3 -- Understanding Lab tests
Laboratory test samples are analyzed to determine whether the results
fall within normal ranges. They also may be checked for changes from previous
tests. Normal test values are usually given as a range, rather than as a
specific number, because normal values vary from person to person. What
is normal for one person may not be normal for another person. Many factors
(including the patient’s sex, age, race, medical history, and general
health) can affect test results. Sometimes, test results are affected by
specific foods, drugs the patient is taking, and how closely the patient
follows pre-test instructions. That is why a patient may be asked not to
eat or drink for several hours before a test. It is also common for normal
ranges to vary somewhat from laboratory to laboratory.
Some laboratory tests are precise, reliable indicators of specific health
problems. Others provide more general information that simply gives doctors
clues to possible health problems. Information obtained from laboratory
tests may help doctors decide whether other tests or procedures are needed
to make a diagnosis. The information may also help the doctor develop or
revise a patient’s treatment plan. All laboratory test results must
be interpreted in the context of the overall health of the patient and are
generally used along with other exams or tests. The doctor who is familiar
with the patient’s medical history and current condition is in the
best position to explain test results and their implications. Patients are
encouraged to discuss questions or concerns about laboratory test results
with the doctor.
As you may know, lab tests are often known by many names.
For example, a Complete Blood Count is also referred to as CBC or hemogram,
among other names. The index below includes the formal test name and many
of the alternate test names used to refer to the tests. As a result, it
is a considerably longer list than the one included in the pop-down test
menu at the top of the page. If you still do not find the test you are
looking for in the list, enter the name into the Search box above, using
quotation marks if the test name is more than one word, and click SEARCH.
Start Here for Further Information:
Lab test results (NIH--Cancer)
Understanding Your Tests
Like many areas in medicine, clinical lab testing often provides few simple
answers to commonly asked questions. The issues - on topics like insurance
reimbursement and reference ranges - can be very complex. While we can't
offer the kinds of short, easy answers that we seem to be accustomed to
in this information age, we have attempted in the following articles to
break down the issues in a way that will help you to understand the issues
a bit better and perhaps to ask the appropriate questions of your doctor.
Deciphering Your Lab Report
If you've had laboratory tests performed, you may have been given a copy
of the report by the lab or your health care provider. Once you get your
report, however, it may not be easy for you to read or understand, leaving
you with more questions than answers. This article points out some of the
different sections that may be found on a typical lab report, explains some
of the information that may be found in those sections, and shows you an
example of what a lab report may look like.
Ranges and What They Mean
Test results are usually interpreted based on their relation to a reference
range. This article will help to explain what a reference range is and why
test results and references ranges should not be interpreted in a vacuum.
Approach to Medicine Improves Patient Care
Medical knowledge is accumulating—and changing—with such dizzying
speed that the medical community has found it needs new methods to cope
with it all. Evidence-based medicine (EBM) is a formalized system for helping
health professionals cope with this information explosion. This article
explains what EBM is and the role of laboratory testing in its application.
Reliable is Laboratory Testing?
Laboratory tests drive a large part of the clinical decisions our doctors
make about our health, from diagnosis through therapy and prognosis. Given
the crucial role that test data play in medical decision-making, we prepared
this article to help you understand the key concepts and practices that
are involved in making laboratory tests reliable.
Universe of Genetic Testing
An increasing number of genetic tests are becoming available as a result
of recent and rapid advances in biomedical research. It has been said
that genetic testing may revolutionize the way many diseases are diagnosed.
But genetic testing does not just help a physician diagnose disease. This
article discusses genetic testing and the different reasons genetic tests
World of Forensic Laboratory Testing
Forensic testing isn't quite like what you may see on television. This
article explains what forensic testing is, when it is necessary, and dispels
some of the misconceptions you may have about this form of laboratory
Pharmacogenomics is the study of how drugs are metabolized in the body
and the variations in the genes that produce the metabolizing enzymes.
It offers doctors the opportunity to individualize drug therapy for patients
based on their genetic make-up. This article provides specific examples
of currently available tests in this category and describes some of the
benefits and concerns with this area of laboratory testing.
As health care consumers continue to seek more convenience, particularly
among chronic sufferers and the elderly, the home testing market is growing
rapidly. Here's a glimpse at the market and the opportunities as well
as the trade offs.
Samples for Testing
Today, laboratory technologies allow testing on a wide variety of samples
collected from the human body, beyond just blood and urine. This article
provides examples of samples that can be obtained as the body naturally
eliminates them, those that are quick and easy to acquire since they reside
in the body's orifices, and some that require minor surgery and anesthesia
New Laboratory Tests into Practice
Did you ever wonder why and how new lab tests are developed? How do they
go from development to being used in medical practice? This five-part
series of articles will answer these questions and more as they describe
how different types of laboratory tests are developed, validated, and
made available for use by patients and their health care providers.
Laboratory Tests and FDA Approval
The second in the series of articles mentioned above, this discusses the
types of tests that are manufactured and sold in bulk to hospital and
reference laboratories, clinics, doctors' offices, and other health care
facilities. In the US, the development and marketing of these commercial
tests are regulated by the Food and Drug Administration (FDA), and this
article describes how these types of tests are classified.
with Test Pain, Discomfort, and Anxiety
Nobody particularly enjoys having their 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 help save or
improve the quality of your life. This series of articles has some tips
on how to approach the experience with less stress. Other titles in the
series include Tips on Blood Testing, Tips for Children, and Tips for
Staying Healthy in an Era of Patient
As health care consumers have been given more responsibility for their
care, more attention has been given to the value of preventive medicine.
This article discusses how you can take an active role in your health
care before you get sick, offering general suggestions as well as more
detail on the role of screening tests.
Preparation: Your Role
One of the most important factors in determining the accuracy and reliability
of your laboratory test is you, the patient. This brief article explains
your role in the process and ways in which you may need to prepare for
your lab tests.
Labs use a variety of methods to test the numerous analytes that are of
interest to the medical community. Understanding the method used for a
test provides a broader context for understanding your test results. This
article provides brief explanations of several common laboratory methods
mentioned on this site.