protein in cerebrospinal fluid (CSF)

Reference interval

• Male & Female: 12 - 60 mg/dL
• mean CSF protein: 52 mg/dL
• range: 14-148 mg/dL; 95% reference interval: 24-93 mg/dL
• mean levels vary by age: 44 mg/dL (age 30-50); 58 mg/dL (age > 80)
• broad variation in every age group
• older age, male sex, diabetes mellitus, spinal stenosis predict higher CSF protein

Principle

The Kodak Ektachem Clinical Chemistry Slide (PROT) quantitatively measures proteins in cerebrospinal fluid. PROT is a End-Point Colorimetric Test.

The Kodak Ektachem Clinical Chemistry Slide (PROT) is a dry, multilayered, self-contained analytical element coated on a transparent polyester support.

A 10 uL drop of sample is deposited on the slide & is evenly distributed by the spreading layer. Protein in the sample forms a complex with cupric ion from the results in the dissociation of the cupric ion from the copper-azo dye complex. The decrease of the copper-azo dye complex is measured by reflectance spectrophotometry & is proportional to the concentration of protins in the sample. The assay wavelength is 670 nm. Assay time is approximately 5 minutes, & assay temperature is 37 C.

Clinical significance

• cerebrospinal fluid (CSF) proteins are those that remain in CSF following ultrafiltration of plasma through the choroid capillary wall
• some proteins that are unique to CSF are synthesized in the nervous system
• diseases that interrupt the integrity of the capillary endothelial barrier lead to an increase in total CSF protein

Increases

• in all types of meningitis
• cerebral infarction
• brain abscess
• meningovascular syphilis (tertiary syphilis)
• subarachnoid hemorrhage
• some brain tumors
• myelitis
• neurodegenerative diseases

Decreases

• water intoxication
• CSF leak (CSF rhinorrhea or otorrhea)
• hyperthyroidism

Specimen

The recommended specimen is 10 uL of cerebrospinal fluid (CSF). Special Precautions: Specimens containing EDTA should not be used. Hemolyzed specimens should not be used since hemoglobin is a protein & will cause an increase in the measurement of CSF protein. Specimens should be collected prior to the intrathecal administration of contrast media. Significant positive bias can occur when CSF contains contrast media such as Iopamidol, Isohexol, & Metrazimide. Handle specimens in closed containers to avoid contamination & evaporation. Refrigerate specimens at 2-8 C if analysis is not performed within four hours; or freeze specimens at -18 degrees C if analysis is not performed within 48 hours. Centrifuge every CSF specimen to remove any cellular protein if present.

Minimum sample size is 0.5 milliliter; with an optimum size of 1.0 milliliter or larger.

Dilution is not required for routine testing. Samples with CSF protein concentrations that exceed the analyzer's dynamic range can be diluted with isotonic saline & reanalyzed. Multiply the results by the dilution factor to obtain final results. Sterile water is not recommended for use as a diluent. The dynamic range for (PROT) on the Kodak Ektachem 700 Analyzer is 10 - 300 mg/dL.

Interferences

• Preliminary data indicated that hemolysis, icterus & lipemia do not interfere with this method.
• Dextran, Salicylic acid & Ascorbic acid will cause a positive bias at normal protein levels.
• Intrathecal drug levels for vancomycin & ampicillin at high concentrations can diffuse across inflamed meninges. Vancomycin at 10 mg/dL (Intrathecal) may show an average positive bias of 13 mg/dL at normal protein levels, & ampicillin at 10 mg/dL (Intrathecal) may show an average positive bias at 21 mg/dL at normal protein levels.

More general terms

• protein in body fluid

More specific terms

• globulin in CSF

Additional terms

• cerebrospinal fluid

Component of

• microtubule-associated protein tau/total protein in CSF
• alpha-2 globulin/protein.total in CSF
• alpha-1 globulin/protein.total in CSF
• beta-2 globulin/total protein in CSF
• beta-1 globulin/total protein in CSF
• albumin/protein total in CSF
• cerebrospinal fluid analysis