Body Fluids
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CSF Flows where? Functions?
• Flows in subarachnoid space • Functions to give physical support/protection, controlled chem environment to supply nutrients/remove wastes, and transport
Lumbar puncture area and tube order
• L3/L4 1. Chemistry/Serology 2. Microbiology 3. Hematology 4. Extra/cytology
Why investigate CSF?
• Infection • Demyelinating disease • Malignancy • Hemorrhage into CNS
What color is xanthrochromic CSF and why is it that color?
Yellow due to bilirubin from RBC breakdown in old hemorrhage
T/F: CSF from fresh hemorrhage tends to clot
False CSF from traumatic tap (decreasing amounts of redness in each successive tube) tends to clot
4 main markers in CSF
• Glucose • Protein (total/specific) • Lactate • Glutamine
How to prep CSF specimen for analysis
Always centrifuge even if clear/colorless!
Glucose in CSF CSF transport When to collect Conc in CSF
• Enters CSF through facilitative protein transport • Collect blood glucose 2-4 hrs prior • CSF glucose conc 60-70% of plasma glucose (but no longer applies once >600 mg/dL)
Hypoglycorrhachia
Decreased CSF glucose levels
Causes of hypoglycorrhachia + examples
• Disorder in carrier-mediated transport of glucose into CSF • Active metabolism of glucose by cells/organisms • Increased metabolism by CNS • Examples: meningitis, meningeal neoplasia, brain tumor
Consumption of glucose usually has increased _____ level due to ______ glycolysis by organisms or tissue
Lactate anaerobic
What do CSF protein levels reflect?
Selective ultrafiltration of CSF blood-brain barrier
Total protein conc in CSF
0.5%-1.0% of plasma Not proportional due to specificity of ultrafiltration process
Which analysis should accompany CSF protein analysis?
Serum
Causes of decreased protein CSF
• Decreased dialysis of proteins from plasma • Increased protein loss (removal of excessive volumes of CSF) • Leakage from a tear in the dura, CSF otorrhea (ear), or CSF rhinorrhea (nose)
How to detect CSF leakage
Analysis of beta-transferrin bc it’s unique to CSF
Causes of increased protein in CSF
• Lysis of contaminant blood from traumatic tap • Increased permeability of epithelial membrane • Increased production by CNS tissue obstruction
How do bacterial/fungal infections affect the BBB?
Increase permeability
T/F: Protein in CSF is NOT diagnostic of infectious meningitis - helpful though
True
Normal CSF and serum prealbumin conc. Why is it measured in both?
• CSF > serum conc • Used to normalize IgG values to determine source
Describe proteins of highest interest in CSF
• Albumin: must cross BBB • IgG: Can be produced by local synthesis from plasma cells within the CSF
Index value of protein which indicates intact BBB
protein index < 9
IgG index How to calculate What does it help diagnose Normal value
• Use CSF serum index • Helps diagnose demyelinating diseases (MS, SSPE) • Normal IgG < 0.73
How does serum albumin affect CSF levels?
Increases CSF levels due to membrane permeability