EXERCISE 13:
SPECIMEN PROCESSING
Skills: 25 points
Objectives
1. Explain the basic use and principle of how a centrifuge works.
2. Name five (5) types of centrifuges and explain their specific uses.
3. List nine (9) general rules for the operation of the clinical centrifuge.
4. Identify two (2) important factors for proper balance of tubes in a centrifuge.
5. Explain the dangers associated with operating an imbalanced centrifuge.
6. Distinguish between whole blood, serum and plasma for testing purposes.
7. Explain how EDTA and heparin prevent blood from coagulating.
8. Define and recognize hemolysis, icterus, and lipemia and explain their effects on laboratory tests
9. State five (5) items that must be included on a tube labeled for an aliquot.
10. State the different types of plasma used in testing.
11. Define pre-analytical error and identify the phlebotomist role in preventing them.
12. List 14 reasons that a specimen would be rejected by the laboratory.
13. State the action which must be taken when a sample is rejected by the laboratory.
14. Explain the importance of verifying the blood specimen identification with the requisition slip.
15. Demonstrate proper accessioning of laboratory specimens by correctly filling in the accessioning log sheet.
16. Demonstrate appropriate specimen processing by comparing requisitions with specimens and noting any
discrepancies, problems with specimen suitability, and/or missing specimens.
17. State the resolution of any problems noted on the Specimen Accession Log.
18. Correctly label a transfer tube for serum or plasma aliquot.
19. Safely and accurately separate serum or plasma from cells using appropriate PPE.
CENTRIFUGES
Centrifuges are instruments that use centrifugal force to separate suspensions in liquids. The most frequent laboratory
use of the centrifuge is to separate the heavier cellular components of blood from the liquid serum/plasma so that it may
be used for testing.
Centrifuges vary in size, capacity, configuration and speed capability. Centrifuges that have a fixed angle head will hold
and keep the sample at an angle during the spinning process. Swinging head or swinging bucket centrifuges have a hinge
that allows the sample to swing outward. How the blood sample appears depends on whether it was spun in a fixed head
or swinging bucket type of centrifuge.
Common types of clinical laboratory centrifuges
1. Clinical centrifuge is the name given to tabletop models which can be used for urinalysis or serum separation.
These models come in either fixed head or swinging bucket configurations and usually have a speed capacity of
up to 3000 rpms (revolutions per minute). Typical clinical centrifuges are capable of holding tubes with volumes
ranging from 5 to 50 mL.
2. A serofuge is a small tabletop centrifuge primarily used in blood bank or serology to spin serological tubes.
These centrifuges can be fixed head or swinging bucket type.
3. Microcentrifuges or microfuges are powerful compact table top centrifuges becoming increasingly popular.
They are designed to spin special microtubes of 1.5 mL capacity at high speeds, usually about 12,000 rpm.
4. The microhematocrit centrifuge is a variation of the microfuge, used to spin anticoagulated blood collected in
capillary tubes in preparation for the measurement of hematocrits. Microcentrifuges are usually of the fixed head
configuration.
5. Other types of centrifuges include high-speed centrifuges which rotate at speeds up to 20,000 rpm and
ultracentrifuges which rotate at speeds over 50,000 rpm. These centrifuges are often specially equipped with
temperature control capabilities. Theses centrifuges are more commonly found in research laboratories. Highspeed/ultracentrifuges are usually of the swinging bucket configuration.
Exercise 13: Specimen Processing (revised 2/13/14)
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Operation of Centrifuges
The following are general rules; always follow manufacturer’s instructions for your instrument’s operation and
maintenance.
1. Preventive Maintenance. Centrifuges must be evaluated and undergo preventative maintenance regularly. The
routine checks of revolutions per minute using either a tachometer or a stroboscope are absolutely essential for
consistent results that meet quality control standards. The timer must also be checked against a calibrated timer
for proper results. All routine and preventive maintenance activities, as well as repairs, must be recorded in the
appropriate Quality Assurance manual.
2. ALWAYS wear gloves when handling specimens. Follow the facility protocols for wearing additional
appropriate PPE, such as disposable lab coats, protective eyewear, safety goggles, or face shields.
3. NEVER spin specimens that do not have a stopper or cap. Spinning open-top specimens creates potentially
harmful aerosols.
4. ALWAYS use tubes appropriate for centrifugation in the type of instrument you are operating.
5. NEVER operate a centrifuge on an uneven or slanted work surface. Centrifuges must be kept on a level and
firm work bench.
6. NEVER operate a centrifuge with the lid open. Do not open the centrifuge lid while the rotor is moving.
Although a ‘safety shutoff’ switch will be triggered if the centrifuge’s lid is opened, the rotor will continue to
spin until friction eventually stops it.
7. NEVER put your hands into the centrifuge until it has come to a complete stop, or try to stop it with your hand.
8. ALWAYS balance the contents of the centrifuge before operating. Running a centrifuge with an unbalanced
load could permanently damage the instrument AND poses a safety risk to you and those around you.
a. Balance each tube in terms of size and volume. For every tube placed in a centrifuge, there must be a
balance tube of identical type and must have an identical volume. For example, you would balance an
SST tube with another SST tube. Most labs have a rack of balance tubes, which consist of the various
tube used by that lab with water in them. These are used to balance the load.
b. Balance the load across the rotor head. The rotor is the part of the centrifuge which holds the tubes and
rotates during the operation of the centrifuge. Specimens that have been matched up in terms of size
and volume are placed opposite from each other across the rotor.
Exercise 13: Specimen Processing (revised 2/13/14)
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TYPES OF BLOOD SAMPLES
Whole blood is composed of all cellular elements; red blood cells (RBCs), white blood cells (WBCs), and platelets
(PLTs) suspended the liquid component, plasma. Adult blood has about 40% cellular elements and 60% liquid In tests
requiring a ‘whole blood sample’, the blood is mixed with an anticoagulant at the time of collection, kept in a mixed or
suspended state, and is NOT spun down. The most common laboratory test on a whole blood sample is the complete
blood count (CBC). Other examples of whole blood tests include the Westergren sedimentation rate (ESR), Reticulocyte
count, arterial and capillary blood gases.
Serum is the liquid expressed from clotted blood (blood drawn into a tube with no anticoagulant additive). Blood is
allowed to clot and fibrinogen, along with some of the other coagulation factors, is used up in the formation of the clot.
Serum, therefore, does not contain fibrinogen or most of the other coagulation factors. Serum is the preferred specimen
for most chemistry, blood bank and serology tests because fibrinogen, which interferes with many tests, is removed.
Plasma is the liquid present in anticoagulated blood and contains all the coagulation factors, except one. Because
plasma contains most of the clotting factors, it tends to be somewhat hazier than serum. Plasma is used for stat
chemistries and coagulation studies.
Most anticoagulants, including EDTA, act by binding or chelating calcium, a necessary component of the coagulation
process. The lack of available calcium prevents the blood from clotting.
Heparin is a naturally occurring anticoagulant which acts as an anti-thrombin. Thrombin is another essential component
of the coagulation mechanism. The effects of heparin are relatively short-lived compared to other anticoagulants. After
about 48 hours, blood drawn in heparin will begin to clot.
Exercise 13: Specimen Processing (revised 2/13/14)
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SPECIMEN PROCESSING
The following are general guide lines for processing patient specimens.
Chemistry Specimens
Serum specimens are collected in Red, Gold, Red/Black, SST, or Royal Blue with a red label. Prior to centrifugation,
these tubes must be allowed to clot completed, which usually takes 30 – 60 minutes.
Plasma specimens are collected in Green, Green/Black, PST, Tan, Brown, or Royal Blue with a green or lavender
label. These tubes may be centrifuged as soon as they arrive in the processing area.
Immunohematology (Blood Bank)
Serum specimens will be in Plain Red tubes. Plasma specimens will be Pink or Lavender tubes.
Regardless of specimen type, the tube is delivered to Immunohematology and processed by that department.
Hematology Specimens
Plasma specimens for coagulation testing are collected in Light Blue. These may be centrifuged as soon as they
arrive in the processing area.
Whole Blood specimens for hematology are collected in Lavender or Black. These specimens are never centrifuged,
but are placed on a rocker in the Hematology department to keep the specimen properly suspended.
