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Associate Professor Dr. Wannee Jiraungkoorskul
Department of Pathobiology, Faculty of Science, Mahidol University
Tel: 02-201-5563, E-mail: [email protected]
SCBM343- Specimen collection and interpretation
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What is clinical pathology?
• Clinical pathology covers a wide range of laboratory
functions and is concerned with the diagnosis, treatment,
and prevention of disease.
• Clinical pathologists are doctors with special training who
often direct all of the special divisions of the laboratory,
which may include the blood bank, clinical chemistry and
biology, toxicology, hematology, immunology and serology,
and microbiology.
http://www.hopkinsmedicine.org/healthlibrary/conditions/pathology/clinical_pathology_overview_85,P00955/
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What does a clinical pathologist do?
• A clinical pathologist looks at blood, urine, and other body
fluid specimens under a microscope, or with other diagnostic
tools, to observe levels of certain chemicals and/or other
substances in the body.
• A diagnosis or determination to conduct further study is then
made based on the test results.
http://www.hopkinsmedicine.org/healthlibrary/conditions/pathology/clinical_pathology_overview_85,P00955/
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Types of specimens used in clinical pathology
• Blood is used in many tests as a "whole," as plasma (the
fluid left when red and white blood cells are removed), or as
serum (a clear fluid that separates from blood when it clots).
http://www.medical-labs.net/wp-content/uploads/2014/04/Plasma-and-Serum-Comparision.jpg
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Types of specimens used in clinical pathology
• Venipuncture = Blood is usually
drawn with a needle from a median
cubital vein.
• Capillary puncture or Finger stick =
the tip of the finger is pricked and
then squeezed to draw blood.
http://www.anatomyatlases.org/firstaid/images/injectionB.jpg /
http://img.tfd.com/medical/Davis/Lab/A1.png
6 http://fajniemieszkam.eu/pic/75249-vacutainer-tubes-color-guide.jpg
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A "clean-catch" urine sample is performed by collecting the sample of urine in
midstream. Men should wipe clean the head of the penis. Women need to wash
the area between the lips of the vagina with soapy water and rinse well. A small
amount of urine should initially fall into the toilet bowl before it is collected (this
clears the urethra of contaminants). Then, in a clean container, catch about 5-10
ml of urine and remove the container from the urine stream. The container is then given to the health care provider.
Urine
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Sputum
• Sputum can be
coughed into a
clean container.
http://iacld.ir/en/images/stories/Sputum_Collection_Instructions.jpg/
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Stool
• Feces or stool is usually collected by the patient in a clean
cardboard or plastic container.
http://www.harrisoncountyhealth.com/poo.jpg
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A nasopharyngeal culture is a test used to identify organisms that can be in nasal secretions causing disease.
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A CSF cell count is a test to measure the number of red and white blood cells that are in CSF.
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• Lumbar puncture = A small amount of bone marrow is removed during a bone marrow aspiration. The marrow can be studied to determine the cause of anemia, the presence of leukemia or other malignancy.
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• Abdominal paracentesis = A peritoneal fluid is withdrawn with a needle from the peritoneal cavity. The peritoneal cavity is the space between the two membranes lining the abdominal cavity. The test is done to determine the cause of ascites, fluid accumulation in the peritoneal space.
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• Thoracentesis = A sample of pleural fluid is withdrawn by a needle. The test is performed when infection of the pleural space is suspected or when an abnormal collection of pleural fluid is noticed by chest X-ray.
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• Pericardiocentesis = During a pericardial fluid culture, a small needle is inserted into the chest between the ribs into the pericardium (the thin sac that surrounds the heart) and a small amount of fluid is withdrawn.
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• To obtain a synovial fluid sample, a needle is inserted into the knee between the joint space. When the needle is in place the synovial fluid is then withdrawn.
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• In amniocentesis a hollow needle is inserted into the mother's
abdomen into the uterus, and amniotic fluid is drawn for analysis.
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• A bronchoscope (a thin, flexible fiberoptic tube) is often used to obtain the lung tissue sample. Evidence of infection such as abscesses, inflammation, or abnormal secretions may be observed during the procedure.
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• A sample biopsy of esophageal tissue is obtained by placing a tube through the mouth into the esophagus where small instruments grab a portion of esophageal tissue for examination. The test is performed when infection or other diseases of the esophagus are suspected, or an ongoing infection does not respond to treatment.
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• A flexible fiberoptic tube is passed through the mouth and down the esophagus until it enters the stomach. The tube allows the health care provider to see the various parts and take a biopsy. The procedure is used to determine the cause of bleeding, and to diagnose tumors, ulcers, inflammatory disease, and structural abnormalities of the stomach.
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• A duodenal tissue biopsy is performed by inserting a special tube through the nose or mouth down into the duodenum. When the tube is in place, it suctions out some of the fluid located in the duodenum.
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• Lymph node biopsy = a needle is inserted within the lymph node and a sample of fluid is sent to the laboratory.
