CSF and other body fluids Flashcards
The blood brain barrier is made up of
choroid plexus and capillaries
*protects brain from microorganisms
Secretion and filtrate of the choroid plexus
Cerebrospinal fluid
*clear, colorless, sterile
Low levels of these are found in CSF
complement, antibody and phagocytes
Na, Mg, Cl are more concentrated
Examination of a sample of the fluid surrounding the brain and spinal cord
CSF analysis
*also identification of infectious agents during infection
What is the purpose of CSF analysis?
(to diagnose medical disorders that affect the CNS)
• Viral and bacterial infections
• Tumors or cancers of the CNS
•Bleeding around the brain and spinal cord
• Multiple sclerosis
• Guillain-Barré syndrome (caused by C. jejuni)
T or F: CSF collection* must be done prior to antimicrobial therapy
*follow institutional SOP
true
*Bacterial findings change even after just the first dosage administration of the antibiotic
What is used for preparing puncture site for CSF specimen collection?
- Disinfection of skin
* Use isopropyl alcohol then 2% tincture of iodine (for culture)
CSF collection techniques
- Subdural tap (extraction at fontanelle of infants)
- Ventricular aspirate (extraction directly from ventricles of the brain through catheters)
- lumbar puncture or spinal tap
During lumbar puncture, the physician inserts a thin, hollow needle in the space between two vertebra of the lower back and slowly advances it towrards what?
subarachnoid space in lumbar spine
*CSF pressure is then measured and fluid is withdrawn
Risks of lumbar puncture or spinal tap
paralysis
death
iatrogenic infection
Specimen container (three or more sterile, leak-proof tubes) numbers and analysis
1 - Chemistry
2 - Microbiology
3 - Hematology (Microscopy)
4 - Additional (i.e.: immunology, serology)
T or F: The tube that is the most turbid is the one with highest bacterial load
true
Where should aspirated material be placed in if specimen will come from brain abscess?
anaerobic container
Recommended volume for detection of microorganism
5-10 ml (in total); 2 ml for children
Consequence of inadequate volume
• Lower sensitivity
• False negative results
Solution: prioritize which laboratory test to be performed (chemical and microbiological analyses)
T or F: delivery after csf collection can be done within an hour
false, immediately
*incubate only at room temp.
*delays:
• Room temperature: microbiology
• Refrigerated: hematology (microscopy)
• Frozen: chemistry, immunology, serology
> Viral studies (-70ºC)
Why should specimen be done immediately?
- Neutrophils lyse due to hypotonicity
- Cell count decreases when kept at room temperature (1 hr= 32%; 2 hrs = 50%)
- Fastidious organisms may not survive a long delay and variation in temperature (S. pneumoniae: easily autolyzes; N. meningitidis: susceptible to cold temperature)
(see preliminary processing)
(see preliminary processing)
T or F: abnormal CSF is crystal clear
false, supernatant : (1) turbidity; (2) xanthochromia sediment: (3) blood clots
Turbidity of CSF indicates
presence of WBC, bacteria, increased protein or lipid
• ≥ 200 WBCs per mm3
• 400 RBCs per mm3
Discoloration or xanthochromia is due to
- Lysis of RBCs resulting in hemoglobin breakdown to oxyhemoglobin, methemoglobin, and bilirubin
- CSF protein ≥ 150 mg/dL
- Traumatic tap (bloody tap)
- Newborns
Why do newborns experience xanthochromia?
frequent elevation of bilirubin and protein levels (physiologic jaundice)
Interpretation of yellow CSF
- Blood breakdown products
- Hyperbilirubinemia
- Increased CSF protein
- Increased RBC
Orange CSF is most likely due to
• Blood breakdown products
• High carotenoid ingestion (especially
in children)
Pink CSF?
Blood breakdown products
Brown CSF?
meningeal melanomatosis
Green CSF is due to:
- Hyperbilirubinemia
* Purulent CSF (brain abscess)
Clots in CSF wherein there is increased filtration of protein and coagulation factors
meningitis
*traumatic tap = plasma fibrinogen
Methods of determining CSF protein
*ref ranges: 15-45 mg/dl
- Turbidimetric method (precipitation of protein: sulfosal acid + TCA, Nonne-Apelt reaction, Pandy’s test, Ross-Jones Test)
- Dye binding techniques
Method of choice for protein precipitation
TCA
ppt albumin and globulin
T or F: a larger sample size is needed in dye binding technique
false, smaller
*less interference from external sources
Dye used in dye binding techniques which bind to avariety of proteins and changes color from red to blue
Coomasie Brilliant Blue G250
- Intensity of blue color is related to the concentration of
protein
When is CSF protein elevated?
- Infections
- Intracranial hemorrhages
- Multiple sclerosis
- Guillain-Barré syndrome
- Malignancies
- Some endocrine abnormalities
- Certain medication use
- Variety of inflammatory conditions
T or F: presence of rbcs in traumatic tap falsely elevates protein in CSF
true
• Correction:
> Subtract 1 mg/dL (0.01 g/L) of protein for every 1,000 RBCs per mm3
> Accurate if the same tube is used for protein analysis and cell counts
Conditions which cause low protein in CSF
- Repeated lumbar punctures
- Chronic leak
- Acute water intoxication
- Idiopathic intracranial hypertension
- CSF protein levels do not fall in hypoproteinemia
When is CSF glucose measured?
during the preceding 2-4 hours
*immediately done because of glycolysis
What is the normal adult value of CSF glucose?
2/3 of serum glucose
T or F: Infections usually have high CSF glucose
False, low
T or F: normal glucose levels do not rule out infection
true
- Usually normal levels in viral infections
- Up to 50% of patients with bacterial meningitis will have normal CSF glucose levels
T or F: Viral infections causes elevated CSF glucose
false, There is no pathologic process that causes CSF glucose levels to be elevated
*Although elevated siya in elevated blood glucose
When is CSF blood glucose low?
- Meningitis
- Subarachnoid hemorrhage
- Inflammatory conditions
- Hypoglycemia
This is more accurate than glucose in diagnosing and managing of meningitis
CSF lactate
25 mg/dL in bacterial, fungal and TB meningitis
Where is CSF lactate seen?
oxygen depravation; falsely elevated in xanthochromic or hemolyzed fluid (lactate that are concentrated in RBCs become released)
Normal cell count in adults and newborns in CSF
Adult: 0-5 WBCs per mm3
Newborn: 0-20
Predominant WBC in adults in CSF
lymphocytes
Predominant WBC in newborns in CSF
neutrophils
Elevated WBC in CSF is caused by
- Infections and inflammatory disease
- Seizures
- Intracerebral hemorrhage
- Malignancy
- Traumatic tap
Normal cell differential count in adult CSF
70% lymphocytes
30% monocytes
T or F: Several PMNs in a neonatal patient’s CSF is normal
true
Where does abnormal cell diff count depend on
type of meningitis
see typical CSF findings in various types of meningitis
Staining methods for microbiologic analysis of CSF
• Gram staining • Acid Fast staining • Other stains: - India ink - Wright or Giemsa
percent positive found in untreated cases and partially treated cases of bacterial meningitis
untreated = 60-80% p.t. = 40-60%
Factors affecting sensitivity of gram staining
- Laboratory technique used to concentrate (i.e.: cytocentrifugation = ^ detection; ^CFU = ^+; 200-1000 rpm for 5-10 minutes)
- Experience of laboratory personnel (up to 10% of initial Gram stains are misread)
When is acid fast staining used?
if TB is clinically suspected
*increased sensitivity when: 4 smears done; CSF sediment is examined
When is india ink used?
for encapsulated organisms (i.e.: Cryptococcus)
When is Wright or Giemsa stain used?
for blood protozoa (i.e.: Toxoplasma sp.)
This increases yield as volume of CSF increases
culture
- solid media in bacterial culture: BAP, Chocolate agar (for H. influenzae and Neisseria sp.)
- Broth media: Thioglycolate, TSB
- for mycobacteria: Lowenstein-Jensen
What can decrease sensitivity of bacterial culture*?
*gold standard
antibiotic treatment prior to lumbar puncture
Principle of rapid immunologic screen for antigens
Clinical diagnosis requires detection of microorganisms as readily as possible; uses panel tax agglutination
T or F: rapid immunologic screen for antigens can replace culture
false
rapid immunologic screen for antigens
RISA
- Direct Antigen Detection Test
* PCR
RISA with rapid detection even at low levels of antigen (cases with prior antibiotic therapy)
Direct Antigen Detection Test (DADT)
- supplement to gram stain and culture
- based on latex agglutination
Most commonly isolated pathogens in DADT
H. influenza type B
- S. pneumoniae
- N. meningitidis
- Group B strep (S. agalactiae)
RISA with high sensitivity and specificity; fast; requires small volume of CSF; expensive and useful in diagnosis of VIRAL INFXNS
PCR
Other serologic tests for microbiological analysis
• Direct neurosyphilis
Venereal Disease Research Laboratory (VDRL) test, Fluorescent Treponemal Antibody Absorption (FTA-ABS) test
(see Common organisms causing acute meningitis per patient group)
(see Common organisms causing acute meningitis per patient group)
Pathologic filtrates of the circulatory system that occur due to
varying causes
Transudates and exudates
*during non-pathologic conditions: known as lymph (normal circulatory filtrate)
Accumulation of transudates/exudates in serous cavities in the body that can occur due to pathologies
Effusion
T or F: Diagnosis of pathology can be done by identifying whether the fluid is transudative or exudative
true
fluids of inflammatory origin which occurs due to increased capillary permeability or decreased lymphatic resorption
Exudates
Exudates are secondary to
- Infection (usually bacterial)
* Carcinoma/Cancer
This requires the use of chest tubes because the fluid (which contains infectious material) must be continuously drained
Exudates
Fluids of non-inflammatory origin which are ultrafiltrates of plasma through capillary endothelium
Transudates
*secondary to: • Hypoproteinuria • Venous obstruction • Cardiac failure • Disturbance in circulation with passive congestion
Characteristics of transudates
Colorless, odorless, negative coagulation, alkaline, sg < 1.018, protein content < 2.5 gm%, N or increased glucose, few cells (lympho), absent mucin
Characteristics of exudates
Darker, turbid, variable, positive coagulation, acidic, sg > 1.018, protein content >2.5 gm%, low glucose, increased cells (PMNs), present mucin
Lymph that is found in the serous cavity surrounding the lungs
Pleural fluid
Function of pleural fluid
• Function: provides a frictionless surface between two pleurae in response to changes in lung volume with respiration; for the proper expansion of the lungs
Characteristics of pleural fluid
- Volume = 1 to 10 mL
- pH 7.60 to 7.64
- Protein content <2% (1 to 2 g/dL)
- WBCs ≤ 1000/mm3
- LDH <50% of plasma
- Glucose content is similar to that of plasma/blood
- Sodium, potassium, and calcium concentration similar to that of interstitial fluid
This is the abnormal accumulation of fluid in the pleural space which results from the disruption of the fluid production and reabsorption equilibrium that exists across pleural membranes
Pleural effusion
*Indicator of a pathologic process that may be of primary pulmonary origin or of an origin related to another organ system or to systemic disease
Light’s criteria (if at least one is met; fluid is an exudate; none= transudate) IMPORTANT!!
