NCCN Guidelines for Patients® | Chronic Myelogenous Leukemia - page 18

18
NCCN Guidelines for Patients
®
: Chronic Myelogenous Leukemia
Version 1.2014
2.3 Lab tests
Quantitative reverse transcriptase
polymerase chain reaction
QPCR (
q
uantitative reverse transcriptase
p
olymerase
c
hain
r
eaction) is a very sensitive test that detects and
measures the
BCR-ABL
gene. QPCR makes thousands
of copies of the DNA in cells from a blood or marrow
sample to see how many cells have the
BCR-ABL
gene.
Copies of
BCR-ABL
found by QPCR are also called
BCR-ABL
transcripts. The number of
BCR-ABL
copies
detected by QPCR is called the transcript level. The
BCR-ABL
transcript level reflects the number of
BCR-
ABL
genes in your body. Changes in
BCR-ABL
levels are
measured in logs—a log reduction means the
BCR-ABL
level has decreased by a certain amount.
QPCR can detect one CML cell among more than
100,000 normal cells. This test is used to confirm
(diagnose) CML as well as to monitor the treatment
response. The QPCR test should always be done in the
same lab, preferably a lab that uses the International
Scale. The International Scale is a standardized scale
for measuring and reporting QPCR test results using a
standardized baseline level of
BCR-ABL
copies.
QPCR test results from different labs are converted
to the International Scale so that all test results are
consistent and can be compared between labs. Using
the International Scale is important because test results
from different labs can vary similar to the way currencies
in different countries vary—$1 in the United States is not
equal to €1 in Europe.
Flow cytometry
Flow cytometry looks at certain substances on the
outside surface of cells to identify the specific type of
cells present. This test is used for advanced phases
of CML to determine if the leukemia cells are mostly
myeloid or lymphoid cells. This test is important because
the cell type may affect which treatment option is best
for you. Flow cytometry can be performed on a sample
of bone marrow or peripheral blood. Bone marrow is the
soft, sponge-like tissue in the center of most bones where
blood cells are made. Peripheral blood is located outside
the bone and circulates throughout the body in veins.
BCR-ABL
gene mutation analysis
Sometimes new changes (mutations) develop in the part
of the
BCR-ABL
gene that makes the BCR-ABL protein.
These mutations change the shape of the BCR-ABL
protein, affecting how and which targeted cancer drugs
can bind to it to block the growth signals.
A mutation analysis is a test that looks for new mutations
in the
BCR-ABL
gene that may occur during treatment for
CML. This test may be performed on a peripheral blood
or bone marrow sample after months of treatment based
on how well treatment is working. Mutational analysis is
important because new or different gene mutations can
affect which treatment option is best for you.
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