Reticulated Platelets in Medicine: Current Evidence and Further Perspectives

Abstract

Reticulated platelets (RPs) are young thrombocytes, newly released from the bone marrow. The identification and quantification of these cells remained difficult for decades due to a lack of standardized preanalytical and analytical methods. With the introduction of automated hematology analyzers in clinical routine, the determination of RPs, either as a total count or as a fraction, became more reliable, faster and more affordable. Currently, RPs are the focus of research in multiple clinical settings. In cardiovascular medicine, recent studies have focused on the relationship between RPs, coronary artery disease (CAD) and clinical outcomes, as well as the impact of RPs on the effects of antiplatelet therapy. Cohort studies showed increased levels of RPs in patients with acute coronary syndrome (ACS) or cardioembolic stroke. In patients with ACS, increased levels of RPs were also associated with an increased incidence of major ischemic cardiovascular events during follow-up. Further studies showed an association of levels of RPs with the antiplatelet response to less-potent P2Y12 inhibitors. In patients with paroxysmal atrial fibrillation undergoing pulmonary vein isolation, levels of RPs differed significantly depending on the achieved rhythm (sinus rhythm vs. recurrent atrial fibrillation). Levels of RPs appear to also be predictive for bleeding events in patients with various hematological diagnoses. Although no causal relationship has so far been proven, RP values have been associated with a large number of pathologies and clinical scenarios. This review summarizes the current evidence with regard to RPs and their potential diagnostic and prognostic value for noncardiovascular patients and for cardiovascular patients in particular. It describes further perspectives on how the testing of these cells might improve the treatment of cardiovascular patients.

Keywords: bleeding; cardiology; immature platelets; percutaneous interventions; reticulated platelets; thrombocytopenia.

Figure 1

Characteristics of immature platelets and their clinical significance. ACS = acute coronary syndrome; AF = atrial fibrillation; ASA = acetylsalicylic acid; RNA = ribonucleic acid.

Figure 2

Scatterplot of a Sysmex XN-series cell counter, measuring the immature platelet fraction (IPF) in the platelet fluorescence (PLT-F) channel using forward-scattered light (cell volume) against side fluorescence (nucleic acid amount). FSC = forward-scattered light; RBC = red blood cell; SFL = side fluorescence; WBC = white blood cell.