- Pleural fluid protein to serum protein ratio > 0.5
- Pleural fluid LDH to serum LDH ratio > 0.6
- Pleural fluid LDH > 2/3 the upper limits of normal serum LDH
*If the criteria are not satisfied despite of high suspicion, you need to examine serum-to-pleural fluid albumin
® If <1.2, classify as exudate; >1.2, transudate
(see mechanisms of pleural effusion)
(see mechanisms of pleural effusion)
Why is it important to differentiate pleural fluid as exudate or transudate?
- Each fluid type suggests different pathologies, therefore the treatment to be given also varies
- Also determines whether further testing is needed
T or F: Pleural fluid analysis is only done on transudative pleural effusion
False, exudative only
*transudatives = no further work up
Pleural fluid specimen container used for determination of protein, LDH, amylase, and glucose levels (also triglyceride cholesterol level if needed)
Plain red-top tube
Pleural fluid specimen container used for CELL COUNT AND DIFF
EDTA-treated,
lavender-top tube
Pleural fluid specimen container used for pH specimen
Heparin-treated blood gas syringe
Sterile containers in pleural fluid specimen collection is used for
Gram staining and culture (for aerobic and anaerobic organisms,
mycobacteria, fungi)
50-ml heparin-treated containers are used for
cytologic analysis
Further laboratory investigation performed on exudative
effusions:
- Total protein level, glucose level, LDH level, amylase level
- pH
- Cell count with differential
- Cytological analysis
- Staining, culturing, and sensitivity testing for aerobic/anaerobic organisms
T or F: bloody pleural effusions are mostl likely an indication of malignancy in the absence of trauma; can also indicate pulmonary embolism, infection, pancreatitis, tuberculosis, mesothelioma, or spontaneous pneumothorax
true
T or F: Turbid pleural effusion is due to presence of chyle, cholesterol or empyema
false, turbid is due to increased cellular or lipid content
Yellow/whitish, turbid = chyle
What causes brown pleural (choco, anchovy paste) effusion?
Rupture of amoebic liver abscess into the pleural space (amoebiasis with a hepatopleural fistula)
Black pleural effusion is due to
aspergillus involvement of pleura
Rheumatoid pleurisy causes this pleural effusion
Yellow-green with debris
T or F: highly viscous pleural fluid is due to anaerobic infxn
false, putrid odor = anaerobic infxn.; highly viscous= malignant mesothelioma due to increased levels of hyaluronic acid; long standing pyothorax
ammonia odor in pleural effusion is due to
urinothorax
purulent pleural effusion is due to
empyema
yellow and thick effusions with melatic stain-like sheen are rich in
choletserol (longstanding chyliform effusion, e.g., tuberculous or rehumatoid pleuritis)
A low pleural fluid glucos (<60 mg/dL) is seen in
TB, malignancy, rheumatoid pleurisy
*otthers: complicated parapneumonic effusion, empyema, hemothorax, paragonimiasis, Churg-Strauss syndrome and lupus pleuritis
(occassionally)
This chemical in pleural effusion is an indicator of the degree of pleural inflammation
LDH
higher = more inflamed pleural surface
This chemical is elevated when greater than the upper limit for serum levels or when pleural fluid to serum amylase ratio is ≥ 1
Amylase
• Used for monitoring/detecting: acute pancreatitis, pancreatic pseudocyst, esophageal rupture, malignancy, and ruptured ectopic pregnancy
What does a pleural fluid pH <7.2 suggest?
- Empyema
- Paragonimiasis
- Esophageal rupture
- Hemothorax
- Rheumatoid pleuritic
- Tuberculous/Lupus pleuritis
- Malignancy
- Urinothorax
- Complicated parapneumonic effusion
