CPT® Code 83518

Immunoassay for analyte other than infectious agent antibody or infectious agent antigen; qualitative or semiquantitative, single step method (eg, reagent strip)

An immunoassay is a laboratory procedure designed to detect the presence of a specific chemical substance, known as an analyte, in a sample. This particular CPT® Code 83518 refers to immunoassays that are utilized for substances other than antibodies or antigens related to infectious agents. The tests can be qualitative, which means they determine whether the analyte is present or absent, or semiquantitative, which provides an approximate measurement of the analyte's concentration. The single-step method, such as a reagent strip, is specifically indicated by this code. This type of testing is commonly employed in the diagnosis and management of various non-infectious diseases and disorders, including but not limited to celiac disease, motor and sensory neuropathy, Crohn's disease, liver disease, and thyroid disease. The immunoassays can target specific immunoglobulin classes or subclasses, such as Asialo IgG, IgM, ganglioside IgG, IgM, and gliadin IgA, IgG. It is important to note that each class or subclass tested using this method is reported separately. For instance, if both gliadin IgA and IgG are tested, the code 83518 would be reported twice. This code is distinct from CPT® Code 83516, which is used for qualitative or semiquantitative immunoassays that employ a multistep method.