Diagnostic Testing
Both the
A-T Clinical Center at Johns Hopkins Hospital and the
Department of Pathology at the UCLA School of Medicine
provide laboratory tests for the differential diagnosis of A-T. A more
detailed description of these tests, including costs, is provided below.
The A-T Clinical Center at Johns Hopkins Hospital,
Baltimore, MD
The A-T Clinical Center at Johns Hopkins Hospital provides comprehensive
clinical and laboratory services for the diagnosis of A-T. Neither clinical
examination nor laboratory tests alone are sufficient to make the diagnosis
of A‑T, and we believe that the diagnosis is most accurate when laboratory
results are evaluated within the clinical context. Therefore, with rare
exceptions, the following diagnostic tests will be offered only to patients
who have been evaluated by the clinical specialists at the A-T Clinical
Center.
Cytogenetics with
G-banding (examination of chromosomes) and measurement of X-ray induced
chromosome damage.
These tests are performed in the CLIA-certified Genetics Laboratory of The
Kennedy Krieger Institute/The Johns Hopkins Hospital. The tests cost
approximately $750. Charges are covered by a grant from National Institutes
of Health for patients seen in the A-T Clinical Center.
Western blots to
detect the presence of ATM protein and ATM activity (phosphorylation of
serine 15 on p53)
These tests are performed in the CLIA-certified Pediatric Immunology
Laboratory of The Johns Hopkins Hospital. The tests cost approximately $250.
Charges are covered by a grant from the National Institutes of Health for
patients seen in the A-T Clinical Center.
Sequencing the ATM
gene to detect the specific mutations causing A-T
This test is performed in the CLIA-certified DNA Diagnostic Laboratory at
The Johns Hopkins Hospital. The test costs $4800 and takes 8-10 weeks to
complete.
For families in which
the A-T mutation is already known, carrier testing costs $400/person and
prenatal testing costs $600. These tests will be performed within 3 weeks of
receiving the specimen.
Insurance carriers
will be billed for these genetic tests, but in many cases insurance will
cover only a portion of the cost. The family will be responsible for the
unpaid balance.
Questions should
be directed to:
Dr. Howard Lederman
A-T Clinical Center
Johns Hopkins Hospital
Baltimore, MD
Phone: 800-610-5691
E-mail Dr. Howard Lederman
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UCLA School of Medicine Department of Pathology, Los
Angeles, CA
The UCLA School of
Medicine performs several laboratory tests for the differential diagnosis of
A-T. These tests are performed in a CLIA-certified laboratory within the
Department of Pathology’s Diagnostic Molecular Pathology Laboratory. The
tests must be ordered by a physician, and results will be returned to that
physician or a genetic counselor working with the physician.
Colony Survival
Assay (CSA) for radiation sensitivity
This test requires a sample of 5-10 ml heparinized blood, to arrive
within 3 days with no refrigeration. The sensitivity of the test is >99%,
with a specificity of >93% (see Sun et al., J Pediatr 2002 140:724-31). CSAs
take approximately 12 weeks to complete. Please note that when CSAs are
performed for various research protocols, the tests may take longer to
complete.
Western blot to
detect the presence of ATM protein
This test is performed using the cell line established for the CSA.
Results of the Western blot are usually ready by the time the CSA is
complete (approximately 12 weeks) and serve as additional confirmation of
the diagnosis.
A single charge of $1,065 is made for both the CSA and the Western. Most
insurance carriers will pay for this testing.
Haplotyping for
prenatal testing
This test requires a blood sample from the amnion (fetal tissue), as
well as blood samples from the previously affected child, all available
siblings, mother and father. The diagnosis of A-T for the previously
affected child must have been firmly documented by either CSA or Western
blot (preferably both), as well as by a clinical summary provided by the
referring physician. If specific ATM gene mutations are known at the time of
haplotyping, tests for these mutations are performed in parallel. It is
preferred that haplotyping be completed on the family members prior to the
mother’s pregnancy. This effectively decreases the time it takes to obtain
the results once the amniotic sample is received. The cost of haplotyping is
$750/family.
At present, carrier
testing and sequencing of the ATM gene (to determine new mutations that
cause A-T) are not performed for clinical purposes by our laboratory.
For laboratory order
forms and CPT insurance codes for CSA/Western and haplotyping, please call
310-825-7200.
Questions from physicians, genetic counselors, and clinical laboratory
directors should be directed to:
Richard A. Gatti, MD
Professor
UCLA School of Medicine
Department of Pathology
Macdonald Research Laboratories
Los Angeles, CA
Phone: 310-825-7618
E-mail Dr. Richard Gatti
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