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X-linked Agammaglobulinemia (XLA): BTK (Full Gene Sequencing)
This test covers all coding nucleotides of gene BTK, plus at least two and typically 20 flanking intronic nucleotides upstream and downstream of each coding exon, covering the conserved donor and acceptor splice sites, as well as typically 20 flanking nucleotides in the 5′ and 3′ UTR.
Confirm a clinical diagnosis of XLA; detect carriers; allow early diagnosis in family members, guiding prophylactic measures
This method does not reliably detect mosaic variants; large deletions; large duplications, inversions, or other rearrangements; or deep intronic variants. It may be affected by allele-dropout, it may not allow determination of the exact numbers of T/A or microsatellite repeats, and it does not allow any conclusion as to whether two heterozygous variants are present on the same or on different chromosome copies.
Results of this test are for investigational purposes only. The performance characteristics of this assay have been determined by LabCorp. The result should not be used as a diagnostic procedure without confirmation of the diagnosis by another medically established diagnostic product or procedure.
Normal equals reference sequence or variants that are known or predicted to be benign; abnormal equals all other variants.
X-linked agammaglobulinemia (XLA), also know as Bruton's agammaglobulinemia, is a male-limited X-linked recessive immune disorder characterized by almost complete absence of mature B cells and thus the inability to produce immunoglobulins of any class. Patients experience increased susceptibility to bacterial infections and reduced ability to resolve infections with enteroviruses such as echo, coxsackie, or poliovirus, which can then lead to slowly progressing, fatal disease affecting the central nervous system. Mutations in BTK account for all XLA and about 85% of all primary defects in early B-cell development. Genetic testing can confirm a clinical diagnosis of XLA and detect mutation carriers within affected families.
Whole blood; DNA is accepted (Call 800-345-4363 for DNA collection information.)
Samples may be stored for brief periods at 4°C. Ship overnight at room temperature.
Causes for Rejection
Container broken or leaking; container not labeled or label not legible; improper anticoagulant
In cases in which a known mutation can be documented, the physician may prefer to order test 252683.
Test orders must include an attestation that the provider has the patient's informed consent for genetic testing. See sample physician office consent form: Consent for Genetic Testing. In the case of family tests (ie, known mutations), please submit the result report of the first patient tested in the family (the index case), if not performed at a LabCorp facility. Other family members are subsequently tested for the specific mutation found in the first patient tested.