Most routine laboratory tests require a
blood sample. Common
as it is, this brief
procedure is the
test people tend to
have the most
worries about.
There are two main
problems really: 1)
the physical one,
enduring the needle
and 2) the emotional
one, seeing your
blood being removed.
For most people,
having your blood
taken is not a
problem, just a
minor inconvenience.
Others feel anxious
and need some
strategies to help
them cope. For a
much smaller number
of individuals, the
physical condition
of their veins makes
the procedure
harder, for example
their veins are sore
from intravenous
(IV) therapy,
scarred from
frequent
venipunctures, or
just hard to find
and use.
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Common Tests
Today's technologies
allow testing on an
impressively wide
variety of samples
collected from the
human body. Most
often, all that is
required is a blood
sample. Samples of
urine, saliva,
sputum, faeces,
semen, hair and
other bodily fluids
and tissues also can
be tested.
Some samples can be
obtained as the body
naturally excretes
them. Others are
quick and easy to
acquire because they
reside in the body’s
orifices. For some,
minor surgery and
anaesthesia give the
doctor access to the
required sample.
Samples That Are Naturally Eliminated
You can collect some
samples such as
urine, faeces,
sputum, and semen in
private, without
involving a health
care worker; elderly
and paediatric
patients may,
however, require
assistance. Usually,
collecting these
samples is painless
because they are
collected as the
body naturally
excretes them. There
are also no after
effects. Obtaining
these samples can,
however, be awkward
and
unpleasant because
they involve
elimination of
bodily wastes or
bodily fluids and
involve body parts
and functions people
prefer to keep
private.
The body samples
listed below can be
collected without
involving a health
care provider.
Semen — Male
patients ejaculate
into a specimen
container, which
some men find
embarrassing or
difficult. Usually,
men need to refrain
from ejaculating for
3 to 4 days before
collecting the
specimen. The
specimen must be
kept warm and
brought to the lab
within the time
period specified. It
is important that
you follow the
instructions
provided for the
specific test.
Sputum —
Patients are
instructed to cough
up sputum from as
far down in the
lungs as possible.
(A nurse may assist
the patient in some
situations.) You
should follow the
instructions
provided to ensure
proper collection.
Stool —
Patients usually
collect this sample
themselves whilst
using the toilet,
following
instructions to
prevent the sample
from becoming
contaminated from
other material in
the toilet bowl.
Patients may also be
told to avoid
certain foods during
the test period.
Depending on the
test, patients may
be instructed to
collect the sample
in a container,
scoop a small
portion into a vial,
or smear a small
amount on special
test paper. Wash
your hands well
after handling the
sample.
Urine — Most
urine specimens are
collected by having
the patient urinate
into a container or
receptacle. To keep
the sample from
becoming
contaminated by
materials outside
the urinary tract,
patients are given
instructions on how
to clean the area
and pass a bit of
urine before
collecting the
specimen in the
container. (If a
urinary catheter is
required, a health
care worker is
usually responsible
for insertion.
Because catheters
increase the risk of
infection, you will
receive instructions
to ensure meticulous
hygiene and sterile
technique).
Collecting the urine
specimen is awkward,
but not in itself
uncomfortable (an
infection, however,
can create a burning
sensation during
urination). For
certain tests,
samples are
collected at home,
possibly over a
period of hours, and
will need to be
refrigerated.
Remember to wash
hands well after
collecting the
specimen.
Samples That Are
Easy to Reach
Some samples are
collected by simply
running a swab over
the affected area.
Procedures of this
type can be
performed at the
point of care (in a
clinic, in your
doctor's surgery, or
at the hospital
bedside). The sample
may then be sent to
a laboratory for
analysis
(alternatively a few
tests provide
bed-side results in
just a few minutes).
Throat, nasal,
vaginal, and wound
cultures, for
example, are
obtained in this
way. The procedures,
while they may be
uncomfortable, are
generally quick and
painless and have no
after-effects.
Secretions and
Tissues from the
Female Reproductive
System—Samples
of vaginal
secretions are
obtained by running
a cotton swab over
the walls of the
vagina; cervical
cells for a smear
test are obtained
using a cotton swab
and spatula (called
a speculum) or a
tiny brush. Both
procedures are
painless.
