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Diagnostic Testing
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:
UCLA School of Medicine 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: |