cerebrospinal fluid analysis

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cerebrospinal fluid analysis

Lab medicine The in vitro evaluation of the CSF. See Lumbar puncture.

Cerebrospinal fluid analysis

A analysis that is important in diagnosing diseases of the central nervous system. The fluid within the spine will indicate the presence of viruses, bacteria, and blood. Infections such as encephalitis will be indicated by an increase of cell count and total protein in the fluid.
Mentioned in: Encephalitis

Cerebrospinal Fluid Analysis

Synonym/acronym: CSF analysis.

Common use

To assist in the differential diagnosis of infection or hemorrhage of the brain. Also used in the evaluation of other conditions with significant neuromuscular effects, such as multiple sclerosis.

Specimen

CSF (1 to 3 mL) collected in three or four separate plastic conical tubes. Tube 1 is used for chemistry and serology testing, tube 2 is used for microbiology, tube 3 is used for cell count, and tube 4 is used for miscellaneous testing.

Normal findings

(Method: Macroscopic evaluation of appearance; spectrophotometry for glucose, lactic acid, and protein; immunoassay for myelin basic protein; nephelometry for immunoglobulin G [IgG]; electrophoresis for oligoclonal banding; Gram stain, India ink preparation, and culture or PCR for microbiology; microscopic examination of fluid for cell count; flocculation for Venereal Disease Research Laboratory [VDRL])
Lumbar PunctureConventional UnitsSI Units
Color and appearanceCrystal clear
(Conventional Units × 10)
Protein
 0–1 moLess than 150 mg/dLLess than 1,500 mg/L
 1–6 mo30–100 mg/dL300–1,000 mg/L
 7 mo–adult15–45 mg/dL150–450 mg/L
 Older adult15–60 mg/dL150–600 mg/L
(Conventional Units × 0.0555)
Glucose
 Infant or child60–80 mg/dL3.3–4.4 mmol/L
 Adult/older adult 40–70 mg/dL2.2–3.9 mmol/L
(Conventional Units × 0.111)
Lactic acid
 Neonate10–60 mg/dL 1.1–6.7 mmol/L
 3–10 days10–40 mg/dL1.1–4.4 mmol/L
 AdultLess than 25.2 mg/dLLess than 2.8 mmol/L
(Conventional Units × 1)
Myelin basic protein
Less than 4 ng/mLLess than 4 mcg/L
Oligoclonal bandsAbsent
(Conventional Units × 10)
IgGLess than 3.4 mg/dLLess than 34 mg/L
Gram stainNegative
India inkNegative
CultureNo growth
RBC count00
(Conventional Units × 1)
WBC count
Neonate–1 mo0–30 /microL0–30 × 106/L
 1 mo–1 yr0–10 /microL 0–10 × 106/L
 1–5 yr0–8 /microL 0–8 × 106/L
 5 yr–adult0–5 /microL 0–5 × 106/L
VDRLNonreactive
CytologyNo abnormal cells seen
CSF glucose should be 60%–70% of plasma glucose level.RBC = red blood cell; VDRL = Venereal Disease Research Laboratory; WBC = white blood cell.Color should be assessed after sample is centrifuged.
WBC DifferentialAdultChildren
Lymphocytes40%–80%5%–13%
Monocytes15%–45%50%–90%
Neutrophils0%–6%0%–8%

Description

Cerebrospinal fluid (CSF) circulates in the subarachnoid space and has a twofold function: to protect the brain and spinal cord from injury and to transport products of cellular metabolism and neurosecretion. The total volume of CSF is 90 to 150 mL in adults and 60 mL in infants. CSF analysis helps determine the presence and cause of bleeding and assists in diagnosing cancer, infections, and degenerative and autoimmune diseases of the brain and spinal cord. Specimens for analysis are most frequently obtained by lumbar puncture and sometimes by ventricular or cisternal puncture. Lumbar puncture can also have therapeutic uses, including injection of drugs and anesthesia. The subspeciality of microbiology has been revolutionized by molecular diagnostics. Molecular diagnostics involves the identification of specific sequences of DNA. The application of molecular diagnostics techniques, such as PCR, has led to the development of automated instruments that can identify a single infectious agent or multiple pathogens from a cerebrospinal fluid sample in less than 2 hr. The instruments can detect the presence of bacteria, viruses, and yeast commonly associated with meningitis and encephalitis.

This procedure is contraindicated for

  • high alertPatients with infection present at the needle insertion site.
  • high alertPatients with degenerative joint disease or coagulation defects.
  • high alertPatients who are uncooperative during the procedure.
  • high alertPatients with increased intracranial pressure; extreme caution should be used because overly rapid removal of CSF can result in herniation.

Indications

  • Assist in the diagnosis and differentiation of subarachnoid or intracranial hemorrhage
  • Assist in the diagnosis and differentiation of viral or bacterial meningitis or encephalitis
  • Assist in the diagnosis of diseases such as multiple sclerosis, autoimmune disorders, or degenerative brain disease
  • Assist in the diagnosis of neurosyphilis and chronic central nervous system (CNS) infections
  • Detect obstruction of CSF circulation due to hemorrhage, tumor, or edema
  • Establish the presence of any condition decreasing the flow of oxygen to the brain
  • Monitor for metastases of cancer into the CNS
  • Monitor severe brain injuries

Potential diagnosis

Increased in

  • Color and appearance (xanthochromia is any pink, yellow, or orange color; bloody—hemorrhage; xanthochromic—old hemorrhage, red blood cell [RBC] breakdown, methemoglobin, bilirubin [greater than 6 mg/dL], increased protein [greater than 150 mg/dL], melanin [meningeal melanosarcoma], carotene [systemic carotenemia]; hazy—meningitis; pink to dark yellow—aspiration of epidural fat; turbid—cells, microorganisms, protein, fat, or contrast medium)
  • Protein (related to alterations in blood-brain barrier that allow permeability to proteins): meningitis, encephalitis
  • Lactic acid (related to cerebral hypoxia and correlating anaerobic metabolism): bacterial, tubercular, fungal meningitis
  • Myelin basic protein (related to accumulation as a result of nerve sheath demyelination): trauma, stroke, tumor, multiple sclerosis, subacute sclerosing panencephalitis
  • IgG and oligoclonal banding (related to autoimmune or inflammatory response): multiple sclerosis, CNS syphilis, and subacute sclerosing panencephalitis
  • Gram stain: Meningitis due to Escherichia coli, Streptococcus agalactiae, Streptococcus pneumoniae, Haemophilus influenzae, Mycobacterium avium-intracellulare, Mycobacterium leprae, Mycobacterium tuberculosis, Neisseria meningitidis, Cryptococcus neoformans
  • India ink preparation: Meningitis due to C. neoformans
  • Culture: Encephalitis or meningitis due to herpes simplex virus, S. pneumoniae, H. influenzae, N. meningitidis, C. neoformans
  • RBC count: Hemorrhage
  • White blood cell (WBC) count:
    • General increase—injection of contrast media or anticancer drugs in subarachnoid space; CSF infarct; metastatic tumor in contact with CSF; reaction to repeated lumbar puncture
    • Elevated WBC count with a predominance of neutrophils indicative of bacterial meningitis
    • Elevated WBC count with a predominance of lymphocytes indicative of viral, tubercular, parasitic, or fungal meningitis; multiple sclerosis
    • Elevated WBC count with a predominance of monocytes indicative of chronic bacterial meningitis, amebic meningitis, multiple sclerosis, toxoplasmosis
    • Increased plasma cells indicative of acute viral infections, multiple sclerosis, sarcoidosis, syphilitic meningoencephalitis, subacute sclerosing panencephalitis, tubercular meningitis, parasitic infections, Guillain-Barré syndrome
    • Presence of eosinophils indicative of parasitic and fungal infections, acute polyneuritis, idiopathic hypereosinophilic syndrome, reaction to drugs or a shunt in CSF
  • VDRL: Syphilis

Positive findings in:

  • Cytology: Malignant cells

Decreased in

    Glucose: Bacterial and tubercular meningitis

Critical findings

  • Positive Gram stain, India ink preparation, or culture
  • Presence of malignant cells or blasts
  • Elevated WBC count
  • Adults: Glucose less than 37 mg/dL (SI: Less than 2.1 mmol/L); greater than 440 mg/dL (SI: Greater than 24.4 mmol/L)
  • Children: Glucose less than 31 mg/dL (SI: Less than 1.7 mmol/L); greater than 440 mg/dL (SI: Greater than 24.4 mmol/L)
  • Note and immediately report to the health-care provider (HCP) any positive or critically increased results and related symptoms.

  • It is essential that a critical finding be communicated immediately to the requesting HCP. A listing of these findings varies among facilities.

  • Timely notification of a critical finding for lab or diagnostic studies is a role expectation of the professional nurse. Notification processes will vary among facilities. Upon receipt of the critical value the information should be read back to the caller to verify accuracy. Most policies require immediate notification of the primary HCP, Hospitalist, or on-call HCP. Reported information includes the patient’s name, unique identifiers, critical value, name of the person giving the report, and name of the person receiving the report. Documentation of notification should be made in the medical record with the name of the HCP notified, time and date of notification, and any orders received. Any delay in a timely report of a critical finding may require completion of a notification form with review by Risk Management.

Interfering factors

  • Other considerations

    • Drugs that may decrease CSF protein levels include cefotaxime and dexamethasone.
    • Interferon-β may increase myelin basic protein levels.
    • Drugs that may increase CSF glucose levels include cefotaxime and dexamethasone.
    • RBC count may be falsely elevated with a traumatic spinal tap.
    • Delays in analysis may present a false positive appearance of xanthochromia due to RBC lysis that begins within 4 hr of a bloody tap.

Nursing Implications and Procedure

Pretest

  • Positively identify the patient using at least two unique identifiers before providing care, treatment, or services.
  • Patient Teaching: Inform the patient this procedure can assist in evaluating health by providing a sample of fluid from around the spinal cord to be tested for disease and infection.
  • Obtain a history of the patient’s complaints, including a list of known allergens, especially allergies or sensitivities to latex or anesthetics.
  • Obtain a history of the patient’s immune and musculoskeletal systems and results of previously performed laboratory tests and diagnostic and surgical procedures.
  • Obtain a list of the patient’s current medications, including herbs, nutritional supplements, and nutraceuticals (see Effects of Natural Products on Laboratory Values online at DavisPlus).
  • Review the procedure with the patient. Inform the patient that the position required may be awkward but that someone will assist during the procedure. Stress the importance of remaining still and breathing normally throughout the procedure. Inform the patient that specimen collection takes approximately 20 min. Address concerns about pain and explain that a stinging sensation may be felt when the local anesthetic is injected. Instruct the patient to report any pain or other sensations that may require repositioning the spinal needle. Explain that there may be some discomfort during the procedure. Inform the patient the procedure will be performed by an HCP.
  • Sensitivity to social and cultural issues, as well as concern for modesty, is important in providing psychological support before, during, and after the procedure.
  • Note that there are no food, fluid, or medication restrictions unless by medical direction.
  • Make sure a written and informed consent has been signed prior to the procedure and before administering any medications.

Intratest

  • Potential complications:
  • Headache is a common minor complication experienced after lumbar puncture and is caused by leakage of the spinal fluid from around the puncture site. On a rare occasion the headache may require treatment with an epidural blood patch in which an anesthesiologist or pain management specialist injects a small amount of the patient’s blood in the epidural space of the puncture site. The blood patch forms a clot and seals the puncture site to prevent further leakage of CSF and provides relief within 30 min. Other complications include lower back pain after the procedure, bleeding near the puncture site, or brainstem herniation, due to increased intracranial pressure.

  • Avoid the use of equipment containing latex if the patient has a history of allergic reaction to latex.
  • Ensure that anticoagulant therapy has been withheld for the appropriate number of days prior to the procedure. Number of days to withhold medication is dependent on the type of anticoagulant. Notify HCP if patient anticoagulant therapy has not been withheld.
  • Have emergency equipment readily available.
  • Instruct the patient to cooperate fully and to follow directions. Direct the patient to breathe normally and to avoid unnecessary movement.
  • Observe standard precautions, and follow the general guidelines in Patient Preparation and Specimen Collection. Positively identify the patient, and label the appropriate tubes with the corresponding patient demographics, date, and time of collection. Collect the specimen in four plastic conical tubes.
  • Record baseline vital signs, and assess neurological status.
  • To perform a lumbar puncture, position the patient in the knee-chest position at the side of the bed. Provide pillows to support the spine or for the patient to grasp. The sitting position is an alternative. In this position, the patient must bend the neck and chest to the knees.
  • Prepare the site—usually between L3 and L4, or between L4 and L5—with povidone-iodine and drape the area.
  • A local anesthetic is injected. Using sterile technique, the HCP inserts the spinal needle through the spinous processes of the vertebrae and into the subarachnoid space. Needle size has been shown to play a significant role in predictable incidence of post-puncture headache. However, the smaller the bevel, the more time is required to collect a sufficient volume of fluid; usually a 22 g needle is used. The stylet is removed. If the needle is properly placed, CSF drips from the needle.
  • Attach the stopcock and manometer, and measure initial pressure. Normal pressure for an adult in the lateral recumbent position is 60–200 mm H2O, and 10–100 mm H2O for children less than 8 yr. These values depend on the body position and are different in a horizontal than in a sitting position.
  • CSF pressure may be elevated if the patient is anxious, holding his or her breath, or tensing muscles. It may also be elevated if the patient’s knees are flexed too firmly against the abdomen. CSF pressure may be significantly elevated in patients with intracranial tumors or space occupying pockets of infection as seen in meningitis. If the initial pressure is elevated, the HCP may perform Queckenstedt’s test. To perform this test, pressure is applied to the jugular vein for about 10 sec. CSF pressure usually rises rapidly in response to the occlusion and then returns to the pretest level within 10 sec after the pressure is released. Sluggish response may indicate CSF obstruction.
  • Obtain four (or five) vials of fluid, according to the HCP’s request, in separate tubes (1 to 3 mL in each), and label them numerically (1 to 4 or 5) in the order they were filled.
  • A final pressure reading is taken, and the needle is removed. Clean the puncture site with an antiseptic solution and apply direct pressure with dry gauze to stop bleeding or CSF leakage. Observe/assess puncture site for bleeding, CSF leakage, or hematoma formation and secure gauze with adhesive bandage.
  • Promptly transport the specimen to the laboratory for processing and analysis.

