On Wed, 15 Dec 1999 20:21:08 -0800,
Russell Farris <tryggvi at email.msn.com> wrote:
> When you doctor gets a white blood cell (WBC) count, are the kinds
> of WBCs usually broken out?
CBC analysis is most commonly done by automated cell counting
instruments these days. The counters generally use a method
in which the cells flow (approximately single file) through a
narrow gap. A change in electrical impedance across this gap
marks the passing of each cell. Events are accumulated and
used with the known flow rate to calculate cell counts.
The total WBC is subdivided into monocytes (called macrophages
when in tissue), lymphocytes, and granulocytes. The grans may
be further subdivided into eosinophils, neutrophils, and basophils.
A WBC with differential includes reporting of some (or all) of
these subsets, and is a standard capability of modern hematology
analyzers.
Subset counts are often based on the size of the cell. The
size of the cell is estimated from the magnitude of the impedance
change, although optical methods (scatter of laser light) are
becoming more common.
Another means of differentiating leukocyte subsets is based on
their uptake of various dyes. The traditional manual counts rely
on these techniques. Newer approaches such as flow cytometry
use the binding of monoclonal anitbodies to distinguish between
even smaller subsets of white cells, particularly lymphocytes.
Ted
--
Theodore Heise <theise at netins.net> West Lafayette, IN, USA
