Evaluation of LP Studies

Last updated: April 6, 2026, 10:47 PM Pacific Time (PDT)

Interactive teaching tool for interpreting CSF studies after lumbar puncture, including pleocytosis pattern, CSF glucose ratio, traumatic tap correction, and likely diagnoses.

All Meningitis Blood / SAH Inflammatory Add-on tests Back to Main Page

Interactive LP calculator

LP labs to order
Core labs
Optional labs
Cell count
Chemistry
Appearance and early tests
Clinical context

Calculated interpretation

Likely diagnoses or causes

Recommended next labs, imaging, and diagnostics

Flowchart

First pass
Interpret CSF by pressure, cells, glucose, protein, and blood
Start by identifying dangerous patterns: bacterial meningitis, HSV encephalitis, cryptococcal/TB/fungal meningitis, SAH, and spinal block/inflammatory patterns.
Bacterial pattern
  • High WBC, often neutrophilic
  • Low CSF:serum glucose ratio
  • High protein and high opening pressure
  • Gram stain/culture may be positive
Viral pattern
  • Lymphocytic pleocytosis
  • Normal glucose
  • Mild to moderate protein elevation
  • HSV PCR when encephalitis is possible
Blood / SAH
  • Bloody CSF can be traumatic tap or SAH
  • Xanthochromia supports SAH in the right context
  • Tube clearing is not fully reliable alone
Add-on tests
  • Cryptococcal antigen in immunocompromised host
  • AFB/TB PCR/culture for TB risk
  • Cytology/flow for malignancy concern
  • Oligoclonal bands/IgG index for demyelination concern