CSF interpretation

  • PIC logo
    PIC Endorsed
  • See also

    Meningitis and encephalitis
    Meningococcal disease
    Lumbar puncture
    Antimicrobial guidelines

    Key points

    1. If CSF is abnormal, the safest option is to commence empiric antimicrobial treatment for bacterial meningitis
    2. CSF parameters vary with age, which influences how a sample is interpreted
    3. The presence of any neutrophils in the CSF, regardless of age, may indicate bacterial meningitis. Discussion with a senior clinician is recommended
    4. In the case of a traumatic tap, interpret CSF results with caution. Do not rely on correcting the CSF white cell count for the number of red cells

    Background

    • Meningitis can occur in children with normal CSF microscopy
    • If there is a high clinical suspicion of meningitis or encephalitis, children who have a normal CSF microscopy should still be treated with IV antimicrobials, pending cultures or PCR
    • CSF white cell count and protein level are higher at birth and fall in the first 2 weeks of life       

    Assessment

    Normal values

     

    White cell count

     

    Age

    Neutrophils (x 106/L)

    Lymphocytes (x 106/L)

    Protein (g/L)

    Glucose
    CSF:blood ratio (total)

    Lactate
    (mmol/L)

      <1 month

    0#

      <22

    <1.0

    ≥0.6
    (or ≥2.0 mmol/L)

    0.9-2.5

     >1 month

    0

      ≤5

    <0.4

     ≥0.6
    (or ≥2.5 mmol/L)

    1.0-2.0

    Note: # Some studies have found that up to 5% of white blood cells in the CSF of neonates without meningitis, comprise neutrophils

    Interpretation of abnormal results

     

    White cell count

     

    Neutrophils
    (x 106/L)

    Lymphocytes
    (x 106/L)

    Protein
    (g/L)

    Glucose
    (CSF:blood ratio)

    Lactate
    (mmol/L)

    Bacterial meningitis

    100-10,000*

    <100

    >1.0*

    <0.4*

    >2.0*
    (>4.0 is strongly predictive of bacterial meningitis)

    Viral meningitis

    <100

     10-1000*

     0.4-1.0*

    Usually normal

    <2.0

    TB meningitis

    <100

    50-1000*

    1.0-5.0*

    <0.3*

    >2.0

    Note: *may be normal

    • Gram stain may be negative in up to 60% of cases of bacterial meningitis, even without prior antibiotics
    • A predominance of lymphocytes does not exclude bacterial meningitis
    • Neutrophils may predominate in viral meningitis, even after the first 24 hours
    • If the CSF is abnormal, the safest course is to treat for bacterial meningitis

    Other factors affecting results

    Antibiotics prior to lumbar puncture

    • Antibiotics are unlikely to significantly affect the CSF cell count or biochemistry if the CSF sample was taken within 24 hours of antibiotic administration
    • Prior antibiotics usually prevent the culture of bacteria from the CSF
    • Partially treated meningitis (ie if the child has recently been on oral antibiotics) may result in a lower CSF neutrophil count than untreated bacterial meningitis

    Seizures

    • Seizures do not cause an increased CSF cell count

    Traumatic (blood stained) tap

    • The safest interpretation of a traumatic tap is to count the total number of white cells and disregard the red cell count. If there are more white cells than the normal range for age, then the safest option is to commence empiric antibiotics
    • Some guidelines suggest that in traumatic taps, the white blood cell and protein count can be corrected based on the following calculation: 1 white blood cell for every 500-700 red blood cells and 0.01 g/L protein for every 1000 red cells
    • Consider subarachnoid haemorrhage when there are unexplained or persistently elevated red blood cells in CSF

    Time between sampling and analysis

    Delays in laboratory analysis of CSF can alter cell counts as a result of lysis in the CSF. There is progressive reduction in both neutrophils and lymphocytes after 4 hours

