COLLECTING & PROCESSING
BLOOD SPECIMEN FOR
CHEMICAL ANALYSIS
Azlin Sham bt Rambely
Mohd Fahmi Mastuki
Department of Medical Laboratory Technology
Faculty of Health Sciences
Universiti Teknologi Mara (UiTM)
Learning Outcome
At the end of this session, you should be able
to describe the:
n Specimen transport
n Separation, storage and preservation &
n Specimen rejection in the clinical laboratory
2
n
n
Collection procedure – should be
followed as outlined in the lab
procedure manual
Special care must be used when
collecting specimens from patients who
are difficult to collect from eg: children,
elderly
n
For patient with IV
line, specimen
must be collected
from different arm
@ from vessel
below IV insertion
site
Effects of specimen collection
time on chemical constituents
n
n
n
n
Chemical constituent levels may be affected
by meals, medication @ time of day
Most blood constituents do not change after
eating → blood may be collected at any time
But concentrations of constituents eg; glucose,
triglyceride & cholesterol will change after
eating
So, specimens for these tests is collected when
patients is fasting (generally in the morning
before breakfast)
n
n
n
Specimen collected from patients with
lipid metabolism disorder @ shortly after
patient has eaten may appear lipemic
Lipemic serum @ plasma → milky @
cloudy & may interfere with certain tests
Some diseases, certain blood
constituents follow patterns of ↑ @ ↓ that
make the collection time very important
n
n
Eg: creatine kinase – enzyme measured
to detect heart attack (myocardial
infarction), rises rapidly & falls back to
normal levels in the 3 to 4 days following
a heart attack
If this enzyme is not measured during this
critical period, heart attack may go
undiagnosed
n
n
Diurnal variation (changes with the time
of day), can occur with certain blood
constituents eg: iron, corticosteroids
Therefore, it is important to note the
collection time of specimen for these
tests & to consider when interpreting test
results
n
n
Some drug @ medication blood levels
will fluctuate depending on the dosage
time
Tests for therapeutic drug monitoring
must be done at set intervals before @
after administering medication
Specimen Transport
n
n
Specimens must be transported to
the lab in a timely manner
Specimen transport method is
determined by the:
- distance the specimen must be
travel &
- type of transport system available
n
n
n
n
n
n
must be collected & processed
immediately
results are expected within 1 hour of
order
some tests require centrifugation within
specified time
take to lab within 45 minutes
centrifuge within 1 hour
CLSI standard: 2 hours between
collection and centrifugation
n
n
Many hospitals have pneumatic tube
system for rapid transport of specimen
to the central lab in special leak-proof,
impact resistant containers
For another lab outside the hospital –
need couriers to transport specimen
Specimen transport within the
facility:
For nearby room @ another floor @
hospital wingn Phlebotomist @ nursing staff may
transport specimen for testing
n pneumatic tube system/capsule
pipelines
- used for transporting specimen
pneumatic tube system
pneumatic tube system
Specimen transport outside
the facility:
Courier service:
n specimen placed
in the locked box
n may need to be
processed before
transport
n must meet local
safety standard @
policy needed for
the specimen
tranportation
Specimen transport outside
the facility:
Reference labs:
n Courier service
n Shipping
n
n
specimen must be packaged in secure
containers to protect carriers from
contamination
Specimen must also be transported in
an environment that meets bio-safety
regulations & protect the quality of the
specimen
Protecting personnel:
n
n
placed specimen tubes in the biohazard bag
- for shipping
- when transporting by pneumatic tube
to open packaging or pneumatic tube
- wear appropriate PPE
- if specimen has spilled in a pneumatic
tube, follow facility policy to decontaminate
the tube
Special specimen handling:
Specimen requiring
warmth:
n testing for cold
aglutinins
n must be kept at
37° degree
celcius
Light sensitive
specimen:
n test:
- bilirubin
- beta carotene
n use amber tube
n wrap in foil
n
n
Results may be used in court or law
- blood alcohol level
- forensics specimen
- toxicology specimens
Chain of custody
- uninteruppted control of authorized
personnel
- if broken, specimen and tests are
invalid
- chain of custody form must be competed
Blood alcohol testing
n
n
n
n
Proceeding withour patient consent or court
order is considered assault & battery
Requires chain of custody
do not use alcohol to cleanse site
- do not use alcohol prep pads
- no iodine swabs
use disinfectant to cleanse site
- green surgical soap
- hydrogen peroxide
Foresic testing
n
n
n
usually for legal cases
requires chain of
custody
check specific
guidelines at your
facility
- special evidence
kits
- proper training
Toxicology specimens
n
n
reasons for toxicology specimens
- detect poisons or medications
- detect trace elements
follow facility protocol for collection, type of
specimen and equipment usage
No tourniquet/lactic acid
blood collection
n
n
n
n
n
tourniquet may be applied briefly to locate vein
remove tourniquet before collection
arm must be at rest for 2 minutes before
collection
place specimen on ice
deliver to laboratory STAT
Special coagulation studies
n
n
n
n
n
Types of studies
- factor assay
- platelet function studies
- coagulation inhibitor assays
follow strict order of of draw with large bore
needle
perform procedure quickly
invert tubes gently to mix
deliver to lab immediaetely
Separated specimen
n
n
Separation procedure
