Understanding The CD 57 Test
EVERYTHING YOU ALWAYS WANTED TO KNOW ABOUT THE CD57 TEST
By: GINGER SAVELY, RN, FNP-C
From coast to coast, frustrations abound among patients and
clinicians regarding the diagnosis of .
Misinformed health care providers in Texas and surrounding states
consider the infection rare and non-endemic. They are inclined to
rule out based on the negative result of a laboratory
test that, unbeknownst to them, is highly insensitive. In the absence
of a reliable laboratory test or adequate experience in the
recognition of the varied and complex presentations of the illness,
most clinicians are ill-equipped to diagnose chronic Lyme disease.
Many patients suffer needlessly for years, hopelessly lost in the
maze of the health care system, looking for answers and enduring the
skepticism of practitioners inexperienced with the disease’s signs
What is needed is a better Lyme test or some other objective measure
to persuade the practitioner to consider the diagnosis of chronic
Lyme disease. Enter the CD57 test! You may have heard the term “CD57”
tossed around on chat groups, or your Lyme-literate health care
provider may have even explained the test to you in one of your
moments of brain-fogged stupor. What is this number that sounds more
like a type of Heinz steak sauce than a lab test, and what in the
world does it have to do with Lyme disease?
Let’s start by going back to basic high school biology. You may
remember that (a.k.a. leukocytes) are the
components of blood that help the body fight infections and other
diseases. White blood cells can be categorized as either granulocytes
or . Mononuclear leukocytes are further sub-
grouped into monocytes and lymphocytes.
Lymphocytes, found in the blood, tissues and lymphoid organs, attack
antigens (foreign proteins) in different ways. The main lymphocyte
sub-types are B-cells, T-cells and natural killer (NK) cells. B-cells
make antibodies that are stimulated by infection or vaccination. T-
cells and NK cells, on the other hand, are the cellular aggressors in
the immune system and are our main focus in the discussion that
Let’s pause a moment and introduce something you probably never
learned about in high school biology class: CD markers. CD, which
stands for “cluster designation”, is a glycoprotein molecule on the
cell surface that acts as an identifying marker. Think of comparing
cells as comparing people. Humans are made up of innumerable
superficial identifying characteristics (such as hair color, eye
color, etc.) and so are cells. Cells probably have thousands of
different identifying markers, or CDs, expressed on their surfaces,
but 200 or so have been recognized and named so far.
Each different marker (or CD) on a cell is named with a number, which
signifies nothing more than the order in which the CD was discovered.
On any given cell there are many different cluster designation
markers (CDs), giving each cell its unique appearance and function
but also linking certain cells by their similarities (like grouping
all people with brown hair or all people with blue eyes). Cells that
have a certain kind of CD present on their surface are denoted as +
for that CD type (e.g., a cell with CD57 markers on its surface is
NK cells have their own specific surface markers. The predominant
marker is CD56. The percentage of CD56+ NK cells is often measured in
patients with chronic diseases as a marker of immune status: the
lower the CD56 level, the weaker the immune system. You may have
heard Chronic Fatigue Syndrome patients talk about their CD56 counts.
A smaller population of NK cells are CD57+.
A below-normal count has been associated with chronic Lyme disease by
the work of Drs. Raphael Stricker and Edward Winger. No one knows for
sure why CD57+ NK cells are low in Lyme disease patients, but it is
important to note that many disease states that are often confused
with chronic Lyme (MS, , ) are not
associated with low CD57+ NK counts. The good news is that for most
Lyme patients the CD57+ NK level increases as treatment progresses
and health is regained.
CD57 markers can also be expressed on other kinds of cells, including
T-cells, so it is important to distinguish between CD57+ T-cells and
CD57+ NK cells. Clinicians need to be aware that many testing
laboratories claiming to perform the CD57 test are actually looking
at CD57+ T-cells rather than CD57+ NK cells, which are the cells of
interest in chronic Lyme disease.
In order for a testing laboratory to measure the CD57+ NK level, it
first measures the percentage of lymphocytes that are CD57+ NK cells.
Then an absolute count is calculated by multiplying that percentage
by the patient’s total lymphocyte count. The standard normal range
for the absolute CD57 NK count is 60 to 360 cells per microliter of
blood. This wide range was established based upon test results of
hundreds of healthy patients. By these laboratory standards, a test
result below 60 cells per microliter would be considered below normal
and therefore associated with chronic Lyme disease. However, a recent
study of my Austin patients has led me to believe that 100 cells per
microliter is a more reliable threshold separating Lyme patients and
When Drs Stricker and Winger discovered that CD57+ NK cells are low
in chronic Lyme patients and tend to increase with patients’ clinical
improvement, an opportunity arose for Lyme-literate practitioners to
utilize a handy tool to aid in the diagnosis of chronic Lyme disease,
to follow treatment progress, and to determine treatment endpoint.
Just as AIDS patients have always held great store in their count, Lyme patients now have a fairly reliable marker of the
status of their illness.
It is important to remember that the CD57 result is just a number;
far more important is the patient’s clinical status. An old professor
of mine used to say, “treat the patient, not the lab test!” There is
still much we do not know about the CD57 marker and what other
factors may lower or raise it. However, overall, the CD57+ NK count
is a useful tool in diagnosing and treating chronic Lyme disease in
most patients. As a measure of immune status, it provides an indirect
measure of bacterial load and severity of illness. Furthermore, in a
patient who has a negative or indeterminate Lyme test but is highly
suspect for the disease, the clinician may utilize the CD57+ NK count
as one more piece in the complex puzzle of a .
Postscript: If you would like your health care provider to order the
CD57 NK test for you, your blood sample needs to be drawn into an
EDTA tube (lavender top) on Monday through Thursday and sent
immediately to either LabCorp in Burlington, NC, or Clinical
Pathology Laboratories (CPL) in Austin, TX. LabCorp and CPL are the
only two labs that perform this test properly. Quest does NOT. The
LabCorp test code is #505026 and is named HNK1 (CD57) Panel. The CPL
test code is #4886, CD57 for Lyme disease. The test is time-sensitive
and must be performed within 12 hours of collection, so blood should
not be drawn on a Friday or results may be inaccurate.