10.7: Platelets

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: An image from the thicker section of a peripheral blood smear showing platelet satellitism around three neutrophils. 100x oil immersion. From MLS Collection, University of Alberta, https://doi.org/10.7939/R31Z4280R

: An image from a peripheral blood smear showing platelet satellitism around a neutrophil. 100x oil immersion. From MLS Collection, University of Alberta, https://doi.org/10.7939/R3F766P1H

: An image from a peripheral blood smear demonstrating platelet clumping. 100x oil immersion. From MLS Collection, University of Alberta, https://doi.org/10.7939/R3XD0RD0V

Notes: Platelets are cytoplasmic fragmentations from a megakaryocyte. Fragmentation occurs by the megakaryocyte demarcation membrane system.¹

Nucleus-to-Cytoplasm Ratio: N/A²

Nucleoli: N/A²

Nucleus: N/A²

Cytoplasm:^1,2

Light blue to colourless

Azurophilic granules present

% in Bone Marrow: N/A

% in Peripheral Blood: 7-25 per field (100x oil immersion field)

Reticulated Platelets

Immature platelets that contain an abundant amount of RNA.¹

Platelet Clumps and Satellitism

Platelet satellitism is a phenomenon that can occur in vitro when a blood sample is collected in an EDTA anticoagulant tube. Platelets adhere to neutrophils by an antibody mediated process and this results in falsely decreased platelet counts.^3,4

Platelet clumping can also occur when blood is collected in an EDTA tube. Platelets become activated and aggregate. EDTA causes some cell antigens to be unmasked and react with antibodies in the serum.^3,4

In both cases, the issue may be corrected when blood samples are collected in sodium citrate anti-coagulated tubes.^3,4

References:

1. Lynne Williams J. The Platelet. In: Clinical laboratory hematology. 3rd ed. New Jersey: Pearson; 2015. p. 144–53.

2. Rodak BF, Carr JH. Megakaryocyte maturation. In: Clinical hematology atlas. 5th ed. St. Louis, Missouri: Elsevier Inc.; 2017. p. 31-40.

3. Burns C, Dotson M. Hematology Procedures. In: Clinical laboratory hematology. 3rd ed. New Jersey: Pearson; 2015. p. 782-814.

4. Clark KS, Hippe TGl. Manual, semiautomated, and point-of-care testing in hematology. In: Rodak’s hematology clinical applications and principles. 5th ed. St. Louis, Missouri: Saunders; 2015. p.187-207.