- centrifuging
. aliquoting
For most tests, separation should be
completed within 2 hours of collection
Centrifuging specimens
n
n
n
n
Separates blood
cells from liquid
components
speed & time
depend on
specimen
typical speed:1000
to 3000 rpm
typical time: 15
minutes
Using a centrifuge
n
n
n
n
n
n
balance the centrifuge
set for correct speed
close lid securely
set timer for correct
time
wear face shield when
removing tubes
open lid slowly after
centrifuge stops
completely
Aliquoting Specimens
n
n
n
take great care not to mix
up specimens
- label transfer tube
- compare to specime
tube label
use pipette to transfer
serum or plasma
store properly for delivery
to lab
n
n
mixing up
patient
specimens is
one of the
greatest
concerns of all
lab workers
mistakes can
have grave
consequences
General guidelines for
specimen transport
n
n
Tube with additives should be
inverted gently & completely 5 to 10
times immediately after being drawn
(gently inversion minimizes hemolysis)
Specimen must be properly labeledbarcode labels are becoming the
standard in most hospitals
n
An efficient &
safe way to
transport
samples is the
use of a leakproof bag
n
Tubes should be remain upright during
transport, to:
- Promotes complete clot formation when
there are no additives present
- Prevents sample contamination due to
prolonged contact with the stopper
- Reduces aerosol formation during
uncapping, as there is no residual blood
clinging to the stopper
Specimen Storage &
preservation
n
n
n
For most routine tests to be performed
within one hour, the specimen may
remain at room temp, until testing
If testing to be delayed for a few hours,
sample should be refrigerated at 4˚C
Some tests involving certain enzymes
requires specimen to be frozen
immediately after collection to prevent
the loss of enzyme activity
n
n
Most specimens may be stored in
collection tubes until testing
Certain specimen eg: bilirubin require
special handling because it is degraded
by light, so specimen should be stored in
a dark container
Problem associated with specimen
collection & processing
Hemolysis
n
n
n
Blood that is hemolyzed during collection @
processing cannot be used for most analyses
destroyed RBCs will release substances eg:
hemoglobin, enzymes (LD & AST),potassium
(K) & other intracellular components into the
serum
→ Resulting in a sample that does not
represent the patient’s true status
Hemolysis may be caused by
n overcentrifugation,
n excessive turbulance of the sample
n eg: shaking, freezing of cells, forcing
blood through the venipuncture needle,
poor venipuncture technique
Hemoconcentration
n Can occur if the tourniquet is left too
long (> 2 mins) during venipuncture
n Can cause blood stasis within the vein,
resulting in some blood constituents
being more concentrated than in
properly flowing blood
Overcentrifugation
n Blood collected to obtain serum, should
remain undisturbed for 20 – 30 mins, to
allow clotting to occur
n It is then centrifuged according to the
lab procedure manual usually for 10
mins at 1000 rpm
n Serum should be separated from the
cells as soon as possible
n
n
To obtain plasma, the anticoagulated
specimen may be centrifuged
immediately after collection
Serum & plasma must be removed from
cells before freezing, since freezing will
cause lysis
Evaporation
n
n
Specimen should remain capped until they
are tested
Evaporation will occur in uncapped
specimens, resulting in concentration of
some constituent & gas escape @
exchange, which may alter other values eg:
pH, bicarbonate (HCO3-) concentration
Microbial contamination
n
n
n
Clean pipets @ pipets tips should be
used to transfer each sample
If reusable sample cups are used, they
must be clean & dry to avoid
contaminating @ diluting of samples
Bacterial contamination of specimens
must be avoided
Chemical contamination
n
n
When multiple blood samples are
obtained with a vacuum collection
system, the “order of draw” is important
Tubes for serum collection must be filled
before those containing anticoagulant
Specimen rejection
n
n
All specimen received by the lab
must be evaluated for acceptability
before further processing
specimen rejection may be due to
improper collection techniques or
handling or processing errors
Pre-examination error:
n Error that occur before, during or
after blood collection
- patient identification errors
- specimen collection errors
- specimen handling errors
Specimen rejection
n
n
re-collection may be required if
abnormalities are detected
accurate test results depend on
specimen quality
- errors may go unnoticed
- questionable results otained
Criteria for rejection
Hemolysis:
n destruction of red
blood cell
n can result from
improper
collection or
handling
Clotted anticoagulated
specimens
n some tests require
unclotted specimens
n blood may clot even in
tubes that contain
anticoagulant
n often due to collection
issues
Incomplete
collection/insufficient
volume for testing:
n may be rejected as
“quantity not
sufficient”
n causes improper
/inadequate
additive-to-blood
ratio
n
n
n
n
incorrect tube collected eg: EDTA for a chemistry
test
incorrect draw order
hemoconcentration
- not easily detected
icterus
- dark-yellow to greenish
color
- caused by bilirubin
n
n
Lipemia
- cloudy plasma
- caused by abnormal
amount of fats
Special requirements not
followed/Improper special
handling
- eg: cold agglutinins not kept
warm
Specimen rejection
n
n
n
n
n
n
No requisition form
Improper @ inadequate identification
Unlabeled @ mislabeled specimen
Tubes past their expiration date
Specimen drawn at the wrong time
Contaminated specimen (eg: urine for
C&S testing collected in a nonsterile
container