Why are four tubes of cerebrospinal fluid (CSF) sample drawn in suspected meningitis and where is each sent?

Updated: Jul 16, 2019
  • Author: Rodrigo Hasbun, MD, MPH; Chief Editor: Michael Stuart Bronze, MD  more...
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After drawing the CSF sample, do the following with the tubes:

  • Tube 1 – Send to the chemistry laboratory for glucose and protein

  • Tube 2 – Send to the hematology laboratory for a cell count with differential

  • Tube 3 – Send to the microbiology and immunology laboratory

  • Tube 4 – Hold for a repeat cell count with differential, if needed (or for other subsequent studies not initially ordered)

Microbiology and immunology studies for tube 3 include the following:

  • Gram stain

  • Bacterial culture

  • Acid-fast bacillus (AFB) stain and tuberculosis cultures

  • India ink stain

  • Cryptococcal antigen testing

  • Fungal cultures, counterimmunoelectrophoresis (CIE), VDRL, and cryptococcal antigen, if indicated

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