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Chapter 5
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Specimen Processing
Chapter 5
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Objectives
Upon completion of this chapter, you should be able to:
• List requirements for special specimen handling
procedures.
• Describe the technique required for collecting
blood cultures.
• List the steps for Unopette® collection.
• Describe the procedure for performing a
microhematocrit.
Chapter 5
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Objectives cont’d
• Explain the collection process and procedure for
making a peripheral blood smear.
• Discuss common point-of-care and CLIA waived
tests.
• Explain the procedure for urine specimen
collection and reagent testing.
• Identify safety requirements for operating a
centrifuge.
Chapter 5
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Special Handling Procedures
In addition to blood collection, some specimens require
special handling either before or after the blood is
collected.
Common Tests Requiring Special Handling Procedures
Blood
Cultures
Legal Specimens
Cold Agglutinins
Chilled and
Light-Sensitive
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Blood Cultures
• Requested on patients
with a high fever
• Purpose is to isolate
microorganisms from the
patient’s blood that may
be causing the fever
• Strict aseptic technique
is required for the
Blood culture bottles
collection of the blood
are larger than normal
specimen
venipuncture tubes
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Blood Cultures Part 2
• Blood culture bottles
contain culture media,
which enhances the
growth of the
microorganisms
• Blood cultures are
usually ordered STAT
• Collected in sets of two
or three
• Septicemia is the presence
of microorganisms in the
blood with symptoms that
can result in death
• Each set is collected
from different sites at
different time intervals
One sample will be incubated as an anaerobic specimen and
the other as an aerobic specimen
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Blood Cultures Part 3
• Blood cultures seek to identify
the agent(s) responsible for
the patient’s illness
Common Pathogen Classifications
• Bacteria
• Protozoa
• Fungi
• Viruses
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Blood Culture Volume
Blood Culture Volume
• The exact amount indicated by the
manufacturer must be collected.
• Usually 8 to 10 mL per bottle or tube is
sufficient for an adult. Lesser amounts are
drawn on infants and children.
• The correct amount is needed to increase
the chance of bacterial growth.
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Blood Cultures Part 4
The collection of blood cultures is essentially the same as for
routine venipuncture, except:
• Special site
cleansing
• Specimen transfer
• Amount of
blood needed
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Site Cleaning Procedure
Blood Culture Site Cleaning Procedure
Correct cleaning of the site is the most
important part of collecting blood cultures
Steps to Correct Cleaning
1. Release the tourniquet after
site is selected
2. Clean first with 70% to 95% alcohol, chlorhexidine
gluconate, or benzalkonium chloride using
concentric circles, from the center working
outward
3. Do not allow the strokes to go back toward the
center area
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Site Cleaning Procedure Cont’d
Steps to Correct Cleaning (cont’d)
4. Allow the site to air dry
5. Repeat cleansing using a 2% iodine
swab or applicator if using alcohol
6. Allow iodine to dry and do not retouch
the area
If the patient is allergic to iodine, use another
cleanser.
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Blood Culture Specimen
Transfer
Collecting Blood Culture Specimens
• If using a syringe, be sure to have a syringe that can
hold at least 20 mL. Attach the syringe to a transfer
device and fill anaerobic bottles first.
If a butterfly setup is used, the aerobic sample is drawn first so
that air from the butterfly tubing is cleared before the
anaerobic culture sample is drawn.
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• Establishing a chain of custody is required for
medicolegal issues. Without proper proof of custody,
the specimen will be considered invalid.
• A chain of custody form must be completed
correctly, and multiple copies are used as a safeguard
system.
These specimens must be correctly identified and under
the uninterrupted control of authorized personnel to
ensure their validity.
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Cold Agglutinins
• Testing for cold agglutinins or antibodies
is done for patients suspected of having
atypical pneumonia.
• Atypical pneumonia is caused by the
microorganism Mycoplasma
pneumoniae.
• People infected with Mycoplasma
pneumoniae produce autoantibodies.
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Cold Agglutinins Part 2
Normal body temperatures range from 97.6F to 99.6F. At
temperatures lower than normal body temperature, cold
agglutinins attach to red blood cells and cause clumping.
Specimen Collection
• Use red-topped tubes
that do not contain
additives
• Collection tubes must be
prewarmed
• Keep the sample at
98.6F until the serum
can be separated from
the cells
• Serum must be separated
from cells within 1 hour
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• Some specimens must be chilled or covered
immediately after collecting.
Chilled Specimens
Light-Sensitive
Specimens
•Arterial blood gases
•Bilirubin
•Ammonia
•Lactic acid
Chapter 5
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Apply Your Knowledge Part 2
Which of the following best describes the correct
cleansing procedure for blood culture collection?
