Corrected CSF WBC for Blood Contaminated CSF
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CSF WBC's (Measured) (/mm^3)
CSF RBC's (Measured) (/mm^3)
Blood WBC's (/mm^3)
Blood RBC's (x 10^6/mm^3 )
R e s u l t s
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Corrected WBC's
 
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Corrected CSF WBC for Blood Contaminated CSF

When performing a Lumbar Puncture (LP) to obtain Cerebrospinal Fluid (CSF); it is not uncommon for some peripheral blood to mix with (contaminate) the CSF.

In such cases, the actual WBC's in the CSF can be corrected by deducting the contribution of the contamination.

The formula is:

Corrected WBC's in CSF = Measured WBC's CSF - [(BWBC * CSFRBC)/(BRBC)]

  • Corrected WBC's in CSF are reported in WBC's/mm 3
  • Measured WBC's in CSF are reported in WBC's/mm 3
  • BWBC = WBC's in peripheral blood/mm 3
  • CSFRBC = RBC's found in CSF/mm 3
  • BRBC = RBC's in peripheral blood in cells/mm 3

As an example to demonstrate implementation of the formula, on a given patient with the following results:

  • CSF WBCs = 180/mm 3
  • CSF RBCs = 100,000 RBC's/mm 3
  • Blood WBC's = 4,500/mm 3
  • Blood RBC count = 4.6 million cells/mm 3

Corrected WBC's = 180-[(4,500 x 100,000)/(4,600,000)] = 82.2 cells/mm 3

Reference:
Body Fluid Analysis. In: Turgeon ML. Clinical Hematology. 4th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2005:399-436.