Endometrial tissue
samples are obtained
by inserting a thin,
flexible hollow tube
into the uterus,
during which you may
feel a slight pinch
or brief cramping.
Patients may feel
embarrassed or
vulnerable because
of how these samples
are collected. Some
patients find the
position of the legs
uncomfortable, some
complain that the
stirrups and
speculum are cold,
and some feel slight
pressure as the
speculum is
inserted. A
sensitive approach
by the health care
professional
contributes greatly
to the patient’s
emotional comfort.
If you are
physically
uncomfortable, try
asking for what you
need (such as
a smaller speculum).
Also, if you would
be more at ease if a
woman performs these
procedures or if a
female health worker
is in the room when
the procedure is
performed, ask your
practitioner to
provide these
modifications.
Various Cultures
(Nasal, Throat
Cultures, Wound)—The
specimen is
collected by running
a swab over the area
of interest. People
typically respond to
swabbing of their
throat with a
momentary "gag"
reflex. If the
throat is sore, the
sample collection,
brief as it is, can
be uncomfortable.
Similarly, a nasal
swab may be a bit
uncomfortable as the
swab is inserted and
reaches areas inside
the nose that are
typically never
touched. Try to
remember that the
discomfort is
temporary and ask
your practitioner if
there are ways to
minimize any
soreness that may
result. You may also
find it helpful to
perform relaxation
techniques before,
during, or after the
procedure.
Samples From Within
Some samples can only be
obtained by breaking
through the body’s
protective coverings
(e.g., skin). Blood
samples and tissue
specimens, for example,
are obtained in
minimally invasive
procedures conducted by
specially trained
doctors, nurses, and
medical personnel.
Blood—Blood
samples can be collected
from the capillaries and
veins by a trained
phlebotomist; arterial
blood samples are drawn
by a specially trained
nurse or doctor. The
sample is obtained by
needle puncture and
withdrawn by suction
through the needle into
a special collection
tube. The procedure
usually takes just 3
minutes and hurts just a
bit, typically when the
needle is inserted or
withdrawn.
Minor Surgical
Procedures—Samples
of bodily tissue, spinal
fluid, and bone marrow
can be collected in
minor surgical
procedures conducted by
doctors and nurses who
have had specialised
training. A local or
general anaesthetic is
used, depending on the
procedure, so the
patient remains
comfortable. These kinds
of tests are requested
only when there is
evidence of a problem.
Your doctor and the
medical staff will
usually devote more time
to explaining these
procedures and why they
are needed.
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Reference Ranges & What
They Mean
-
For most tests, the
reference ranges are
specific to the
laboratory that
produces the test
results. Different
laboratories use
different kinds of
equipment and
different kinds of
testing methods.
That means they have
to establish their
own ranges, and will
provide your test
result with an
accompanying
reference range
appropriate to the
laboratory. The
doctor should
therefore apply the
reference range
supplied by the
laboratory which
performed the test
rather than that
used by another lab
or one given in a
book.
-
We want you to be
informed, but we can
not pretend to take
the place of
communication with
your doctor. We want
you to understand
what the test is,
and how it can be
used but because we
can't be aware of
all the factors that
could affect your
test results, we
can't interpret the
results. If you need
further explanation
of your results, you
should talk to your
doctor.
What is a Reference
Range?
The interpretation of
any clinical laboratory
test involves comparing
the patient's results
with the test's
"reference range".
The first step in
determining a reference
range is to define the
population to which the
range will apply. A
large number of
individuals from a group
who are thought to
represent a "normal"
population, would be
tested for a particular
laboratory test. The
reference range is then
derived mathematically
by taking the average
value for the group and
allowing for natural
variation around that
value (plus or minus 2
standard deviations of
the average). In this
way, ranges quoted by
labs will represent the
values found in 95% of
individuals in the
chosen ‘reference’
group. In other words,
even in a "normal"
population, a test
result will lie outside
the reference range in
5% of cases (1 in 20).
This is why the term
"reference range" is
preferred over "normal
range".
When you examine test
results from different
populations, you quickly
discover that what is
"normal" for one group
is not necessarily
normal for another
group. Indeed for tests
such as cholesterol the
idea of a normal range
has been replaced to a
large extent by use of
target values, achieved
either by lifestyle
changes or active
treatment.
