AUBF

• Cerebrospinal Fluid (CSF) is the third major fluid of the body, first recognized by Contugno in 1764.
• CSF is produced by the choroid plexus and reabsorbed in the arachnoid villi.
• The functions of CSF are to collect wastes, circulate nutrients, cushion and lubricate nervous tissues.
• The meninges line up the brain and spinal cord and are composed of three layers: Dura Mater, Arachnoid, and Pia Mater.
• CSF is produced in the choroid plexuses, which are collections of ependymal cells.
• CSF flows through the subarachnoid space and is reabsorbed back into the blood capillaries in the Arachnoid granulations / Villae.
• 20 ml of fluid is produced per hour in the choroid plexuses.
• Total CSF Volume in adults is 90-150 ml and in neonates is 10-60 ml.
• CSF is collected through ventricular puncture, cisternal puncture, or spinal tap (lumbar puncture L3, L4, L5).
• Specimens are collected in three sterile tubes: Tube 1 for Chemistry and Serology, Tube 2 for Microbiology, Tube 3 for Hematology, and Tube 4 may be used for microbiology to exclude skin contamination.
• Normal clots are due to the absence of fibrinogen.
• The functions of synovial fluid are to reduce friction between bones during movement, provide lubrication in the joints, provide nutrients to the articular cartilage, lessen joint compression during walking and jogging, and it can be collected through arthrocentesis.
• Tuberculous meningitis increases WBC count, decreases glucose levels, and increases lymphocytes.
• Normal synovial fluid volume is less than 3.5 mL, color is colorless to pale yellow, appearance resembles egg white, clarity is clear, and viscosity must form a 4-6cm long string (String Test).
• Bacterial meningitis increases WBC count markedly, decreases glucose levels markedly, and increases neutrophils, lymphocytes, and eosinophils.
• Immunological tests for CSF include latex agglutination/ELISA for bacterial antigens and VDRL (serum and CSF) for neurosyphilis (tertiary syphilis).
• Total WBC count is the most frequently performed test in synovial fluid analysis.
• Fungal meningitis increases WBC count, decreases glucose levels, and increases lymphocytes.
• Joint disorders can be non-inflammatory (degenerative joint disorders, orteoarthritis) or inflammatory (immunologic, crystal-induced, septic, hemorrhagic).
• Parasitic meningitis increases WBC count, decreases glucose levels, and increases eosinophils.
• Viral meningitis increases WBC count normally, maintains glucose levels normally, and increases lymphocytes.
• Variations in clotting can lead to paresis (incomplete paralysis), large clots associated with purulent meningitis, web-like clots in TB meningitis, and clotting en masse which can block CSF circulation.
• Synovial fluid, also known as joint fluid, contains high levels of Hyaluronic acid and is the fluid circulating in the moveable joints (diarthroses) of the body.
• CSF tests are done on a STAT (Latin statim – immediately) basis (Short turn-around-time).
• If not analyzed immediately, cells deteriorate with time, glucose undergoes glycolysis, and bacteria proliferate and multiply.
• Dense, crystalline concretions are characteristic of brocholithiasis.
• Charcot-Leyden crystals are characteristic of asthma.
• Alveolar proteinosis is characterized by PAS positive rounded bodies that take silver stain.
• Chronic bronchitis or bronchiectasis is characterized by PAS-positive macrophages.
• Asthma or pulmonary hypersensitivity reaction is characterized by numerous eosinophils in abundant mucus, with few or no organisms.
• Gastric fluid analysis is important in pernicious anemia, peptic ulcer, Zollinger-Ellison disease.
• Sweat is collected using Pilocarpine Iontophoresis and tested for the levels of Sodium & Chloride.
• Hydrochloric acid is produced by parietal cells, pepsinogen is produced by chief cells and with the action of HCl becomes pepsin, gastrin is produced by G-cells that stimulate parietal cells to produce HCl, and Zollinger-Ellison disease is characterized by increased gastrin level and gastric acid hypersecretion.
• Cystic fibrosis is characterized by bulky offensive greasy stools, noticeably salty sweat, frequent respiratory infections and chronic cough, malnutrition, and male infertility (obstructive azoospermia).
• Lipid droplets in macrophages are characteristic of lipoid or aspiration pneumonia.
• Heart Failure cells are large mononuclear cells with brown blood pigment.
• Cortschmann’s spirals are characteristic of asthma.
• Fecal fat testing is used for diagnosis of Steatorrhea and can be done qualitatively or quantitatively.
• Epithelial cells are mostly found in saliva and contain numerous neutrophils, which are often associated with intra- and extracellular organisms.
• Myelin globules may resemble Blastomyces or fat droplets, with no clinical significance.