Microbiology
Blood Cultures and any other specimen for microbiology are delivered to the department for processing.
SERUM AND PLASMA APPERANCE
Once the patient sample has been centrifuged, observe its appearance. Generally it should be clear to hazy and some
shade of pale yellow to yellow in color. Any usual color or appearance should be noted and may cause the specimen to
be rejected for testing. The following are important appearance variations you must be aware of.
1. Hemolysis – A sample is said to be ‘hemolyzed’ when the serum / plasma has a red or reddish color. Hemolysis
results when red cells rupture releasing the hemoglobin molecules. Gross hemolysis, where the serum or plasma
appears bright red, affects most lab tests and the specimen should be recollected. Some tests will be affected by even
slight hemolysis, when the serum or plasma is even slightly pink. Examples of tests that are affected by slight hemolysis
include the chemistry potassium test and enzymes LDH (lactate dehydrogenase) & AST (aspartate aminotransferase).
If you find samples that are hemolyzed, check the laboratory / departmental procedure manual to see what effect it will
have. The sample may need to be re-collected.
Hemolysis usually occurs when the venipuncture is traumatic, i.e., vein collapses, needle is moved several times, or
negative pressure causes hemolysis of the fragile red cells. In most cases it is possible to avoid hemolysis by obtaining
the blood sample with a ‘clean, non-traumatic stick’.
2. Icterus – The sample is said to be ‘icteric’ when the serum or plasma is deeply yellow, amber or even brownish due to
liver disease, damage or excessive red cell breakdown inside the body. Patients with icteric samples may have hepatitis
and are said to be jaundiced. Like hemolysis, icterus can affect many lab tests, but, unfortunately, recollection of the
specimen would not improve the serum or plasma appearance. However, appearance should be noted on the lab report "Serum icteric". In addition, icteric plasma or serum samples must be handled with extra caution because of the risks
posed by the hepatitis.
3. Lipemia – A ‘lipemic’ sample has a milky appearance to the serum or plasma. Slight milkiness may be caused when
the specimen is drawn from a non-fasting patient who has eaten a heavy meal. A heavy milky appearance occurs in rare
cases of hereditary lipemia. As with icterus, the appearance should be noted on the lab report - "Serum lipemic".
Lipemic specimens are avoided by drawing specimens from fasting patients.
Exercise 13: Specimen Processing (revised 2/13/14)
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ALIQUOTING THE SPECIMEN
After the sample has been spun down, the liquid serum / plasma must be transferred into another tube. The transfer tube
in which the aliquot of serum or plasma is placed must be labeled BEFORE the aliquot is added to the tube. The label
MUST include the following:
1. Two patient identifiers:
a. Patient name
b. Other unique identifier (Examples: date of birth, lab accession number, medical record number, etc.)
2. Date and time of collection.
3. Initials of the individual aliquoting the specimen.
4. Specimen type: EDTA plasma, citrate plasma, heparinized plasma, sodium fluoride plasma, serum, etc.
5. Special information such as trough or peak drug level.
Take great care not to put the wrong specimen in the wrong tube. One way to avoid this devastating error is to work with
only one patient specimen at a time.
Serum or Plasma Tubes WITHOUT GEL: The tube is centrifuged and the serum or plasma is carefully pipetted off into
another clean, properly labeled test tube with a clean, disposable pipette. Care must be taken not to remix plasma
specimens or contaminate either the serum or plasma with red blood cells. Red cells present in a serum or plasma
sample will alter the results of many laboratory tests.
Serum or Plasma Tubes WITH Gel: During centrifugation the gel moves above the clot to form a physical barrier
between the serum or plasma and the clot or red cell layer. The serum or plasma can then be poured off without
contamination by red blood cells.
SPECIMEN STORAGE
If the specimen is to be stored in the refrigerator or freezer, the tube should be tightly capped or tightly sealed with
Parafilm©. If the specimen is to be frozen, the ideal freezer is a true laboratory freezer which maintains constant
temperature. Regular kitchen refrigerator freezers are generally frost free and go through freeze and thaw cycles, which
may adversely affect the specimen.
