Platelets: The Few, the Young, and the Active

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Key points

  • Many cell counters use novel approaches, ranging from the use of fluorescent dyes to monoclonal antibodies, to improve the accuracy and precision of the platelet count in patients with severe thrombocytopenia.

  • The determination of the percentage of immature platelets (immature platelet fraction) can be helpful in the determination of the underlying cause of a low platelet count.

  • Several companies are developing new cell counters based on digital image analysis; these instruments may allow better

History of platelet counting techniques

Platelet size initially eluded them to being included in the early automated technology. However, this has now been overcome by setting thresholds for different cells; there is now a reference method for platelet counting recommended by both the International Council for Standardization in Haematology (ICSH) and the International Society for Laboratory Hematology.6

Historically, through the 1970s, manual platelet counts were common practice. The method using a Neubauer hemocytometer and red cell

The Few

Achieving accurate PLTs at the low level, that is, less than 20 to 30 × 109/L, is essential in preventing spontaneous bleeding and in reducing the need for platelet transfusions.

Regular daily prophylactic platelet transfusion is the standard of care for patients with severe thrombocytopenia. The usual threshold is set for counts of 5 to 20 × 109/L in patients who have no clinical signs of bleeding and are apyrexial nonseptic, and on whom no invasive procedure is planned for the next 24 to

Mean platelet volume

All current automated hematology analyzers produce the MPV parameter. The normal range varies between 7–12 fL, although this parameter has not been standardised. Recently released platelets are larger and haemostatically more active. Platelet activation leads to changes in platelet shape and an increase in platelet swelling (sphering) resulting in an increased MPV. With impedance analyzers the MPV and PDW are derived from the platelet distribution curve and therefore should be interpreted

Future developing technology

Although currently in development for point of care (POC), image analysis could become the standard practice within diagnostic automated laboratories during the twenty-first century. Moving away from impedance or flow technology, these technologies incorporate image analysis. The main challenge for image analysis technology is in obtaining a single layer of cells to enable the cells to be captured for identification. A fixed volume of blood is used; thousands of images are captured; and using

Summary

The PLT has been incorporated in to the routine CBC for more than 50 years. Technology is rapidly evolving so that the accuracy and precision of the PLT, particularly in severe thrombocytopenic patients, has improved greatly. This improvement allows a more established set of rules for giving prophylactic and therapeutic platelet transfusions. Additional useful platelet parameters have become available, including MPV and rPLTs, which aid in the diagnostic and management decisions. In the future,

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Cited by (22)

  • Biological variation of platelet parameters determined by the Sysmex XN hematology analyzer

    2017, Clinica Chimica Acta
    Citation Excerpt :

    Several studies have been published on the potential diagnostic applications of platelet indices. Variations of MPV and/or PDW have been associated with an increased risk of developing cardiovascular, inflammatory and autoimmune diseases [1,2,6], whereas an enhanced P-LCR value has been frequently observed in association with anti-platelets antibodies [1–4,6,7]. The IPF parameter was found to be useful for differential diagnosis between thrombocytopenia due to decreased production or increased peripheral destruction, as well for evaluation of bone marrow and platelet recovery after hematopoietic stem cell transplantation [5,8].

  • Assessment of blood sample stability for complete blood count using the Sysmex XN-9000 and Mindray BC-6800 analyzers

    2016, Revista Brasileira de Hematologia e Hemoterapia
    Citation Excerpt :

    Notably, the latest generation of hematological analyzers provides a number of innovative quantitative and qualitative parameters, such as the enumeration of high fluorescence mononuclear cells (HFC)5–7 and nucleated red blood cell (NRBC) count,7 and the RBC distribution width expressed as a standard deviation (RDW-SD) or coefficient of variation (RDW-CV).8 Moreover, they may provide platelet distribution width (PDW), plateletcrit (PCT), mean platelet volume (MPV), percentage of large platelet (P-LCR) parameters,5,9,10 along with the reticulocyte count (RET) and immature reticulocyte fractions [IRF, high-fluorescence (HFR), middle-fluorescence (MFR) and low-fluorescence reticulocytes (LFR)], all of which are useful for the diagnosis and classification of anemia or for monitoring bone marrow erythropoiesis.11,12 The importance of verifying the stability of the aforementioned parameters is now unquestionable and published data about blood sample stability before analysis is scarce for the new generation of hematological analyzers.

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Financial Disclosure and Conflicts of Interest Obligations: S.J. Machin and C. Briggs have received an unrestricted educational grant from Sysmex in recent years.

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