Page 2630 - Hematology_ Basic Principles and Practice ( PDFDrive )

Chapter 162 Resources for the Hematologist e11

Platelet Count and Mean Platelet Volume
Summary points • Used to assess integrity of hematopoietic and hemostatic systems
Methodology a Automated hematology analyzer—flow cytometric or impedance methods
Specimen requirements Whole blood: EDTA
Indications Suspected thrombocytopenia or thrombocytosis
Reference range Table 162.28
Interpretation • Thrombocytopenia
• Primary marrow process: infiltration by tumor or fibrosis, bone marrow failure, marrow suppression (drugs, toxins,
infections), myelodysplasia
• Secondary consumptive or destructive process: immunologic destruction, hypersplenism, microangiopathy,
disseminated intravascular coagulopathy
• Thrombocytosis
• Primary: essential thrombocythemia
• Secondary: acute-phase reactant, splenectomy, iron deficiency
• MPV may increase in destructive processes when larger, immature platelets prevail
• MPV is elevated in hereditary macrothrombocytopenia (Bernard-Soulier syndrome, MYH9 disorders) and ITP
• MPV is low in Wiskott-Aldrich syndrome
Related tests Peripheral smear, complete blood count, platelet aggregometry
Interfering substances Clotted or hemolyzed sample; difficult or prolonged collections may activate platelets and artifactually decrease the count
a Platelet count may also be estimated by peripheral smear review (count platelets in five fields using a 100× oil-immersion lens, take the average count, and multiply by
15,000) or manually counted using phase contrast microscopy and a hemocytometer. Automated methods using a hematology analyzer are usually more accurate and
preferred.
EDTA, Ethylenediaminetetraacetic acid; ITP, immune thrombocytopenic purpura; MPV, mean platelet volume; MYH9, myosin heavy chain 9.

Immature Platelet Fraction
Summary points • Similar to reticulated platelet count by flow cytometry, but available on automated hematology analyzers
• Analogous to reticulocyte count for erythropoiesis, IPF assesses rate of thrombopoiesis, can help distinguish decreased
marrow production versus peripheral destruction as likely cause of thrombocytopenia
Methodology Automated hematology analyzer—flow cytometric method using light scatter and fluorescence dyes that stain RNA
Specimen requirements Whole blood: EDTA
Indications Aid in differential diagnosis of thrombocytopenia, assess marrow response after marrow injury, chemotherapy, or bone
marrow transplant
Reference range Table 162.29
Interpretation • Increased with increased platelet production as seen in thrombocytopenia due to peripheral destruction (ITP, TTP;
assuming normally functioning marrow)
• Rise in IPF occurs with marrow engraftment posttransplant; precedes a rise in platelet count by a couple of days
• Normal or decreased with impaired thrombopoiesis (bone marrow failure, suppression)
Increased in patients with macrothrombocytopenia
May be artifactually elevated with platelet clumping
Related tests Platelet count, mean platelet volume, complete blood count
Interfering substances Clotted or hemolyzed specimen
References Briggs C: Quality counts: New parameters in blood cell counting. Int J Lab Hematol 31:277, 2009.
Miyazaki K, Koike Y, Kunishima S, et al: Immature platelet fraction measurement is influenced by platelet size and is a
useful parameter for discrimination of macrothrombocytopenia. Hematology 20:587, 2015.
EDTA, Ethylenediaminetetraacetic acid; IPF, immature platelet fraction; ITP, immune thrombocytopenic purpura; RNA, ribonucleic acid; TTP, thrombotic thrombocytopenic
purpura.