Whether your test result
is within the laboratory
reference range or not,
it must be considered
within the context of
your personal
circumstances, and with
the benefit of your
doctor's knowledge of
your past medical
history and the results
of any other
investigations
performed.
Effects of Age and Sex
For many tests, there is no
single reference range that
applies to everyone because
the tests performed may be
affected by the age and sex
of the patient, as well as
many other considerations.
For example alkaline
phosphatase is an enzyme
found in the cells that make
bone, so its concentration
in the body rises in
proportion to new bone cell
production. In a child or
adolescent, a high alkaline
phosphatase level is not
only normal but desirable
because the child should be
growing healthy bones. But
these same levels found in
an adult are a sign of
trouble. So experience from
testing large numbers of
people has led to different
reference ranges for
different age groups.
The patient’s sex is another
important consideration for
some tests for example,
muscles contain an enzyme
called creatine kinase.
Because of their larger
muscle mass, men tend to
have higher CK levels in
their bloodstream than
women.
Other Factors
Affecting Test Results
A plethora of additional
factors can affect your
test results: the time
of day you have your
blood sample taken, your
intake of caffeine,
tobacco, alcohol, and
vitamin C; your diet
(vegetarian vs. meat
eaters); stress or
anxiety; or a pregnancy.
Even your posture when
the sample is taken can
affect some results, as
can recent heavy
exertion. For example,
albumin and calcium
levels can increase a
little when moving from
lying down to an upright
position. Vigorous
exercise can affect
levels of creatine
kinase (CK), aspartate
aminotransferase (AST),
and lactate
dehydrogenase (LDH).
All these considerations
show the significance of
taking blood or urine
samples in a
standardised fashion for
performing and
interpreting laboratory
tests. It’s important to
follow your doctor’s
instructions when
preparing for your
tests, such as coming in
first thing in the
morning and getting your
blood taken before you
eat anything.
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Common Misconceptions
There are two main
misconceptions about test
results and reference
ranges:
Myth: "An abnormal
test result is a sign of a
real problem."
Truth: A test result
outside the reference range
may or may not indicate a
problem—the only sure signal
it sends is that your doctor
should investigate it
further. You can have an
abnormal value and have
nothing wrong—but your
doctor should try to
determine the cause.
It’s possible that you fall
in that 5% of healthy
people who fall outside the
reference range. In
addition, there are many
things that can give a
misleading result without
indicating a major problem.
A high blood sugar could be
diet-related rather than
caused by diabetes. A lipid
result could be high because
you didn’t fast before the
test. If your doctor is
unsure about the test result
they may wish to repeat it.
Some abnormal results may
disappear on their own,
especially if they are on
the border of the reference
range.
Myth: "If all my test
results are normal, I have
nothing to worry about."
Truth: It’s certainly
a good sign, but it’s only
one set of tests, not a
guarantee. There is a large
overlap among results from
healthy people and those
with diseases, so there is
still a chance that there is
an undetected problem. Just
as some healthy people’s
results fall outside the
reference range, lab test
results in some people with
disease fall within the
reference range.
If you’re trying to follow a
healthy lifestyle, take it
as a good sign, and keep it
up. But if you’re engaging
in high-risk behaviour, such
as drug and alcohol abuse or
a poor diet, it only means
"so far so good," and the
potential consequences
haven’t caught up with you
yet. A good test result is
not a license for an
unhealthy lifestyle.
If you previously had
abnormal results, normal
results certainly provide
good news. But your doctor
may want to conduct
follow-up tests some months
later to make sure you’re
still on track and to follow
any trends.
How Reliable is
Laboratory Testing?
For many people,
laboratory testing is an
invisible side of
medical care. However
the decisions your
doctor makes about your
health status -
diagnosing the cause of
symptoms, developing a
course of action and a
treatment plan,
monitoring your body's
response to therapy -
can be made with greater
confidence when lab
results are available to
shed light on what is
happening inside you.
Given the crucial role
that test results play
in medical
decision-making, we
thought it worthwhile to
discuss some of the key
concepts and practices
that are involved in
making laboratory tests
reliable.
