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Methodology Guidelines
counting of cells in a haemocytometer. This is a device that
defines a precise volume between a special glass slide and a
coverslip. By counting the total number of cells within this
volume, the cell concentration within the specimen can be
accurately determined. While more accurate than simply
using a coverslip on a standard slide, the extra precision of
this method is not usually required for successful Cytospin
preparations.
A third method for determination of cell number is by
use of a cell counter of the electronic volume sensing type
(Coulter counter). This instrument can provide a precise
evaluation of a cell sample. It does require sufficient amount
of sample however, which may not always be available. It is
common to determine the cell number of specimens using
this instrumentation in the haematology laboratory. Any
specimen obtained from the haematology laboratory may
include cell number (or concentration) information.
It is important to recognise that samples that are quite
concentrated should be handled carefully. For example, if
the specimen is so concentrated that only a single drop may
be required, the addition of a second drop will double the
cell concentration. It is preferable to work with specimens
that are dilute enough that five or six drops are required for
the preparation. With such a specimen, the addition of one
more drop will not be as likely to result in overlapping cells
in the final Cytospin preparation.
While it is common to discuss sample sizes in terms of
'drops', it is important to realise that drop size will be
dependent on the type of pipette used to transfer the
specimen. As an example, a Falcon 3 ml transfer pipette
will dispense approximately 0.5 ml in 15 drops. A six inch
glass Pasteur pipette will dispense 0.5 ml in 20 drops.
It is advisable to standardise on a single pipette type for
all cytological preparations, otherwise 'drops' will be a
meaningless measurement.
Specimen
Many cytological specimens arrive in the laboratory as
Enrichment
A78310250ES 5.1ª Edición
Manual de operaciones de la Cytospin 4
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