A. Clean the arm starting a distance from the site and clean
toward the selected site
B. Use linear strokes to clean up and down the arm until the
entire arm is cleansed
C. Clean the site starting in the center and working outward
Answer: C. Clean the site starting in the
center and working outward
Chapter 5
GREAT!
18
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Apply Your Knowledge Part 3
James is suspected of having atypical pneumonia.
Which of the following tests will most likely be ordered?
A. Arterial blood gases
BRAVO!
B. Cold agglutinin
C. Bilirubin
Answer: B. Cold agglutinin tests for atypical pneumonia
caused by Mycoplasma pneumoniae
Chapter 5
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Unopette Procedure
A Unopette®, manufactured by Becton-Dickinson, is
a prepackaged microcollection device.
• Disposable
• Consists of a plastic reservoir containing a
premeasured volume of reagent
Common Tests Performed with a Unopette
• White blood cell count
• Red blood cell count
• RBC fragility
Chapter 5
• Platelet count
• Hemoglobin
20
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Unopette Procedure Part 2
Each test requires a specific Unopette that has a
different premeasured volume of reagent inside.
• Specific pipettes accompany each Unopette.
• Pipettes are self-filling, thin-walled, glass capillary
tubes attached to a plastic holder.
• Use a dermal puncture specimen to fill the pipette.
• Wipe the pipette after it fills with blood, but do
not touch the end of the pipette with gauze.
• Gently invert to mix the sample with the reagent.
• Label Unopette and transport to lab.
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Apply Your Knowledge
Which tests can be performed with the
Unopette microcollection device?
ANSWER: WBC count, RBC count, RBC
fragility, platelet count and hemoglobin
Good Job!
Chapter 5
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Measuring Microhematocrit
• Microhematocrit tubes are used
for measuring hematocrit or
packed cell volume
• They have a thin red band
around the end of the tube
• These tubes are coated with
sodium heparin
• Blood flows freely into these
tubes because of capillary
action
Chapter 5
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Measuring Microhematocrit Part
• Fill two capillary tubes 3/4 full
2
• Seal the end that was not used
to collect the specimen by
embedding the clean end into a
clay sealant (if the tube
requires it)
• Place in a separate tube for
labeling and transporting to the
laboratory
• Place in centrifuge machine
according to procedure
NOTE: The values of the two microhematocrits should
match within 2 percent.
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Apply Your Knowledge Part 6
True or False: Microhematocrit tubes are coated with
an anticoagulant.
Hey, remember! An
anticoagulant prevents
blood from clotting.
Great!
Answer: True
Chapter 5
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Peripheral Blood Smear
A blood smear is for the microscopic examination of blood.
• Venous or capillary blood may be
used to prepare a blood smear.
• The complete blood count (CBC)
differential test is done with a blood
smear.
• Blood smears are also used to
diagnose malaria, anemia, and
leukemia.
Chapter 5
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Peripheral Blood Smear Part 2
Blood Smear Procedure
• Fresh drops of blood are
obtained, usually following
dermal puncture
• Wipe away the first drop of
blood
• Place 1 drop of blood about
1/2 inch from the frosted
end of one glass slide
• Hold the spreader slide at a
30 to 35o angle and spread
blood toward the opposite
end of the slide
• The blood smear should
be smooth in appearance
with no irregularities,
streaks, or holes and a
feathered edge
• The wedge method is the
most common technique
for making blood smears
Chapter 5
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Apply Your Knowledge
Blood smears are used to diagnose which of
the following diseases?
A.
B.
C.
D.
E.
Malaria
Leukemia
Anemia
All of the above
None of the above
Bravo!
ANSWER: D. All of the above
Chapter 5
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Point-of-Care Testing
• Near-patient testing
• Designed to reduce hospital cost and reduce
turnaround time for blood test results
• Instruments are portable, internally calibrated, and
easy to use
• Point-of-Care testing (POCT) is usually performed by
phlebotomists, nurses, technicians, or medical
assistants
• Dermal puncture usually done because a small blood
specimen is needed
• Each instrument must be calibrated and requires
quality control checks
Chapter 5
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Point-of-Care Testing Part 2
• Bicarbonate
• Ionized calcium
Common Point-of-Care Tests
• Cholesterol
• Glucose
• Blood ketones
• Hemoglobin
• Urine dipstick
• Sodium
• PT and PTT
• Potassium
• Chloride
Chapter 5
• Blood gases
30
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• Often requires blood from a dermal
puncture.