23 • Liver biopsy = a needle is inserted into the liver and a tissue sample
is withdrawn and sent to the laboratory for testing.
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• Renal biopsy = a small sample of kidney tissue is removed with a needle. The test is sometimes used to evaluate an unexplained decrease in kidney function, persistent blood in the urine, or protein in the urine.
25 • A bile culture test is performed to see if there is infection in the
biliary tract.
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• A vaginitis test looks for the cause of vaginal irritation and discharge, which is usually a yeast, bacterial or parasitic infection.
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• The presence of blood in semen (the fluid discharged upon
ejaculation) may be caused by inflammation, infection, obstruction
or trauma.
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Purposes of laboratory tests
1. They are used for
a. Mass screening e.g., Phenylketonuria in newborns
b. Screening asymptomatic patients e.g., Mammography
c. Screening symptomatic patients e.g., Stress
electrocardiogram in a patient with chest pain
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2. They are used to confirm a diagnosis e.g., coronary
angiogram to confirm coronary artery disease in a patient
with a positive stress electrocardiogram
3. They are used to monitor a patient’s disease status e.g.,
serum glucose in a person with uncontrolled diabetes
Purposes of laboratory tests
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Laboratory screening criteria
1. There must be a high enough prevalence of the disease to
justify the expense.
2. Significant morbidity and mortality must be associated with the
disease if it is left untreated.
3. The disease must be detectable before symptoms surface in the
patient.
4. An effective therapy must be available that is safe and
inexpensive.
5. The test must be cost effective and easily performed in the
laboratory.
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Order of testing
1. From cheap to costly
2. From less to more risky
3. And from simple to more complex
• Within the constraints of time, risk, and cost, try to do the test
or procedure with the most efficiency as soon as possible.
• That is, use the procedure with the highest sensitivity,
specificity, and predictive values.
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Hematology
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Chemistry
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Microscopy
35 http://wwwn.cdc.gov/mpep/images/qalogo.jpg
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• 1. Appropriateness
• 2. Collection
• 3. Transport to lab
• 4. Inoculation of media
• 5. Culture and isolation
• 6. Confirmation
• 7. Report
Specimen management
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Think about the specimen before you collect it
• The specimen should be representative of the disease
process
• Prior to collecting a specimen, consider
– The risk/benefit ratio of the collection
– The amount of information to be obtained
– Test method
– Special needs of the microorganisms
• Consider geographic location, patient travel history, and
season when notifying the Micro lab of "rule-out" requests
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Questions?
• What type of specimen do you collect?
• When do you collect a specimen?
• How do you collect a specimen?
• What volume is required?
• Is there a minimum volume?
• What needs to be on the label?
• What needs to be on the requisition?
• What testing should be ordered on the specimen?
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• How do you handle the specimen?
• Is a special transport medium required?
• How do you transport the specimen?
• How do you store the specimen?
• When will you have a result?
• If you need to refer the specimen, where does it go and
when will you have a result?
• What are the limitations of this test?
• Who do you call if you have a question?
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When do you collect a specimen?
• Does the disease process require a culture?
• Collect specimens prior to administering antimicrobials
whenever possible
• Collect specimens at the acute state of illness, when the
most organisms are present
• If possible, collect specimens early in the morning
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How do you collect a specimen?
• The specimen should represent the disease process.
• Use sterile equipment and aseptic technique.
• Collect an adequate amount of specimen to perform the
testing requested
• Collect specimens in appropriate collection devices
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What needs to be on the label?
Specimen container must be labelled with the patient
name, ID number, specimen type and date and time of
collection.
An unlabelled specimen will not be processed, unless it is a
specimen which is difficult or impossible to collect again, in
which case a discussion will be had with the referring
doctor.
Patient information must be placed on the side of the
bottle.
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What needs to be on the requisition?
• Each specimen must be accompanied by a requisition slip
containing the same information as on the specimen, the
clinical diagnosis, date of onset of illness.
• The more detailed information on the requisition, the
easier it is to narrow the tests performed and to interpret
the test results.
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How do you handle the specimen?
• What tube to put it in? For example
– anticoagulant tube
– no anticoagulant tube
• How do you transport the specimen?
• Is a special transport medium
required?
– Transport immediately (within 2-4
hours) to microbiology laboratory
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Specimen rejection criteria
• Criteria for specimen rejection are dependent on individual tests.
• Generally, specimens received by the laboratory are not discarded until the physician ordering the test or responsible nursing unit is notified.
• The rejection of a specimen include
– 1. Quantity not sufficient (QNS)
– 2. Specimen too long in transit
– 3. Specimen shipped at incorrect temperature
– 4. No name on specimen
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Henry’s Clinical Diagnosis and Management
by Laboratory Methods.
23rd ed. by
McPherson RA, Pincus MR.
2017
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SCBM343
Specimen collection and interpretation