ACCESSIONING SPECIMENS
Every lab has a procedure to accession specimens in the lab. Patient names and identification numbers are logged in on a
computer or on a log sheet or book along with the test(s) to be performed. This accessioning serves as a record of tests
done and is a convenient way to check if the specimen has actually arrived in the lab for testing. It is extremely important
that all patient information is correctly transcribed, that includes spelling of the patient's first and last names and the
correct identification numbers. Remember, most lab errors are clerical in nature. Examples of these types of errors
include: misspelling of the patient name, and transposing identification numbers.
Exercise 13: Specimen Processing (revised 2/13/14)
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PRE-ANALYTICAL ERROR AND SPECIMEN REJECTION
Because the goal of the laboratory is to turn out accurate results, any problem with a specimen that compromises the
quality or integrity of the results often means that the sample must often be recollected. The following is a list of some of
the reasons samples will be rejected / or will need to be recollected:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
Labeling errors:
a. Name misspelled or wrong name.
b. Identification number does not match the requisition’s number.
c. Date of collection, time of collection and/or phlebotomist’s initials are missing.
Unlabeled tubes.
Wrong tube was collected.
Patient was not fasting (when test required a fasting specimen).
Timed specimen not collected at correct time.
“Quantity not sufficient” (QNS) – specimen collected had an inadequate volume.
Specimen hemolyzed.
Anticoagulated specimen has clots in it.
Improper transport (time, temperature, light exposure).
Outdated (expired) supplies were used.
Contaminated specimens.
Stand your ground and reject improperly labeled and/or collected specimens.
Resources and References
1. Lab Manager: “6 Safety Tips for Operating a Centrifuge”.
http://www.labmanager.com/?articles.view/articleNo/1102/title/6-Safety-Tips-for-Operating-a-Centrifuge/
2. wikiHow – to do anything. “How to Use a Centrifuge”. (Be sure to watch the video.)
http://www.wikihow.com/Use-a-Centrifuge
3. “Using a Centrifuge”, Dr. Peter Darben, SPARQ-ed Coordinator, University of Queensland Diamantina
Institute. http://www.di.uq.edu.au/sparqcentrifuge
Exercise 13: Specimen Processing (revised 2/13/14)
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EXERCISE 13:
SPECIMEN PROCESSING
Procedure
1. Obtain a bag of specimens with requisitions. You should find requisition slips and tube samples for 3 different
patients.
Although not every tube in the bag will have a true blood sample within, for the purposes of this lab you will process
them as though they do.
1. Fill in the date and time columns with today’s date and the current time.
2. Compare the names and identification numbers on EACH tube with the names and identification
numbers on the requisition slip. After each tube is evaluated place upright in a test tube rack.
2. Write the patient's name and identification number in the appropriate column on your form.
a. If any errors are identified, note the problem on your "Specimen Accession Log"
b. Describe the action which must be taken to resolve the problem.
3. List each test ordered on the requisition and the tubes received in the appropriate columns. If a problem is
identified list the problem and the resolution.
a. Make sure that you have the correct specimen for each test ordered.
b. Note on the log if specimens are missing or inappropriate specimens were received.
c. Describe the action which must be taken to resolve the problem, i.e. patient must be redrawn.
4. Blue –top tubes (sodium citrate) are collected for coagulation studies (PT, PTT, etc.) It is very important that
these tubes are filled to the appropriate amount (as indicated on the side of the tube). Once in the lab, the plasma
must be efficiently harvested and separated from the cells. Often these tubes are centrifuged in the serofuge.
There will be one specimen in your bag that has a sample that will require aliquoting.
5. If a centrifuge is available in your lab you may be required to centrifuge your specimen.
a. Make sure each tube has one directly opposite from it with identical size and blood volume. If no match
is found create a balance tube.
b. Once the centrifuge is full; spin for 7 - 10 minutes.
6. Label a test tube for each specimen to be separated with the following information
a. patient's name
b. identification number or DOB
c. Specimen type (refer to procedure)
d. Date and time of collection
e. Your initials
f. Special labeling, i.e., peak, trough, etc.