Post-Test

  • Inform the patient that a report of the results will be made available to the requesting HCP, who will discuss the results with the patient.
  • Monitor vital signs and neurological status and for headache every 15 min for 1 hr, then every 2 hr for 4 hr, and then as ordered by the HCP. Monitor temperature every 4 hr for 24 hr. Compare with baseline values. Notify the HCP if temperature is elevated. Protocols may vary among facilities.
  • Administer fluids if permitted, especially fluids containing caffeine, to replace lost CSF and help prevent or relieve headache, which is a side effect of lumbar puncture. Advise the patient that headache may begin within a few hours up to 2 days after the procedure and may be associated with dizziness, nausea, and vomiting. The length of time for the headache to resolve varies considerably.
  • Observe/assess the puncture site for leakage, and frequently monitor body signs, such as temperature and blood pressure. Position the patient flat, either on the back or abdomen following the HCP’s instructions; some HCPs allow 30 degrees of elevation. Maintain this position for 8 hr. Changing position is acceptable as long as the body remains horizontal. Observe/assess the patient for neurological changes, such as altered level of consciousness, change in pupils, reports of tingling or numbness, and irritability.
  • Recognize anxiety related to test results. Discuss the implications of abnormal test results on the patient’s lifestyle. Provide teaching and information regarding the clinical implications of the test results, as appropriate.
  • Reinforce information given by the patient’s HCP regarding further testing, treatment, or referral to another HCP. Provide information regarding vaccine-preventable diseases when indicated (encephalitis, influenza, meningococcal diseases). Answer any questions or address any concerns voiced by the patient or family.
  • Instruct the patient in the use of any ordered medications. Explain the importance of adhering to the therapy regimen. As appropriate, instruct the patient in significant side effects and systemic reactions associated with the prescribed medication. Encourage him or her to review corresponding literature provided by a pharmacist.
  • Depending on the results of this procedure, additional testing may be performed to evaluate or monitor progression of the disease process and determine the need for a change in therapy. Evaluate test results in relation to the patient’s symptoms and other tests performed.

Related Monographs

  • Related tests include CBC, CT brain, culture for appropriate organisms (blood, fungal, mycobacteria, sputum, throat, viral, wound), EMG, evoked brain potentials, Gram stain, MRI brain, PET brain, and syphilis serology.
  • Refer to the Immune and Musculoskeletal systems tables at the end of the book for related tests by body system.
References in periodicals archive ?
This limitation emphasizes an important teaching point: for all patients with encephalitis, a portion of CSF should be saved for future analyses and, if an etiology is not found in the initial CSF analysis, then less common but possible etiologies, such as HMPV, should be tested for with saved CSF.
Thirtytwo patients had CSF analysis for WNV IgM, and 19 had detectable CSF WNV IgM antibodies.
Furthermore, laboratory CSF analysis is a cost consideration in resource-limited settings.
The diagnostic standard of care for MS includes CSF analysis using the OCB test alongside a comprehensive set of clinical tests to rule-out other neurological diseases.
A compressive cause of TM was excluded with thoracic and lumbar MRI and multiple sclerosis was excluded with cranial MRI and CSF analysis which revealed no abnormalities suggestive of multiple sclerosis.
The investigative methods (EEG, CSF analysis, and cranial MRI) were carried out as soon as the patients were hospitalized (four patients within 1 month, three patients within 1 to 3 months, and three patients at 3 to 6 months of the disease).
A second CSF analysis was performed on day 20 of admission; all parameters (biochemical analysis, direct microscopy, specific and nonspecific cultures, oligoclonal band, IgG index were within normal limits and PCR for HSV and JC virus were negative.
1) Several automated cell counters usually used in clinical laboratories have been evaluated for their applicability in CSF analysis.
CSF analysis showed 52 WBC/hpf (PMNs = 20%, lymphocytes = 59%, monocytes = 21%), and 25 RBCs /hpf.
CSF analysis provides the opportunity to distinguish between viral, bacterial, and fungal causes of meningitis and encephalitis (see Table IV).
Following an introduction to basic concepts for clinicians, information is provided about procedures for CSF analysis, neurochemical examinations, evaluation of biopsies, and clinical applications of neuroimmunology, microbiology, virology, and neurogenetic tests.
CSF analysis showed normal cell count, glucose and proteins.