Comparison of Immature Platelet Count to Established Predictors of Platelet Reactivity During Thienopyridine Therapy

Immature platelet dynamics are associated with clinical outcomes after major trauma

BACKGROUND

Major trauma results in dramatic changes in platelet behavior. Newly formed platelets are more reactive than older platelets, but their contributions to hemostasis and thrombosis after severe injury have not been previously evaluated.

OBJECTIVES

To determine how immature platelet metrics and plasma thrombopoietin relate to clinical outcomes after major injury.

METHODS

A prospective observational cohort study was performed in adult trauma patients. Platelet counts and the immature platelet fraction (IPF) were measured at admission and 24 hours, 72 hours, and 7 days after injury. Thromboelastometry was performed at admission. Plasma thrombopoietin, c-Mpl, and GPIbα were quantified in a separate cohort. The primary outcome was in-hospital mortality; secondary outcomes were venous thromboembolic events and multiple organ dysfunction syndrome (MODS).

RESULTS

On admission, immature platelet counts (IPCs) were significantly lower in nonsurvivors (n = 40) than in survivors (n = 236; 7.3 × 109/L vs 10.6 × 109/L; P = .009), but IPF did not differ. Similarly, impaired platelet function on thromboelastometry was associated with lower admission IPC (9.1 × 109/L vs 11.9 × 109/L; P < .001). However, at later time points, we observed significantly higher IPF and IPC in patients who developed venous thromboembolism (21.0 × 109/L vs 11.1 × 109/L; P = .02) and prolonged MODS (20.9 × 109/L vs 11 × 109/L; P = .003) than in those who did not develop complications. Plasma thrombopoietin levels at admission were significantly lower in nonsurvivors (P < .001), in patients with MODS (P < .001), and in those who developed venous thromboembolism (P = .04).

CONCLUSION

Lower levels of immature platelets in the acute phase after major injury are associated with increased mortality, whereas higher immature platelet levels at later time points may predispose to thrombosis and MODS.

Platelet Reactivity in the Exacerbation of Psoriasis

Background: Psoriasis is a chronic, inflammatory, immune-mediated disease with a specific cutaneous presentation. Increased platelet aggregation has been observed in patients with extensive psoriatic lesions. The aim of this study was to evaluate the clinical factors affecting platelet reactivity in patients with an exacerbation of psoriasis. Methods: This was a prospective, single-center, observational study, enrolling patients hospitalized for an aggravation of psoriasis. