CPT® Code 81373

The HLA Class I typing, low resolution (CPT® Code 81373) is a laboratory procedure that focuses on identifying specific genetic markers known as human leukocyte antigens (HLAs) within the Class I category. The HLA system is a critical component of the major histocompatibility complex (MHC), which plays a vital role in the immune system by facilitating self-recognition. This means that the MHC helps the body distinguish its own cells and tissues from foreign invaders, such as pathogens and nonself cells. HLAs are located on the short arm of chromosome 6 and are essential for the immune system's normal functioning. Within the HLA system, there are two main classes: Class I and Class II, with Class I being particularly significant for immune responses. The most important loci within Class I are HLA-A, HLA-B, and HLA-C. Each of these loci can have multiple variants known as alleles, which are designated by the locus name followed by an asterisk (*) and a series of digits that provide specific information about the allele. For example, HLA-B*08:01 indicates a specific allele within the HLA-B locus. The low resolution typing of HLA Class I is particularly useful in various medical contexts, including organ transplantation, where matching donor and recipient HLAs can significantly impact the success of the transplant. Additionally, HLAs are involved in the body's defense against diseases, including certain cancers and autoimmune disorders. The procedure typically involves molecular techniques for DNA extraction, which require cell lysis and protein digestion. Polymerase chain reaction (PCR) is commonly employed in this process, specifically using a method called PCR sequence specific priming (SSP) to amplify groups of alleles. CPT® Code 81373 is specifically used when low resolution testing is performed for a single HLA Class I locus, such as HLA-A, HLA-B, or HLA-C. For comprehensive low resolution typing that includes all three loci, CPT® Code 81372 should be used. In cases where low resolution testing is aimed at identifying a specific Class I antigen equivalent, such as B*27, CPT® Code 81374 is applicable.