CLINICAL LAB SCIENEC

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ESSENTIALS OF CLINICAL LABORATORY SCIENCE
In the Lab
HDL Calculation (Manual Method)
HDL (mg/dL) =
Abs of unknown (Au) × 50 (concentration of the
standard) (mg/dL)
Abs of standard (As)
Critical Reminder
The cholesterol procedure, unlike the
previous examples, uses a kinetic
reaction to measure the change in
absorbance as a substrate, a product on
which an enzyme works specifi cally
(Figure 14-3). This test requires a factor
determined from a number of assay
conditions on which the reaction is
dependent. The previous chemistry
procedures were based on an end-point
reaction, where a color is produced that
correlates in intensity with the
concentration of the component being
measured. Most product inserts found
in the test kits will provide all of the
information needed to understand and
perform the procedure. Most automated
chemistry analyzers use these kinetic
methods, which measure the change
rather than an end-point. This gives a
more accurate and rapid analysis than
that of the end-point reactions, which
must sit for a period of time for the
color to develop.
12. Discard all supplies used for the procedure in the appropriate containers. A
disinfectant should be used to clean the work surfaces and equipment should
be cleaned and restored to its former position. Gloves should be
discarded appropriately and the hands washed thoroughly in accordance
with established policies.
Quality Control
Two levels of control material with known cholesterol levels determined
by this procedure should be analyzed each day of testing in a
medical laboratory.
Linearity
When performed as directed, the method is linear from 0 to 200 mg/dL.
Reporting of Results
Report your findings from the Total Cholesterol and High-Density
Lipoprotein (HDL) procedure in the form supplied by your instructor.
Results of total cholesterol and HDL are reported in milligrams per
deciliter (mg/dL).
MANUAL CHEMISTRY PROCEDURE #4
AST/GOT (Manual) Chemistry Procedure
Principles
This test is for the quantitative determination of serum aspartate aminotransferase
(AST), needed in the diagnosis and treatment of certain
types of liver and heart disease. Organ cells deteriorate under certain
conditions (e.g., infection, diminished blood flow). The death of these
cells releases enzymes that are richer in some organs than others.
The physician can rule out certain ailments or suspect others based
on this test. Usually, a battery of enzymes tests are run and the results
compared for significance.
A working reagent is prepared by reconstituting a substrate upon which the enzyme
AST will react. The working reagent is prepared by pouring the contents of a small
AST additive (substrate) bottle into a larger AST reagent (coenzyme) bottle. Replace
the cap and mix well by gentle inversion (do not shake vigorously). For ease in transferring
the working reagent, some kits provide a flip-top cap to replace the screw cap.
The absorbance of freshly prepared working reagent should be at least 1.200 when
measured at 340 nm in a spectrophotometer with a 1-cm light path. The reagent
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