    Additional tests

    PCR

    • CSF PCR is widely available for Neisseria meningitidisStreptococcus pneumoniae, herpes simplex virus (HSV), enterovirus and parechovirus 
    • Some health services have access to extended PCR panels (eg Biofire®) which test for multiple bacteria, viruses and fungi (Escherichia coli, Haemophilus influenzae, Listeria monocytogenes, N meningitidis, Group B Streptococcus, S pneumoniae, cytomegalovirus, enterovirus, HSV-1, HSV-2, human herpesvirus-6, parechovirus, varicella zoster virus, Cryptococcus neoformans, Cryptococcus gattii)
    • Interpret with caution due to potential false positives, and correlate with CSF cell count
    • Do not delay empiric treatment while waiting for PCR results
    • Meningococcal PCR is particularly useful in patients with a clinical picture consistent with meningococcal meningitis, but who have received prior antibiotics
    • HSV PCR should be requested for patients with clinical features of encephalitis.  It may be negative in the first 36-72 hours of the illness. Consider repeating lumbar puncture and HSV PCR after this time if there is a high index of suspicion
    • Consider requesting enterovirus and parechovirus PCR on CSF from patients with clinical and/or CSF features of viral meningitis

    Bacterial antigens

    • CSF bacterial antigen tests have low sensitivity and specificity
    • They should therefore never influence treatment decisions and have little role if any in current management

    Consider consultation with local paediatric team 

    • All children with suspected encephalitis or bacterial meningitis
    • All children with concern for non-infectious encephalopathy

    Consider transfer when

    • Haemodynamic or respiratory instability
    • Altered conscious state, seizures or focal neurological signs
    • Child requiring care above the level of comfort of the local hospital
    • Complications of meningitis or encephalitis or poor response to treatment

    For emergency advice and paediatric or neonatal ICU transfers, see Retrieval services

    Parent information sheet

    Lumbar puncture
    Meningitis
    Meningococcal infection

    Last updated October 2024

  • Reference List

    1. Bhaskaran A, Racsa L, Gander R, Southern P, Cavuoti D, Alatoom A. Interpretation of positive molecular tests of common viruses in the cerebrospinal fluid. Diagn Microbiol Infect Dis. 2013
    2. Connell T, and Curtis N. How to interpret a CSF—the art and the science. Hot Topics in Infection and Immunity in Children II. Springer, Boston, MA. 2005
    3. Curtis GDW, Slack MPE, Tompkins DS. Cerebrospinal fluid lactate and the diagnosis of meningitis. 2005 https://www.sciencedirect.com/science/article/abs/pii/S0163445381913360 (viewed July 2024)
    4. Huy NT, Thao NT, Diep DT, Kikuchi M, Zamora J, Hirayama K. Cerebrospinal fluid lactate concentration to distinguish bacterial from aseptic meningitis: a systemic review and meta-analysis. Crit Care. 2010 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3220013/ (viewed July 2024)
    5. Kestenbaum LA et al. Defining cerebrospinal fluid white blood cell count reference values in neonates and young infants. Pediatrics 125.2, 2010
    6. Leen WG, Willemsen MA, Wevers RA, Verbeek MM. Cerebrospinal fluid glucose and lactate: age-specific reference values and implications for clinical practice. PLoS One. Epub 2012 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3412827/ (viewed July 2024)
    7. Lyons TW et al. Correction of cerebrospinal fluid protein in infants with traumatic lumbar punctures. The Pediatric infectious disease journal 36.10 (2017): 1006
    8. Shah SS et al. Age‐specific reference values for cerebrospinal fluid protein concentration in neonates and young infants. Journal of hospital medicine 6.1, 2011
    9. Thomson J et al. Cerebrospinal fluid reference values for young infants undergoing lumbar puncture. Pediatrics 141.3, 2018
    10. Uptodate, Sexton DJ, Richie M, Stout M. Cerebrospinal fluid: Physiology, composition, and findings in disease states. https://www.uptodate.com/contents/cerebrospinal-fluid-physiology-composition-and-findings-in-disease-states (viewed July 2024)