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At TVCS meeting
10th November 2001 at Watford general Hospital, Veda Misir (BMS2
at the Royal Glamorgan Hospital, Wales) gave a clear and concise
talk about the Fine Needle Aspiration (FNA) procedure and a simple
FNA collection fluid that is compatible with Liquid Based Cytology
(LBC) technology.
The technical
goal of the FNA procedure is to ensure that every diagnostic cell
aspirated reaches the pathologist in optimal condition for microscopic
examination. Smear quality, together with obtaining a representative
sample and the experience of the pathologist plays a critical role
in this procedure. Technical problems that can effect smear quality
are that diagnostic cells may be trapped in needle clots, unrepresentative
material can lead to inaccuracy and in smear preparation there may
be crush artefact, inadequate fixation of "wet" smears
or diagnostic cells obscured by blood or exudate.
Attempts
to address smear quality include
- improved
training of clinicians in smear preparation,
- attendance
at FNA by technical staff and
- use of collection
fluids.
The advantages
of using a collecting fluid
- each slide
is representative of the aspirate so accurate rapid evaluation
is possible,
- delayed optimal
processing in lab is facilitated,
- cell retrieval
is maximised through needle rinse,
- there is
no need for technical staff attendance,
- there is
no need for clinical skill in smear preparation
- health and
safety issues are addressed.
The qualities of an ideal collecting fluid
- cellular
integrity and morphology must be preserved,
- routine stains
facilitated,
- any smear
processing system facilitated (direct smear, cytospin, TLC),
- allows at
least 60 hours storage,
- facilitate
ancillary techniques (eg Immunocytochemistry)
- must be cheap,
easily stored and disposed of.
Existing
fluids include alcoholic fluids that are excellent for Pap but not
for Giemsa, and non-alcoholic ones that make Pap and Giemsa stains
possible.
These latter include normal saline, RMPI culture medium(not
compatible with Thin Prep processor), and balanced electrolyte
solutions (BES).
The BES are
saline base eg Normosol or Plasmalyte and are cheap, easily available
commercially, are used intravenously so kind to cells and the aspirate
in BES is similar to native material so can be treated like a fluid
such as CSF.
ThinPrep (TP)
was introduced, at the Royal Gwent Hospital (RGH), for non-gynae
work and although the TP Paps were good there was disappointment
at the lack of TP/Giemsa facility. With the added problem that no
technical staff were available to attend FNAs, a pilot study was
set up using transport solutions compatible with conventional staining
and the TP processor, with the aim to provide a single fluid to
facilitate both TP Pap and conventional Giemsa and ensure rapid
evaluation on representative material.
This pilot
study used Plasmacyte (BES) in 2.0ml aliquots in universals, stored
at 4 C and carried out on serous fluid deposits and fresh, unfixed,
resected tumours.
The results
were excellent staining and preparations for TP Pap, Cytospin Giemsa/Pap,
direct Giemsa, Pap, H&E and Immunocytochemistry.
The main study
was carried out in collaboration with the Radiology Dept at RGH.
It took the form of a Split Sample Study allowing comparison of
conventional direct smears and Plasmalyte smears. The organs examined
included breast, liver, thyroid, lymph node and lung from which
there were 47 adequate samples. Features examined were nuclear/cytoplasmic
detail, architecture and background material.
For conventional
preps at least two direct smears were taken - one air dried Giemsa
and one wet fixed for Pap/rapid H&E. For Plasmacyte preps -
the remaining material, including the needle rinse was placed in
a Plasmacyte aliquot and processed to give - one Giemsa Cytospin
(low speed using Shandon Megafunnel) and one TP Pap.
The main study
results were based on adequate Plasmacyte samples. High quality
TP/Pap and Giemsa smears were produced, cells are concentrated so
easier to screen, Giemsa and TP Pap complement each other, there
is rapid evaluation of adequacy, ancillary studies are facilitated
and storage is possible up to 60 hours at 4 C.
The concusion
of this study is that Plasmalyte, an intravenous saline solution,
easily available from hospital pharmacies is an ideal collection
fluid for optimising FNA processing.
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