Microbiology Laboratory

CELL COUNT OF CSF SAMPLE

Written by MicroDok

AIM: To determine whether the cells found in a CSF specimen are pus cells or lymphocytes. And to count the white blood cells (WBC’s) present in the CSF.

MATERIAL/APPARATUS: CSF specimen, microscope, cover slip, improved neubauer chamber, Pasteur pipette or bulb pipette, Turk’s solution, test tube test tube rack.

METHOD/PROCEDURE:

  1. Assemble the improved neubauer chamber, making sure that both the chamber and cover slip are completely clean.
  2. Mix the CSF specimen. This is done by rotating the string used in obtaining it.
  3. Carefully fill the improved neubauer counting chamber with the CSF specimen, making sure not to allow the fluid to flow into the channels on each side of the chamber.
  4. Wait for about 2 minutes for the cells to settle.
  5. Focus the cells on the chamber under the microscope using the ×10 and ×40 objective lens. Make sure that the condenser iris of the microscope is sufficiently closed in order to give a good contrast.
  6. Count the cells in 4 of the large squares indicated with the letter ‘W as shown in the figure below.

NOTE: Use Turk’s solution to dilute bloody CSF specimen before filling the improved neubauer chamber. They are 2 ways to doing this dilution depending on the amount of the blood in the CSF.

  1. One in five dilutions (1:5): This dilution is made if the CSF specimen contains much blood. It is done by placing 4 drops of Turk’s solution plus 1 drop of the CSF specimen in a clean test tube.
  2. One in two dilutions (1:2): This dilution is made if the CSF specimen does not contain much blood. It is done by placing 1 drop of Turk’s solution plus 1 drop of the CSF specimen in a clean test tube.

NOTE: The essence of diluting a bloody CSF specimen before performing any analysis on it is to ‘lyse/breakdown the red blood cells (RBC’s) in the specimen ’. The RBC’s makes it unsuitable or difficult to count the white blood cells (WBC’s).

Improved Neubauer countingchamber

REPORTING OF THE RESULT:

Report the appearance of the CSF specimen based on whether it is cloudy, clear, purulent or bloody. Count the white blood cells in 5 of the large squares of the improved neubauer chamber as shown in the diagram above, and report the number of cells by multiplying the number of WBC’s counted with the number of dilution made.  An example on how to do this is as follows:

  • For 1 in 2 CSF dilutions: If for example you counted 200 WBC’s, it will be 200 × 2 = 400.

Report the cell count as: 400 × 106 cell/mm3

  • For 1 in 4 CSF dilutions: If for example you counted 80 WBC’s, it will be 80 × 4 = 320.

Report the cell count as: 320 × 106 cell/mm3/

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MicroDok

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