CPT® Code 81233

The CPT® Code 81233 pertains to the analysis of the BTK (Bruton's tyrosine kinase) gene, specifically focusing on common variant mutations associated with chronic lymphocytic leukemia (CLL). This molecular genetic testing is crucial for identifying specific mutations, namely C481S, C481R, and C481F, which occur at the cysteine 481 codon within the kinase domain of the BTK gene. The BTK gene is located on the long (q) arm of the X chromosome at position 22.1 (Xq22.1) and plays a vital role in the development and function of B-cells, a type of white blood cell responsible for producing antibodies that help the body fight infections. The identified mutations are characterized by single amino acid substitutions: C481S replaces cysteine with serine, C481R replaces cysteine with arginine, and C481F replaces cysteine with phenylalanine. These mutations are significant as they are linked to acquired resistance to targeted therapies such as ibrutinib and acalabrutinib, which are commonly used in the treatment of CLL and mantle cell lymphoma. The testing can be conducted prior to the initiation of treatment or during the course of therapy to inform clinical decisions and optimize patient management.