CPT® Code 86651

The CPT® Code 86651 refers to a laboratory test specifically designed to measure antibodies related to California (La Crosse) encephalitis in either blood or cerebrospinal fluid (CSF). California encephalitis is caused by a mosquito-borne virus belonging to the bunyaviridae family, which typically results in a mild illness, particularly in children during the late summer months. The clinical presentation of this infection often includes symptoms such as a stiff neck and lethargy, which generally appear approximately one week following exposure to the virus and can persist for up to ten days. In some cases, patients may experience seizures either during the acute phase of the infection or as a long-term consequence of the disease. The laboratory test measures specific antibodies: a positive titer for immunoglobulin G (IgG) antibodies indicates either a current or past infection, while a positive titer for immunoglobulin M (IgM) antibodies, when coupled with clinical suspicion of California (La Crosse) viral infection, suggests a current or recent infection. To perform this test, a blood sample is collected through a separately reportable venipuncture, and if CSF is required, it is obtained via a separately reportable lumbar puncture. The testing of both serum and CSF samples is conducted using a semi-quantitative indirect fluorescent antibody technique, which allows for the detection and measurement of these specific antibodies.