CPT® Code 81170

ABL1 (ABL proto-oncogene 1, non-receptor tyrosine kinase) (eg, acquired imatinib tyrosine kinase inhibitor resistance), gene analysis, variants in the kinase domain

The CPT® Code 81170 pertains to the molecular genetic testing of the ABL1 gene, specifically focusing on the analysis of variants within the kinase domain. The ABL1 gene is located on the q arm of chromosome 9 at position 34.1 and encodes a protein that functions as a non-receptor tyrosine kinase. This protein plays a critical role in various cellular processes, including cell division, adhesion, differentiation, and the cellular response to stress. In the context of certain hematological malignancies, such as chronic myelogenous leukemia (CML) and acute lymphoblastic leukemia (ALL), patients may develop resistance to tyrosine kinase inhibitors (TKIs) like imatinib. This resistance is characterized by the loss of a previously effective response to the treatment. TKIs work by binding to the inactive form of the ABL kinase, thereby inhibiting its activity at the ATP-binding site, known as the P-loop, of the BCR-ABL fusion protein. This inhibition prevents the autophosphorylation of the kinase, maintaining the BCR-ABL tyrosine kinase in an enzymatically inactive state. However, the emergence of at least 40 known mutations associated with TKI resistance can lead to a situation where neoplastic cells no longer respond to imatinib or other next-generation TKIs. The testing for these gene variants, which may include amplifications, deletions, and point mutations, is typically performed on samples obtained from blood and/or bone marrow through procedures such as venipuncture and bone marrow aspirate. The analysis is conducted using reverse transcription-polymerase chain reaction (RT-PCR) to detect the presence of these mutations.