Cerebrospinal Fluid Analysis Guidelines

Standard CSF Analysis Components

The American College of Critical Care Medicine recommends that CSF analysis should include cell counts with differential, glucose and protein concentrations, Gram stain, and bacterial cultures as the standard panel for all suspected central nervous system infections, with additional specialized tests determined by clinical context 1, 2
Normal CSF protein is typically less than 220 mg/dL, with elevated levels suggesting infection or inflammation, as suggested by the Critical Care Medicine guidelines 1, 2
Normal CSF glucose should be greater than 35 mg/dL with a CSF-to-blood glucose ratio greater than 0.23; lower values suggest bacterial infection, according to the Critical Care Medicine guidelines 1, 2
The Critical Care Medicine guidelines recommend that CSF opening pressure should be measured when clinically indicated, with normal pressure excluding meningitis in immunologically normal hosts 2
Cell count with differential is essential for all CSF analyses, as recommended by the Critical Care Medicine guidelines 1, 2
Bacterial meningitis typically presents with 2,000 total WBCs/μL or 1,180 neutrophils/μL, according to the Critical Care Medicine guidelines 2
Viral meningitis typically shows mild to moderate lymphocytic pleocytosis (5-1000 cells/μL), as suggested by the Clinical Infectious Diseases guidelines 4

For suspected bacterial meningitis, the Critical Care Medicine guidelines recommend Gram stain, culture, and antimicrobial susceptibility testing 1, 2
For suspected viral encephalitis/meningitis, the Clinical Infectious Diseases guidelines recommend PCR for herpes simplex virus, enterovirus, and other viruses based on epidemiology 4, 2
For immunocompromised patients, the Critical Care Medicine guidelines recommend additional testing for cryptococcal antigen, fungal stains/cultures, acid-fast bacilli, and PCR for opportunistic pathogens (CMV, JC virus, West Nile virus) 1, 2
For suspected neurosyphilis, the Clinical Infectious Diseases guidelines recommend CSF VDRL or RPR testing 4

For suspected multiple sclerosis, the Clinical Infectious Diseases and Alzheimer's and Dementia guidelines recommend oligoclonal bands, IgG index, and IgG synthesis rate 4, 5
For suspected Alzheimer's disease, the Alzheimer's and Dementia guidelines recommend Aβ42 and tau/phosphorylated tau (p-tau) profiles when diagnostic uncertainty remains after structural imaging 6
CSF biomarkers for AD are more useful in early or atypical presentations when diagnostic confidence is intermediate, as suggested by the Alzheimer's and Dementia guidelines 6

For patients with ventriculostomy catheters who develop fever or signs of meningitis, the Critical Care Medicine guidelines recommend that the catheter should be removed and the tip cultured 1, 2
In patients with shunt systems or Ommaya reservoirs, the Critical Care Medicine guidelines recommend that CSF should be obtained from the reservoir 2
When CSF flow to the subarachnoid space is obstructed, the Critical Care Medicine guidelines recommend considering obtaining samples from both the device and lumbar space 2

The presence of a normal opening pressure, fewer than 5 WBCs/μL, and normal protein concentration essentially excludes meningitis in immunocompetent hosts, as suggested by the Critical Care Medicine guidelines 2
Interpretation of AD CSF biomarkers requires consideration of pretest probability, age, clinical presentation, and possibility of multiple pathologies, according to the Alzheimer's and Dementia guidelines 6
False-positive results on imaging studies (CT, MRI, PET) may occur due to immune deficiency-related lymphoid hyperplasia or opportunistic infections in immunocompromised patients, as suggested by the Annals of Oncology guidelines 8