8-58
K factor = dilution factor x area factor x depth factor
K factor = 100 x 0.111 x 10
K factor = 111
- Report and record the results as WBCs/L in the logbook and on the laboratory request form.
Normal values:
Adult 4.0 to 11.0 x 10 (to the 9th power) WBCs/L
Newborn 10.0 to 30.0 x 10 (to the 9th power) WBCs/L
Lab Procedure: WBC Differential Count
18D Skills and Training ManualWhen: You need to count and classify the different types of WBCs; assay the morphology of RBCs and
WBCs; and estimate the number of platelets in the blood smear.
What You Need: A properly Wright’s stained blood smear, a tally counter, a microscope, immersion oil,
and a laboratory request form.
What To Do:
- Inspect the smear under low-power magnification and locate the thin area on the smear where there
is no overlapping of RBCs. - Switch to oil immersion (100x) for the count.
a. Identify and count 100 consecutive WBCs.
NOTE: If the WBC count is between 2.0 x 10^9 and 5.0 x 10^9 WBCs/L, classify 300 WBCs. When the
count is greater than 5.0 x 10^9 WBCs/L, classify 500 WBCs.
b. Record each cell type separately on the differential tally counter.
(1) Lymphocyte
(2) Monocyte
(3) Neutrophilic band
(4) Segmented neutrophil
(5) Eosinophil
(6) Basophil
c. Express the number of each cell counted as a percentage. - Identify and report morphological variations of WBCs/RBCs/platelets.
a. Rouleaux formation
b. Signs of immaturity
c. Hemoglobin variation
d. Size and shape
e. Staining characteristics and inclusions
f. Nucleated RBCs (NRBCs) are reported as number per 100 WBCs counted.
NOTE: The WBC count may have to be corrected if the number of NRBCs is
5 or more per 100 WBCs.
FORMULA: (#WBC/L x 100) divided by (100 + #NRBCs counted) = Corrected WBC/L. - Perform a qualitative platelet estimate.
a. Adequate–8 to 20 per oil immersion field.
b. Increased–greater than 20 per oil immersion field.
c. Decreased–less than 8 per oil immersion field. - Report and record the results on the laboratory request form.