A test's reliability is
monitored through
rigorous quality
standards and controls
practiced by the lab.
Your doctor acts as the
final security
checkpoint, considering
the findings from your
lab report in light of
other information about
your condition. These
steps ensure that the
lab tests critical to
high-quality health care
can be used with great
confidence.
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Coping with Test
Pain, Discomfort,
and Anxiety
Nobody particularly
enjoys having blood
drawn or providing a
urine or stool
sample, but a
medical test
conducted on a small
sample collected
from your body can
give your doctor
information that can
improve the quality
of your life or even
save it. If
undergoing medical
tests makes you or
someone you care for
anxious,
embarrassed, or even
difficult to manage,
read this article
for some general
tips on how to make
the sample
collection
experience more
positive and less
stressful.
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Home Testing
Home testing offers many
benefits - convenience,
privacy, control, but
it's also important to
recognize the potential
tradeoffs between
quality and convenience
and take steps to
protect yourself against
unapproved tests, the
possibility of false
results, and your own
lack of training.
In the laboratory or at
the bedside, for
example, nurses, and
biomedical scientists
must undergo training in
the testing procedure,
and the instrumentation
used to perform the test
is properly maintained,
and quality monitored.
Home tests can be used
to screen for, diagnose,
or monitor disease. Many
home tests are available
over the counter (OTC)
in local supermarkets or
pharmacies or directly
from manufacturers by
Internet, phone, or mail
order.
Examples of these
include:
-
cholesterol, for
assessing risk of
heart disease;
-
glucose, for
monitoring diabetes;
-
drugs to test for
the presence of
illegal drugs and
drugs of abuse;
-
hCG, to screen for
pregnancy;
-
faecal occult blood,
to screen for bowel
cancer; and
-
luteinising hormone
(LH), to predict
ovulation
Some home tests, like
those for pregnancy,
produce immediate
results. Others are sold
as collection devices -
you use the device to
collect a specimen (for
example, urine or stool)
and then mail the device
containing the sample to
the laboratory for
evaluation. Although
home tests are
convenient, they may not
be the last word in
diagnosis or monitoring.
Errors can arise because
of how you collect the
sample, the time of day
you collect it, how
precisely you time the
test, or the impact of
medications you may be
taking. Yet these tests,
especially those
designed to monitor
diseases like diabetes,
are important to your
quality of life if you
live with chronic
illness. Home glucose
testing, for example,
allows you to monitor
your blood sugar level
and adjust diet or
medication accordingly.
It is important that you
take steps to make sure
the home tests you use
give reliable results.
Quick Guide
Home testing offers a way
for you to test for medical
conditions in the privacy of
your own home and to monitor
chronic health conditions.
If you use home tests,
however, protect yourself
against the possibility of
unapproved tests, false
results, and your own lack
of training by following
this guidance.
Make sure that the test you
are purchasing bears a CE
mark. The European Union and
the UK regulatory
authorities require
manufacturers to meet
stringent controls.
Check the expiration date.
Do not buy tests if they
have expired. The chemicals
in the test may have lost
their effectiveness, and the
results may not be valid.
Follow the package
directions on where and how
to store the test. Don't
leave temperature-sensitive
tests in conditions that
don't meet storage
requirements.
Note and follow any special
precautions before
performing the test. For
example, check to see when
the test is to be performed
(morning, evening), or under
what conditions (fasting, no
physical exertion, etc.).
Perform the test EXACTLY as
instructed. If you have
questions or are at all
unsure about how to use the
test, consider talking to
your doctor.
Make sure you understand the
meaning of the test results,
and what to do about them.
If you do not, talk to your
doctor.
Consult the following
agencies for additional
information. These are
general links that will
require additional searching
for relevant information.
-
Medicine and Health care
products Regulatory
Agency (MHRA)
-
UK agency with website
containing information
on home tests (in vitro
diagnostics).
-
National Electronic
Library for Health
-
Searchable database of
medical information.
-
BBC Health
-
Searchable website.
-
American Society for
Clinical Laboratory
Science (ASCLS)
-
This US site has useful
information for
patients.
-
Center for Devices and
Radiological Health (CDRH)
-
USA medical device
approvals. Daily updates
available. Searchable.
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