7. Carefully separate the serum or plasma from the original tube into the labeled tube with a clean pipette making
sure not to contaminate the serum or plasma with red blood cells. If the red blood cells are resuspended the tube
must be respun.
8. Parafilm© or cap the top of each tube. Instructor will demonstrate this technique.
Exercise 13: Specimen Processing (revised 2/13/14)
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EXERCISE 13: SPECIMEN PROCESSING
SPECIMEN ACCESSION LOG
Name __________________________________
Date ___________________
Pts Scored__ /25
Read the instructions on the previous page CAREFULLY before beginning!!
Date
Received
Time
Received
8/5/13
1430
Patient Name
EXAMPLE
Snider, Norlyn
Patient
ID #
Test Ordered
STAT Glucose
12345
STAT
Electrolytes
Tube
Received
1 Gray
stopper
tube
Problem
*GrayTube
missing time
of collection
Resolution
* must
recollect
sample (both
tubes)
Initials
CRg
*Missing
tube for
electrolytes
Instructor Use ONLY
25 Points
1. Date and time – 0.5 each (3 total)
2. Correct spelling of name, last name first – 1 each (3 points)
3. Correct patient ID # - 1 each (3 points)
4. Lists test ordered on requisition - deduct 0.5 for each test NOT listed (1 point each patient – 3 total)
5. Tube Received – deduct 0.5 if tube is received but not recorded OR is not received but is recorded (1 point each patient – 3 total)
6. Problem – deduct 1 point if problem is present but student did not document OR 0.5 if student lists problem that is NOT a problem. (2
total)
7. Resolution – deduct 1 point if resolution of a problem is not listed (2 total)
8. Initials – (3 points)
9. Aliquot label MUST have: Name (0.5), number(0.5), specimen type (1 Point), date/time of collection(0.5) and initials (0.5) - (3 points)
Exercise 13: Specimen Processing (revised 2/13/14)
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EXERCISE 13: SPECIMEN PROCESSING
STUDY QUESTIONS
Name (PRINT): ____________________________
Date: ______________ Points:
/32
Unless otherwise noted, each question is worth one point.
1.
List 5 rules to observe when operating a centrifuge (5 points).
a.
b.
c.
d.
e.
2.
List two important items to keep in mind when balancing a centrifuge. (2 points)
a.
b.
3.
Explain the laboratory uses of the ‘serofuge’ and the ‘microhematocrit centrifuge’. (2 points)
a. Serofuge
b.
4.
Microhematocrit centrifuge
List the 3 types of specimens used for most laboratory testing AND a lab test that uses that specimen
(3 points)
a
b.
c.
5.
Compare and contrast serum and plasma. (State how they are alike and how they are different including whether or not coagulation factors are present.) (2 points).
a.
Serum
b.
Plasma
Exercise 13: Specimen Processing (revised 2/13/14)
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6.
Briefly explain the principle behind how most anticoagulants work to prevent clot formation.
7.
Explain how heparin works as an anticoagulant.
8.
Define and explain the clinical significance of each of the following terms (3 points):
a.
Hemolysis
Define:
Clinical Significance:
b.
Icterus
Define:
Clinical Significance:
c.
Lipemia
Define:
Clinical Significance:
9.
List 5 items of information which MUST be transcribed on to the tube into which an aliquot will be
placed? (2.5 points)
a.
b.
c.
d.
e.
10.
List 4 types of plasma. (2 points)
a.
b.
c.
d.
Exercise 13: Specimen Processing (revised 2/13/14)
Page 10
11.
List 3 labeling errors that would cause a specimen to be rejected by the laboratory. (1. 5 points)
a.
b.
c.
12.
List 4 non- labeling reasons that a blood specimen may be rejected by the laboratory. (2 points)
a.
b.
c.
d.
13.
What action must be taken if a discrepancy exists between the information on the laboratory specimen
and that found on the requisition slip?
14.
Why is a regular kitchen refrigerator NOT to be used to freeze clinical specimens?
15.
Why should plasma from an EDTA tube not be used for a plasma calcium level?
16. State the two methods frequently used for separating serum or plasma from the cells. (2 points)
a.
b.
Exercise 13: Specimen Processing (revised 2/13/14)
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