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Course: Clinical Analysis
Lecturer: Dr. Weam Saad
Lecture
:
Clinical laboratory specimens
Clinical laboratory specimens
Before receiving any sample we must be sure of the followings:
1. The patient did the right during giving sample (like giving urine
sample during midstream).
2. The sample is labeled with name, date and test and well sealed or
closed in appropriate containers to avoid samples contamination
especially those for culturing.
3. The time for operating tests is important because some samples will
be useless when stored for long time like swabs for culturing.
4. The environmental conditions of storage for samples are important to
notice.
5. The quantity of specimen if it is enough to do the ordered test, e.g.
blood for serological tests.
Specimens Types:
Any clinical laboratory expects the following specimens:
1. Urine sample.
Can be used for general urine examination GUE, urine culture and
antibiotic sensivity tests or for sugar test.
2. Blood sample.
Can be classified for to types:
A. Whole blood:
When the blood was collected in tubes with anticoagulant e.g.
EDTA and Heparin, the blood will not be clotted whole blood is
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usually used for total W.B.C count, complete blood film or differential
W.B. Count, ESR (erythrocytes sedimentation rate), the work with
whole blood need for gentle because R.B.C.s are able to be broken
easily and cause hemolysis then sample will be useless.
Sometimes whole blood collected in special containers with
EDTA and iodide will be used for decontaminate containers surface.
This sample will be used for blood culturing in bacteremia cases e.g.
Brucellosis
.
B. Serum:
When the blood is collected in ordinary tubes without anticoagulant,
then blood will be clotted, serum (yellow liquid) will be separated by
centrifugation and moved to other clean tube, serum is the most
common sample used in clinical laboratories tests, it can be used for
wide broad of tests e.g. Serum Sugar (fasting or random), Creatinine,
Rose Bengal, widal, and others.
3. Stool sample (feces):
The most common test ordered for feces samples is General Stool
Examination (GSE), mainly for diarrhea and dysentery cases,
sometimes physician needs stool culture for antibiotic sensitivity test,
in addition, some specialized clinical laboratories generate parasite
detection tests using feces samples for detecting parasitic stages like
ova, trophozoite, cyst.
4. Cerebrospinal fluid
(CSF):
Using of this sample is limited with some laboratories and used for
CSF film or culture and these tests are ordered in some cancer cases,
encephalitis and meningitis.
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5. Seminal fluid:
This specimen used for seminal fluid test
(SFT), usually during
male infertility cases for counting number and detecting viability,
activity and abnormal forms, also other items involved in this test, and
rarely need culturing .
6. Organs and tissue for histopathology:
These samples are limited with special laboratories and ordered for
the diagnosis and identification of cancer and malignant tumors and
usually performed by specialized physician with histopathology.
7. Swabs:
A wooden cotton stick satirized or a disposable one with special
container. These swabs are usually used for culture and antibiotic
sensitivity test to determine the most effective antibiotic for treatment.
Abscess and exudates from infected area like tonsils, middle ear,
wounds, nose, etc. The most important part during taking swab samples
is to serialize the skin or neighboring area (if possible) before take the
swab to avoid contamination with normal flora or other organisms like
fungi.
8.
Sputum
:
This sample usually used for culturing and antibiotic sensitivity test
during pneumonia and other respiratory tract infections
(RTI). This
sample can be used for smear preparation also.
9. Skin scales:
These samples can be taken by infected skin
scratch and usually
used for slides preparations using special stains for fungi and molds
detection. Sometimes they are used for culturing in special media for
further diagnosis.