CLINICAL LAB SCIENEC

234
ESSENTIALS OF CLINICAL LABORATORY SCIENCE
Critical Reminder
Key Elements of an Effective
Quality Assurance Program
• Vision and goals of the organization,
often incorporated
institution-wide
• Competence of laboratory personnel
through initial qualifications,
continuing education, and training
as jobs change
• Proper equipment for the work
being performed
• Fiscally sound policies for
purchasing equipment and
maintenance of supply inventory
to control excessive costs
• Process control using statistics
and engineering discipline for
controlling the output of a specific
process, e.g., medical laboratory
reports
• Accurate and adequate recordkeeping
in a safe manner
and for the amount of time
prescribed
• Safety and security of stored
documents such as medical
reports and medical records
• Incident report filing and
follow-up, sometimes called
occurrence management
• Continuous assessment of processes
by an internal policing
system to detect failures
• Process improvement—systems
should be improving and actions
taken to make improvements by
learning from mistakes
• Patient questionnaires on discharge
or shortly thereafter to indicate dissatisfaction
or praise for individuals
or the institution
of light transmitted through the sample and reagent combination
following a reaction between the two. In this method, the resulting
reaction produces a characteristic color, which differs by the specific
test type being performed. Some enzymatic reactions are used in the
end-point methods, but most enzymatic reactions are measured as
a rate reaction at a wavelength not visible to the naked eye (ultraviolet
range). This reaction is measured in the same way as the endpoint
methods except that the reaction is ongoing while the sample is
being read, giving a rate change for a given amount of time, while the
end-point reaction is allowed to complete the reaction, usually 5 to
10 minutes.
Reading of QC samples uses the spectrophotometer in chemistry
and in some other areas of the laboratory as well. Maintenance and care
of the spectrophotometer are necessary on a routine basis to maintain
good QC. Deteriorating and dirty spectrophotometers will adversely
affect QC results, leading to the conclusion that the QC sample itself is
inaccurate through contamination or faulty reconstitution. When light
of an appropriate wavelength strikes a cuvet that contains a colored
sample, some of the light is absorbed by the solution; the rest is transmitted
through the sample to the detector. The proportion of light that
reaches the detector is known as percent transmittance (%T) and is
represented by the following equation:
Intensity of light transmitted through sample/
Intensity of light striking sample × 100 = % T (transmittance)
The general rule in regard to Beer’s law is that as the concentration
of colored solution in a cuvet is increased, the %T is decreased.
Control samples may contain both end-point reactions and kinetic
rate reactions. Other methodologies, such as those using ion-selective
electrodes, are not discussed here.
QC Terminology
QC programs are an integral and vital component of quality assurance
programs and are required as a condition of both accreditation
and licensure for the medical laboratory. A number of terms have
evolved relative to QC programs over the years and it is necessary
to understand the meaning and the intent of the functions that these
terms denote (Table 10-1).
The following is a list of three of the most common charts used in a
QC program. Any or all of these may be used in the laboratory.
• Levey-Jennings charts show daily values in a graph form. The mean
will be shown across the middle of the chart. Both negative and
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