PlateletIndizes

PlateletIndizes, or platelet indices, are hematology parameters derived from automated complete blood counts that describe platelet size, volume, and distribution. The main indices are mean platelet volume (MPV), platelet distribution width (PDW), plateletcrit (PCT), and the platelet large cell ratio (P-LCR). These indices provide information about platelet production in the bone marrow and platelet activation and turnover.

MPV is the average size of circulating platelets, while PDW reflects the variation in platelet size within a sample. PCT expresses the volumetric fraction of blood occupied by platelets, analogous to hematocrit for red cells, and P-LCR indicates the proportion of large platelets. These indices are calculated or derived from measurements by hematology analyzers using impedance or optical methods. Values can vary depending on the analyzer model and preanalytic factors such as sample handling.

Interpretation of platelet indices is context-dependent. MPV tends to be higher when platelets are produced rapidly or released as larger, younger, or activated cells; a high PDW suggests a broader distribution of platelet sizes. A high P-LCR indicates a greater presence of large platelets. In cases of thrombocytopenia or thrombocytosis, these indices can support assessment but are not definitive diagnostic tests; they should be interpreted alongside the complete blood count and clinical information.

Preanalytical considerations are important, as EDTA-induced platelet swelling can artificially alter MPV if samples are stored too long before analysis. Ideal measurement is prompt after collection, and different anticoagulants can yield different values. Reference ranges vary by analyzer and laboratory.

Clinically, platelet indices are used as supplementary data in evaluating bleeding disorders, platelet production abnormalities, and certain cardiovascular risk assessments. They are best interpreted as part of a broader diagnostic context.