ISSN 2398-2985      

Hematology: platelet count

6guinea pig

Synonym(s): Thrombocyte


Overview

  • Formed from cytoplasmic remnants of megakaryocytes.
  • Megakaryocytes or other platelet precursors are rarely seen in peripheral blood; their appearance is an indication of neoplasia or other conditions. When this happens, automatic machines may misindentify megakaryocytes or megakaryocyte fragments for leukocytes.
  • Participate in hemostasis: responsible for the initial hemostatic plug to prevent hemorrhage after initial injury.
  • Much smaller cells than red blood cells.
  • Round to oval flate disks of cytoplasm with no nuclei. They are slightly irregular in shape and size.
  • Guinea pig platelets have been reported to have an irregular oval shape with a pale-staining peripheral zone surrounding a darker staining inner zone. However, this is not always easy to appreciate in blood smears.
  • The anucleated cytoplasm contains variable amounts of small purple granules on Romanowsky-stained blood films.
  • They can be found in clamps in blood films.
  • Large platelets (larger than erythrocytes) are rarely found and they indicate elevated thrombopoiesis.

Sampling

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Tests

Methodologies

Manual count

  • With commercial blood dilution system + standard Neubauer chamber gives accurate platelet count.
  • Most automatic counts are also checked manually on a smear.
  • On Romansowsky or supravitally stained smear:
    • Count platelets and WBCs over same oil immersion field (10-30 platelets per x 1000 field in normal rabbit).
    • 6-7 platelets per field = ~100 x 109/L (=~100x103/µL).
    • Check edges of smear for platelet clumping which → artificially low platelet counts.
Estimates only, considerable errors, but clinically useful.

Automated bood counter

  • Rapid but if platelet clumping occurs → low readings.

Technician (extrinsic) limitations

  • Clumping can occur when the blood collection has not been smooth, due to damage to the vascular walls and initiation of coagulation cascade. This can also result in some thrombocytosis (by increased production of thrombocytes) or thrombocytopenia (by inability to count clumped platelets).
  • Clumping also occurs when the process of blood collection takes a longer time, particularly with small veins such as the lateral saphenous vein. In these situations, coagulation starts inside the syringe unless we pre-heparinize the syringe prior to blood collection.This problem is less likely to occur when the blood sample is collected from the cranial vena cava.

Result Data

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Hein J & Hartmann K (2003) Reference ranges for laboratory parameters in guinea pigs. Tierarztliche Praxis Ausgabe Kleintiere Heimtiere 31 (6), 383-389 (in German) PubMed.

Other sources of information

  • Campbell T W & Ellis C K (2007) Avian and Exotic Hematology and Cytology. 3rd edn. Wiley-Blackwell. ISBN: 978-0813818115.

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