Clinical Chemistry
Clinical chemistry (also
known as chemical pathology, clinical biochemistry or medical
biochemistry) is the area of chemistry that
is generally concerned with the analysis of bodily fluids for diagnostic and therapeutic purposes.
It is an applied form of biochemistry (not
to be confused with medicinal chemistry, which involves basic
research for drug
development).
The discipline originated in
the late 19th century with the use of simple chemical
reaction tests for various components of blood and urine. In the many decades
since other techniques have been applied as science and technology have
advanced, including the use and measurement of enzyme activities, spectrophotometry, electrophoresis,
and immunoassay.
There are now many blood tests and clinical urine tests with extensive
diagnostic capabilities.
Most current laboratories are
now highly automated to accommodate the high workload typical of a hospital
laboratory. Tests performed are closely monitored and quality controlled.
All biochemical tests come
under chemical pathology. These are performed on any kind of body fluid,
but mostly on serum or plasma. Serum is the yellow watery
part of blood that is left after blood has been allowed to clot and all blood
cells have been removed. This is most easily done by centrifugation, which
packs the denser blood cells and platelets to the bottom of the centrifuge
tube, leaving the liquid serum fraction resting above the packed cells. This
initial step before analysis has recently been included in instruments that
operate on the "integrated system" principle. Plasma is in
essence the same as serum, but is obtained by centrifuging the blood without clotting.
Plasma is obtained by centrifugation before clotting occurs. The type
of test required dictates what type of sample is used.
A large medical laboratory will accept samples for
up to about 700 different kinds of tests. Even the largest of laboratories
rarely do all these tests themselves, and some must be referred to other labs.
This large array of tests can
be categorized into sub-specialties of:
· General or routine chemistry – commonly ordered
blood chemistries (e.g., liver and kidney function tests).
· Urinalysis –
chemical analysis of urine for a wide array of diseases, along with other
fluids such as CSF and effusions
· Fecal analysis – mostly for detection of
gastrointestinal disorders.