WBC Correction for the Presence of NRBCs

Correcting The Total WBC Count For The Presence of Nucleated Red Blood Cells NRBCs)

Principle

Correcting the total white blood cell count for the presence of nucleated red blood cells (NRBCs) is important for obtaining an accurate assessment of the true white blood cell count. Nucleated red blood cells are premature red blood cells that still contain their nuclei, and they can be mistaken for white blood cells in automated cell counting methods. In particular, the lymphocytes. The technologist will keep track of the number of NRBCs per 100 white blood cells while counting/differentiating cells on a blood smear. There are two possible ways this can be achieved, and both procedures will be included in this method. Many of the new modern analyzers are designed to differentiate NRBCs from white blood cells more accurately, reducing the need for manual correction.

Procedure

1. Counting NRBC’s while doing a manual WBC differential:
   1. Find a good morphology zone to begin your WBC differential.
   2. Begin differentiating WBC’s using the cell counter.
   3. While you are differentiating the WBC’s keep track of the NRBC’s in each field. Note: NRBC’s are RBC’s not WBCs, so they must be tallied up separately.
   4. When your WBC differential is completed and the NRBC’s identified and counted, you will have the number of NRBC’s per 100 WBC counted and differentiated.
   5. Use this NRBC count in your formula to correct the total WBC count. See formula example below.
2. Counting NRBC’s without doing a manual WBC differential:
   1. Find a good morphology zone to begin your WBC differential.
   2. With this method you are not differentiating the WBCs.
   3. Use one button on the cell counter to count all cells.
   4. Use a second button on the counter to count the RBCs.
   5. Once the WBC count reaches 100, stop the counting.
   6. You will have the number of NRBC’s per 100 WBC cells counted.
   7. Use this NRBC’s in count in your formula to correct the total WBC count.

Procedural Notes

1. Not all NRBC’s will interfere with the total WBC count.
2. Not staying in a reasonable morphology area may lead to erroneous results.
3. Counting small lymphocytes or other mononuclear cells as NRBCs will lead to erroneous results.
4. Not counting all NRBCs as they appear in each filed will lead to erroneous results.
5. Not using the formula properly will lead to erroneous results.
6. Report the corrected total WBC count in x 109/L.

QUALITY AND INTERPRETATION

Formula

WBC x 100

# NRBCs + 100

Example

A patient with a total WBC of 19.3 x 109/L has 36% NRBCs identified on the blood smear.

19.3 x 100 = 1930

36 +100 = 136

1930/136

= 14.2 x 109/L – (Corrected total WBC count)