Applications of Extended Platelet Profiles in Clinical Practice

Thrombocytopenia is a frequent complication of patients presenting emergently across the world for a wide array of etiologies. From patients who develop thrombocytopenia due to invasive neoplastic disease affecting the bone marrow to patients who develop immune complications secondary to the formation of auto-antibody responses that drive patients' platelet counts lower or even cause infection, these patients stress the clearest need for prompt tests to discern the more likely thrombocytopenic-inducing cause. It is in this setting that looking at other platelet variables easily obtainable from modern hematology analyzers has gained traction. One of the elements found in extended platelet profiles are immature platelets (youngest and newly released platelets), also known as reticulated platelets, which are readily measurable from a complete blood count. One of the advantages of obtaining these counts is that they represent the immediate response of the bone marrow to the thrombocytopenia and, depending on etiology inducing the thrombocytopenia, they also provide information on the marrow's response to therapeutic approaches. It is in this context that this review will present information of how these relatively novel platelet parameters can be used in clinical practice and how they can be a rapid gauge of the body's response to disease processes leading to platelet losses. Thrombocytopenias resulting from infection (sepsis, viremia), autoantibody formation (immune thrombocytopenia and immune-mediated thrombotic thrombocytopenic purpura), immune dysregulation (systemic lupus erythematosus), and iatrogenic (drug-induced) will be discussed and used to explain how these young platelet measurements can provide valuable clinical information.