HOSPITAL LABORATORY TESTS
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Report
delivered to
doctor
Initial
examination
of patient by
doctor
Action
Initiates
request
Sample(s)
from patient
Transport
Laboratory
reception
Specimen
identification
Laboratory
worklist
Specimen
preparation
Specimen
aliquots
Result(s)
Calculation(s)
Analysis(es)
Quality
control
Report
Report
evaluation
Reexamination of
patient &
interpretation of
report by doctor
Figure 1.18 Sequence of events involved in
obtaining a clinical test result.
For some analytes, the blood must be collected into a tube containing an
anticoagulant or preservative. Specimens of blood for glucose determination
must be collected into a tube containing fluoride ions (Fâ) since this inhibits
glycolysis and prevents the utilization of serum glucose by blood cells.
Occasionally blood is collected into the wrong tube and then decanted into
the correct tube. This can cause a number of problems. For example, blood
collected into a tube containing ethylene diamine tetraacetate (EDTA) will be
unsuitable for the determination of serum Ca2+, since EDTA is an anticoagulant,
works by chelating and removing available Ca2+.
The transport of specimens and their storage must be considered carefully
since an inappropriate environment can influence the values of clinical test
results. Swabs, for example, obtained during a microbiological investigation
of an affected site, contain only a small volume of specimen and dry easily.
They therefore need to be transported to the laboratory as quickly as possible
Figure 1.19 Photograph of some tubes used in
the collection of clinical specimens. Courtesy of
BUPA Hospital, Manchester, UK.