CLINICAL LAB SCIENEC

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ESSENTIALS OF CLINICAL LABORATORY SCIENCE
Timely collection and proper transport are extremely important if accurate
results are to be produced. When analyzing specimens, results must be precise,
sensitive, accurate, and specific. Ingestion of certain foods and certain medications
may alter dramatically the values obtained from blood testing. A number
of laboratory determinations require an overnight fast, and those who are being
tested after a fast must be informed of the possible effect of eating or of chewing
gum or tobacco. Certain values are higher at certain times of the day or night,
and it is vitally important to collect the specimens at the proper time or the
results will be useless for determining if abnormalities are present. Specific and
consistent levels must be maintained for certain medications as the therapeutic
range is very narrow for some types of drugs. Some medicines are also toxic at
certain levels and may cause permanent damage or even death if the values rise
above those levels. Therefore, timed specimens are drawn for a number of medications.
An example is a group of drugs called generally “hospital antibiotics”
because they are only administered to an inpatient, normally by IV injection.
For many of these, peaks and troughs are established where the concentration is
within a therapeutic range but is not allowed to rise to a toxic level.
Categories of Errors
Errors fall into three categories and they may affect patient care if they result
in the reporting of erroneous results. Errors may occur before testing begins
(preanalytical), during the test procedure (analytical), and following completion
of the test (postanalytical) with handling of the data. Remember that analytical
errors may occur during performance of the tests, and in an autoanalyzer, a
hundred samples may be relatively accurate, and one sample may be extremely
abnormal, and often the cause is never determined.
Preanalytical
Errors caused by the failure to adhere to all of the procedures required to ensure
that the sample was adequate and was properly identified fall into this category.
Preanalytical errors occur outside the laboratory during the collection of specimens,
such as mislabeling the tubes, using the wrong preservative required for a
particular procedure, collecting blood in the wrong tube(s), having inadequate
volume of a specimen, or collecting a specimen from the wrong patient. Other
preanalytical errors include mistakes by the physician by requesting the procedure
on the wrong patient or hospital medical personnel failing to submit a
timely request to the laboratory. Another common error in this category is that
of the patient who should be fasting but eats a meal or is given a meal by the hospital
personnel or a visitor. Errors of this nature are among the most difficult to
determine and to remedy. The delay in obtaining meaningful results often results
in an increased hospital stay or failure to initiate needed treatment and may even
cause permanent damage to the patient.
Analytical
These errors occur inside the laboratory after the specimen is collected and properly
transported to the laboratory and even to the correct department. These
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