Performing a Blood Smear
Posted: Wednesday, December 8th, 2021 | Updated: Wednesday, December 8th, 2021
Posted: Wednesday, December 8th, 2021 | Updated: Wednesday, December 8th, 2021
Sample Collection
Collecting blood and preserving the sample in an EDTA tube is the standard method used for the microscopic evaluation of blood. If the sample was refrigerated, let it warm up to room temperature before evaluation
Making a Blood Smear
Place a very small drop of blood on the microscope slide at one end. Use another slide to spread the sample at an approximate angle of 30 to 45 degrees. With practice, the smear will have a feathered edge that ends about halfway down the slide. Let the sample air dry and then stain using the Diff-Quik Method. Once stained and gently rinsed, let the slide air dry once more
Microscopic Evaluation
Briefly scan the slide at 10x to visualize any platelet clumping along the feathered edge and any noticeable microfilaria, rouleaux, or agglutination
Using the 40x power scan 5-10 fields to quickly estimate the number of WBC for a patient. Take the average number of WBC counted per field and multiply by 1,500-2,000. This will give you a WBC estimate per microliter. To perform a differential, count 100 WBC by scanning in a zig zag pattern through the smear. Note any nucleated RBC while doing so because high counts of nRBC may obscure the WBC machine counts. Once you've counted 100 WBC and have classified them as neutrophil, lymphocyte, monocyte, eosinophil, basophil, or band you may list them as a percentage of your total WBC estimate obtained earlier. You may then obtain your absolute value by taking your percentage and multiplying it by the WBC estimate
Using the 100x power, evaluate the platelets in the monolayer. Remember, only evaluate the platelets if clumping along the feathered edge wasn't observed earlier at 10x. Scan 5-10 fields and count the number of platelets seen in each field. Take the average of all fields and multiply by 10,000-15,000. This will give you a platelet estimate per microliter. Typically, the healthy patient will have 10-15 platelets per HPF. Note the morphology of WBC, RBC, and platelets using the 100x power. Look for any blood parasites at this objective as well. Typically the RBC count is estimated via hematocrit tube percentages. Manually counts may be done via a hemocytometer if desired
Collecting blood and preserving the sample in an EDTA tube is the standard method used for the microscopic evaluation of blood. If the sample was refrigerated, let it warm up to room temperature before evaluation
Making a Blood Smear
Place a very small drop of blood on the microscope slide at one end. Use another slide to spread the sample at an approximate angle of 30 to 45 degrees. With practice, the smear will have a feathered edge that ends about halfway down the slide. Let the sample air dry and then stain using the Diff-Quik Method. Once stained and gently rinsed, let the slide air dry once more
Microscopic Evaluation
Briefly scan the slide at 10x to visualize any platelet clumping along the feathered edge and any noticeable microfilaria, rouleaux, or agglutination
Using the 40x power scan 5-10 fields to quickly estimate the number of WBC for a patient. Take the average number of WBC counted per field and multiply by 1,500-2,000. This will give you a WBC estimate per microliter. To perform a differential, count 100 WBC by scanning in a zig zag pattern through the smear. Note any nucleated RBC while doing so because high counts of nRBC may obscure the WBC machine counts. Once you've counted 100 WBC and have classified them as neutrophil, lymphocyte, monocyte, eosinophil, basophil, or band you may list them as a percentage of your total WBC estimate obtained earlier. You may then obtain your absolute value by taking your percentage and multiplying it by the WBC estimate
Using the 100x power, evaluate the platelets in the monolayer. Remember, only evaluate the platelets if clumping along the feathered edge wasn't observed earlier at 10x. Scan 5-10 fields and count the number of platelets seen in each field. Take the average of all fields and multiply by 10,000-15,000. This will give you a platelet estimate per microliter. Typically, the healthy patient will have 10-15 platelets per HPF. Note the morphology of WBC, RBC, and platelets using the 100x power. Look for any blood parasites at this objective as well. Typically the RBC count is estimated via hematocrit tube percentages. Manually counts may be done via a hemocytometer if desired
Sources:
Lee, Justine. "How Do I Make a Good Blood Smear? The How To of Blood Smears!" VetGirl Veterinary CE Blog, February 2013, https://vetgirlontherun.com/veterinary-continuing-education-how-to-make-blood-smear-veterinary-vetgirl-blog/
Lee, Justine. "How Do I Make a Good Blood Smear? The How To of Blood Smears!" VetGirl Veterinary CE Blog, February 2013, https://vetgirlontherun.com/veterinary-continuing-education-how-to-make-blood-smear-veterinary-vetgirl-blog/