Clinical Pathology: Hematology & Coagulation, Transfusion Medicine

• The gold standard method for counting platelets is the Neubauer chamber manual counting method. However, it is an imprecise method with high intra- and inter-operator variability.

• The Fonio method for estimating platelets is based on review of a peripheral blood smear using a light microscope. Using a ×10 ocular and ×100 objective lens, the average number of platelets per high power field (HPF) can be determined. The platelet estimate is [(20) × (average number of platelets per HPF)].

• If there are 10 platelets per HPF, then the platelet estimate using the Fonio method would be 200 × 109/L.

• Modern hematology analyzers measure the platelet count using impedance, optical, fluorescence, or antibody-based methods.

• Automated analyzers are more accurate, reproducible, and less labor intensive than manual methods.

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