deteriorate and that the sample may become unsuitable for diagnosis.
  • CSF cells deteriorate rapidly, so a delay may mean that a diagnosis may not be possible.

Delayed samples not being refrigerated (4°C)

  • These specimens (unless they have been placed in cytospin collection fluid) do not contain any preservatives/fixatives that prevent the cells from deteriorating or prevents microbes from growing. Placing them in a fridge will help to slow down cell deterioration and microbial growth, especially important with urine samples.

Patient not being prepared properly and therefore not obtaining the best sample possible

  • If serous fluid is being sampled and the patient has been supine for a long time it is important to get them to sit up and move a little to re-suspend the cells that have settled.
  • Sputum samples should be taken first thing in the morning before patient has eaten or brushed their teeth.
  • Sputum samples need a very deep cough and it is recommended that this is obtained by a physiotherapist. If this is not done the sample may just be saliva.
  • Early morning urine should be avoided because the cells will appear degenerate and interpretation will be difficult.

FNA technique inadequate

  • Sample does not contain the cells needed to make a diagnosis and may be heavily blood stained.

FNA smears inadequate

  • If sample is too thick the viewing of cells down the microscope is difficult, only a small drop of sample needed.
  • If sample is all over the slide, cells at the sides of the slide may be lost or uninterpretable.
  • Cells squashed/smashed when slide pressure applied was too great.

FNA smear incorrectly fixed

  • Slow drying causes air drying artefact where the cells appear bigger and lack definition.
  • If the slide is incorrectly labelled wet or dry, the wrong stain may be applied in the lab making interpretation difficult.

FNA smear on back of slide

  • If the smear is placed on the back of the slide and not the front, cells or even the whole sample might be removed when being handled by lab staff.