body fluids Flashcards
Body Fluids
Precious specimens: cannot be recollected without undue harm to the patient. If these specimens are
improperly labelled, we do not reject the specimen. Testing can occur following specific lab
procedures
•Cerebrospinal Fluid (CSF)
•Serous
- Pleural (lung)
- Pericardial (heart)
- Peritoneal (abdominal)
•Synovial (joint)
•Amniotic
Others:
•Semen
•Sweat
•Feces
Cerebrospinal Fluid (CSF)
- liquid that surrounds the brain and spinal cord.
- produced in the choroid plexuses.
- The brain and spinal cord are lined by meninges that consist of three layers:
- Dura mater ( outter)
- Arachnoid( middle)
- Pia mater ( inner)
- The CSF flows between the arachnoid and the pia mater in the subarachnoid space.
- Adults maintain a volume of 90-150 mL; Neonates 10-60 mL
Functions of CSF
- Physical support and protection
- Cushions the brain and spinal cord to protect against trauma - Provides a controlled chemical environment to supply nutrients to tissues and remove metabolic wastes
- Maintain intracranial pressure
CSF - Formation and Physiology
- Formation
- Formed predominantly at choroid plexuses( capillary network) deep within brain by cells lining ventricles
•About 500 mL/day formed
- Formation results from selective filtration of plasma & active transport secretion.
- Tight-fitting endothelial cells prevent filtration of large molecules—called the blood-brain barrier.
Blood-Brain Barrier
•Control the passage of substances across their membranes is known as the blood-brain barrier.
- Prevents large molecules, chemicals and harmful substances from reaching the brain.
- Damage to the blood-brain barrier allow leukocytes, proteins, and other chemicals to enter the CSF.
•This can be caused by diseases such as multiple sclerosis or meningitis
` CSF analysis will be abnormal in these cases
CSF Collection and Handling
•CSF is collected by lumbar puncture at the interspace of vertebrae L3 or lower.
•Three sterile tubes are collected in numbered aliquots:
1. Chemistry/Serology
•Tests are least affected by contamination from blood or bacteria
- Microbiology
•Less tissue/skin contamination - Hematology
•Used for cell counts
•Least likely to contain cells introduced from the spinal tap procedure
*dr may specify a different order
•A fourth tube may sometimes be collected for additional tests.
- Specimens will have a limited volume and should be handled carefully.
•CSF analysis is a STAT test. Analyze immediately!
- Always keep any fluid remaining and preserve according to laboratory policy:
- Hematology - Refrigerate
- Microbiology - Room temperature
- Chemistry/Serology - Frozen
What happens if only one tube is collected?
The order of the labs change. The one tube will be passed between the labs in the following order:
1. Microbiology
•Less handling/contamination is best for culturing
- Hematology
•Cell counts need to be done before sample is centrifuged by chemistry lab - Chemistry
•Tests are least affected by any previous handling/contamination
CSF Physical Appearance
•Normal CSF is clear and colorless
•Abnormal appearances:
•Cloudy, Turbid, Milky - increased protein or lipid concentration or infection (↑ WBCs)
•Bloody - RBCs from hemorrhage or traumatic tap
•Xanthochromic - pink, orange or yellow CSF
- Caused by RBC degradation products
Traumatic Tap
•A traumatic tap occurs when a blood vessel is punctured during the lumbar puncture.
- *It is important to differentiate a cerebral hemorrhage from a traumatic tap.
- CSF samples from both will appear bloody.
•To differentiate:
•Hemorrhage - will have even blood distribution in all tubes
- no clots (does not have enough fibrinogen to clot)
- xanthochromic supernatent( unless it was a recent hemorrhage; rbcs take a few hrs to degrade)
•Traumatic tap - will have decreasing amounts of blood in tubes 1 to 3.
- may have streaks of blood
- may have clots present
Hematology CSF Testing - Cell Count
- A cell count is done using an improved Neubauer counting chamber
- It is normal to find 0 - 5 WBCs/μL
- Lymphocytes 40-80% ( mostly )
- Monocytes 15-45%
- Occasional neutrophils <6%
- may need to dilute if cells are overlapping
- count right away;RBCs disintegrate ~1hr, 40% WBCs in ~2hrs
- refrigerate no longer than 4 hrs
- A stained smear is used to differentiate between the types of WBCs.
- RBCs should not be present
Increased Number of Cells
An increased number of cells is called Pleocytosis and is an abnormal finding in a CSF.
Type of Cell Major Clinical Significance if Increased
Lymphocytes ……………………….Viral, tubercular, and fungal meningitis, Multiple Sclerosis
Neutrophils………………………. Bacterial meningitisEarly cases of viral, tubercular, and fungal meningitis
Monocytes ………………………………Viral, tubercular, and fungal meningitisMultiple Sclerosis
Macrophages………………………… RBCs in spinal fluid due to a hemorrhage
Plasma Cells……………………………. Multiple Sclerosis
Chemistry CSF Testing - Protein
Total protein is the most frequently performed test.
- The normal range is 15-45 mg/dL (150-450 mg/L)
- Albumin makes up most of CSF protein; Prealbumin is second most prevalent protein.
- Other fractions of protein seen in CSF:
- Alpha globulin - haptoglobin and ceruloplasmin
- Beta globulin - transferrin and tau transferrin
- Gamma globulin - mostly IgG, with a small about of IgA
- IgM, fibrinogen and beta lipoprotein are not found in normal CSF.
- Analysis of CSF protein can be done on automated chemistry analyzers using the principles of nephelometry or dye-binding.
Chemistry CSF Testing - Electrophoresis
CSF needs to be conc. first bc of low levels of protein
•Electrophoresis is performed on CSF to detect oligoclonal bands.
-small number of clones of IgG from the same cell type with nearly identical electrophoretic
properties.
•Associated with :
inflammatory diseases such as Multiple Sclerosis (MS) as well as encephalitis, neurosyphilis, Guillain-Barré syndrome, and neoplastic disorders.
•Serum should be tested simultaneously to determine if the bands are a result of a neurologic inflammation.
- MS - no bands in serum; two or more bands in CSF - Leukemia, lymphoma, viral infections - bands in both serum & CSF
Chemistry CSF Testing - Myelin Basic Protein (MBP)
- Myelin Basic Protein in CSF indicates recent destruction of the myelin sheath that protects the axons of neurons
- MBP is used to monitor therapy in patients with multiple sclerosis.
- Analysis is done by immunoassay techniques.
