Method for performing a blood count and determining the morphology of a blood smear
A method for counting blood cells in a sample of whole blood. The method comprises the steps of: (a) providing a sample of whole blood; (b) depositing the sample of whole blood onto a slide, e.g., a microscope slide; (c) employing a spreader to create a blood smear; (d) allowing the blood smear to dry on the slide; (e) measuring absorption or reflectance of light attributable to the hemoglobin in the red blood cells in the blood smear on the slide; (f) recording a magnified two-dimensional digital image of the area of analysis identified by the measurement in step (e) as being of suitable thickness for analysis; and (g) collecting, analyzing, and storing data from the magnified two-dimensional digital image. Optionally, steps of fixing and staining of blood cells on the slide can be employed in the method.
1. A method for counting a plurality of blood cells in a sample of whole blood having a volume, said method comprising the steps of:
(a) depositing the sample of whole blood onto a slide;
(b) employing a spreader to create a blood smear;
(c) allowing the blood smear to dry on the slide;
(c) measuring an absorbance or a reflectance value of light attributable to hemoglobin in a plurality of red blood cells in each of a plurality of sections of the blood smear on the slide to determine an optical density for each of the sections of the blood smear;
(e) determining an optical density of the entire blood smear;
(f) recording a magnified two-dimensional digital image of an area of analysis identified by the measurement in step (d) as being of suitable thickness for analysis;
(g) counting a plurality of blood cells in the area of analysis;
(h) determining a volume of the sample that is present in the area of analysis by calculating a ratio of the optical density of the area of analysis to the optical density of the entire blood smear and multiplying said ratio by the volume of the sample; and
(i) collecting, analyzing, and storing data from the two-dimensional digital image to count the plurality of blood cells in the sample.
2. The method of claim 1 , further comprising fixing and staining the blood cells on the slide.
3. The method of claim 1 , wherein the volume of the sample of whole blood is known.
4. The method of claim 1 , wherein the volume of the sample of whole blood is determined by calculating a hemoglobin content from the optical density of the entire blood smear, and by multiplying said hemoglobin content by a measurement of a hemoglobin concentration per unit volume that is calculated at the point of aspiration of the sample.
5. The method of claim 1 , wherein the plurality of blood cells counted in the area of analysis are white blood cells.
6. The method of claim 1 , wherein the plurality of blood cells counted in the area of analysis are platelets.
7. The method of claim 1 , wherein the plurality of blood cells counted in the area of analysis are red blood cells.
8. The method of claim 1 , further comprising analyzing the two-dimensional digital image to determine a complete blood count for the sample.
9. The method of claim 1 , wherein measuring an absorbance or a reflectance value of light attributable to hemoglobin comprises determining whether the absorbance or reflectance value is below an upper cut-off value and above a lower cut-off value.
10. The method of claim 1 , wherein the two-dimensional digital image is a low power digital image.
11. The method of claim 1 , wherein the two-dimensional digital image is a high power digital image.