CPT® Code 84394

The CPT® Code 84394 refers to the measurement of total tau protein (tTau) in the blood, which is a significant biomarker associated with Alzheimer's disease. Neurofibrillary tangles, which are formed by the abnormal deposition of tau protein in the brain, represent one of the two primary neuropathological features of Alzheimer's disease. These tangles develop within neurons due to the accumulation of hyperphosphorylated tau, a process that typically begins 10 to 15 years prior to the onset of clinical symptoms. The presence of tau tangles is closely linked to the earlier formation of beta-amyloid plaques, the other hallmark of Alzheimer's pathology. Recent advancements in blood testing have introduced p-Tau 217 as a novel marker, which has shown promise in indicating the presence of neuropathological changes associated with Alzheimer's disease. Elevated levels of p-Tau 217 in blood samples are particularly noteworthy, as they may provide a more accurate differentiation between Alzheimer's disease and other frontotemporal lobe degenerative diseases. This is due to p-Tau 217 being a stronger indicator of amyloid activity and tau binding, as evidenced by findings from PET scans of the temporal cortex. The testing for both p-Tau proteins is conducted using electrochemiluminescence-based assays, which are sensitive and specific for these biomarkers. For accurate coding, it is essential to report CPT® Code 84393 for each individual protein tested and CPT® Code 84394 for the total tau test.