• POCT is done at various facilities.
• If a clinical lab is not available, only
CLIA waived testing can be performed.
• CLIA waived tests are those that are
cleared for home use.
Chapter 5
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Before the Test
• Confirm test orders
• Establish a procedure for patient ID
• Give patient pre-test instructions
• Collect specimens according to package
directions
• Label specimens appropriately
• Never use expired kits
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During the Test
• Perform quality control testing
• Correct any problems
• Establish a policy for frequency of control
testing
• Carefully follow all test-timing
recommendations
• Interpret test results using product inserts as
a guide
• Record test results according to office policy
Chapter 5
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After the Test
• Report results in a timely manner
• Follow package insert for follow-up
• Follow OSHA regulations for disposing of
biohazardous waste
• Participate in quality assurance assessment
programs
Chapter 5
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Apply Your Knowledge Part 7
Which of the following tests cannot be performed
with POCT?
A. Glucose
B. Hemoglobin
Good Job!
C. Blood culture
D. Cholesterol
Answer: C. Blood cultures require a larger amount of blood
and have to grow in culture media.
Chapter 5
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• Used to evaluated substances found in
urine
• Consist of the physical component,
chemical component, and the
microscopic component
• First morning urine is best used for
testing
• Chain of custody must be established
for drug and alcohol testing
• Should be refrigerated if not tested
within 1 hour
Chapter 5
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Obtaining Urine Specimens
• For a Female:
• Separate the skin folds and wipe front to
back three times
• Keep the skin folds apart and collect a
midstream urine in the cup
• Once ¾ full, place the lid on the cup
• Label the specimen
• For a Male:
• Use 2 towelettes to clean the head of the penis
• If uncircumcised, keep foreskin retracted while patient urinates
and collect a midstream urine in the cup
• Once ¾ full, place the lid on the cup
• Label the specimen
Chapter 5
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Urine Specimen Testing
The Urine Dipstick
• Uses reagent strips to test urine for a number of substances
• Keep strips in a cool dry area
• Never remove them from the container until ready to test
• Examine the strips for discoloration
• Check the expiration date
• Always run a control sample when opening a new supply
• Write the date opened
Follow the manufacturer’s directions for accurate results
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Apply Your Knowledge
Which is the best urine specimen for testing?
ANSWER: The first morning urine
GREAT!
Chapter 5
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Centrifuge Operation
Centrifuging is the spinning down or separating of cells from
the liquid portion of the blood.
• Specimens also require aliquoting (dividing specimens
into separate containers)
• Aliquoting for most laboratory tests requiring serum or
plasma must be done within two hours or less
What happens if
the specimen is
not separated in
time?
• Test results could be altered
• If the RBCs are left in contact
with the serum, the glucose
level would be decreased
Chapter 5
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Centrifuge
Operation
Part
2
Types of Centrifuges
• Refrigerated
• Floor models
• Tabletop models
The speed of rotation
and the radius of the
rotor head determine the
relative centrifugal force
of a centrifuge, which is
expressed in gravity (g).
Most laboratory specimens are
centrifuged at 750 to 1000 g for
15 minutes
Chapter 5
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Centrifuge Operation Part 3
• Place tubes of equal
size and volume
directly across from
each other so the
machine will be
balanced
After centrifugation, always
be sure the transfer tube is
properly labeled before you
begin to aliquot a specimen
Chapter 5
• Never open the lid
until the centrifuge
machine has come to
a complete stop
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Apply Your Knowledge
Within what time frame should specimens be
centrifuged for tests that require serum or
plasma?
ANSWER: Within 2 hours
GREAT!
Chapter 5
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CHAPTER SUMMARY
• Specimens may require special handling or
collection in order to be accurate.
• Blood cultures must be drawn under strict
aseptic technique to prevent false results.
• When using a Unopette, collect the specimen
with the pipette and mix the specimen carefully.
• To perform a microhematocrit, obtain blood in a
capillary tube and centrifuge. The separated
cells can be used to determine the patient’s
hematocrit.
Chapter 5
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CHAPTER SUMMARY (cont’d)
• Peripheral blood smears require a drop of blood
on a slide. The blood is spread across the slide
using a spreader slide.
• Point-of-care tests are obtained and tested
immediately at the point of care or near the
patient. CLIA waived tests pose a minimal risk to
the patient.
• A urine specimen can be collected and a
reagent strip may be used to determine the
concentration of a substance.
• When using a centrifuge, make sure the load is
balanced.
Chapter 5
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END OF CHAPTER 5
Choose a job you love and you will
never have to work a day in your life.
-- Confucius
Chapter 5
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