26479 BCR/ABL1, Tyrosine Kinase Inhibitor Resistance, Kinase Domain Mutation Screen, Sanger Sequencing, Varies (BAKDM)

​E255K, E355G, F317L, F369V, G250E, H396R, M244V, M351T, Q252H, T315I, Y253F, Y253H, T315A, V299L, Tyrosine kinase inhibitor (TKI), Kinase domain mutation, ABL, Imatinib resistance, Chronic myeloid leukemia, Chronic myelogenous leukemia (CML), BCR-ABL1, BCR/ABL, BCR ABL, Acute lymphoblastic leukemia (ALL)

Evaluating patients with chronic myelogenous leukemia and Philadelphia chromosome positive B-cell acute lymphoblastic leukemia receiving tyrosine kinase inhibitor (TKI) therapy, who are apparently failing treatment

Preferred initial test to identify the presence of acquired BCR-ABL1 mutations associated with TKI-resistance

If BCR/ABL1 fusion type (p210, p190, p205 or p230) is not provided, BADX / BCR/ABL1, Qualitative, Diagnostic Assay will be performed at an additional charge.

In the event that no fusion form (p190, p205, p210, p230) is identified by BADX testing, BAKDM testing will be cancelled.

This is the preferred initial test to identify the presence of acquired BCR/ABL1 mutations associated with TKI-resistance.

1. Refrigerated specimens must arrive within 5 days (120 hours) of collection, and ambient specimens must arrive within 3 days (72 hours) of collection.

2. Draw and package specimen as close to shipping time as possible.

NECESSARY INFORMATION

The following information is required:

1. Patient's fusion type (p210, p190, p205 or p230)

2. Pertinent clinical history

3. Clinical or morphologic suspicion

4. Date of collection

5. Specimen source (blood or bone marrow)

This assay is comprehensive for detecting BCR/ABL1 KD mutations, but does not detect all possible mutations in ABL1; therefore, a negative result by this assay does not exclude the presence of a rare, less-well characterized, or unknown mutation that could be associated with some degree of tyrosine kinase inhibitor resistance. The clinical significance of such rarely occurring mutations is, however, uncertain.

The quantitative level of BCR/ABL1 transcript is critical for a successful assay mutation analysis, because the amplification efficiency for a longer mRNA template is decreased with a low abundance of target. If the BCR/ABL1 quantitative PCR level is too low, RT-PCR amplification of BCR/ABL1 may be unsuccessful to yield product for sequencing. Although laboratory standards are yet to be developed, a BCR-ABL1/ABL1 quantitative level above 0.1% is generally considered to be required in order to detect KD mutations by this assay.

Subclonal mutations may be difficult to identify by Sanger sequencing method, even if the BCR/ABL1 mRNA amplification was successful. This is due to the inherit sensitivity level limit of sequencing, which is typically around 15% to 20% mutant allele in a wild-type background.

EDTA blood specimens are preferred for testing. Bone marrow specimens are acceptable; there occasionally are specimen failures from bone marrow RNA, for reasons that are not completely understood. Heparin anticoagulant cannot be used because of PCR inhibition.

Assay precision does not appear to be significantly affected by specimen transport or moderate delays in processing. However, in specimens with lower levels of BCR/ABL, these conditions may cause sufficient RNA degradation to produce false-negative results. Thus, specimens should be shipped as quickly as possible. Ambient specimens over 3 days old and refrigerate specimens over 5 days old at the time of receipt are unacceptable.

​The presence of one or more point mutations in the translocated portion of the ABL1 region of the BCR/ABL1 fusion mRNA is considered a positive result, indicating tyrosine kinase inhibitor (TKI) resistance. The specific type of mutation may influence the sensitivity to a specific TKI, and could be useful in guiding therapeutic options for an individual patient.