Общий белок (TP)

CSF Total Protein (cerebrospinal fluid total protein; total protein, CSF) quantifies the overall protein concentration in cerebrospinal fluid and serves as a broad indicator of blood–brain barrier integrity, intrathecal protein synthesis, and CSF circulation or resorption. The test supports evaluation of suspected infectious, inflammatory, neoplastic, and autoimmune disorders of the central nervous system and can be used to track response to therapy or disease activity over time.

Cerebrospinal fluid analysis provides direct insight into central nervous system physiology and disease. Total protein in adult CSF typically ranges from 150–500 mg/L (0.15–0.5 g/L). Approximately 80% of CSF protein derives from plasma via filtration at the choroid plexus, with a smaller fraction produced intrathecally by choroid plexus epithelium, glia, neurons, and immune cells. Albumin is the predominant CSF protein (about 35–80% of total), and immunoglobulins in normal CSF are mainly IgG; the majority of IgG enters from blood rather than being synthesized within the CNS. Because of the blood–brain barrier, smaller proteins traverse more readily than larger ones: albumin equilibrates over roughly one day, whereas IgM may require several days. Overall, CSF protein content represents only about 0.1–0.2% of serum protein. CNS‑specific proteins such as myelin basic protein, glial fibrillary acidic protein, and tau are detectable but together usually account for only 1–2% of total CSF protein. Elevated CSF total protein arises through three principal mechanisms: increased blood–brain barrier permeability (common in infectious–inflammatory conditions), augmented intrathecal synthesis (for example, in multiple sclerosis, sarcoidosis, or neurosyphilis), and impaired CSF protein resorption through arachnoid granulations. Marked increases occur in bacterial meningitis (0.4–4.4 g/L), cryptococcal meningitis (0.3–3.1 g/L), and tuberculous meningitis (0.2–1.5 g/L), and may be seen in neuroborreliosis. A concentration above 1.5 g/L has about 99% specificity for bacterial meningitis. In viral neuroinfections such as encephalitis and meningoencephalitis, elevations are typically smaller (usually <0.95 g/L), and CSF total protein remains normal in approximately half of patients with herpes simplex encephalitis. Increased values also occur with subarachnoid hemorrhage, CNS vasculitides, and malignant CNS involvement. Albuminocytologic dissociation—elevated protein with a normal CSF cell count—is characteristic of acute and chronic inflammatory demyelinating polyneuropathies; however, levels can be normal during the first week of illness. Protein is elevated in about 80% of patients with leptomeningeal metastases (mean around 1 g/L), and modest increases can accompany peripheral neuropathies such as diabetic neuropathy. Reduced CSF total protein may follow repeated lumbar punctures or chronic CSF leak and can be observed in some children aged 6 months to 2 years, in water intoxication, and in some cases of idiopathic intracranial hypertension. Age and preanalytical factors influence results: infants generally exhibit higher CSF protein than adults, with adult levels reached by about 6–12 months, and a traumatic tap with numerous erythrocytes can artifactually increase measured protein. Reference intervals vary by laboratory and method; for serial assessment, testing should be performed in the same laboratory. Because CSF protein quantity and composition are closely linked to serum protein, concurrent measurement of blood protein is recommended.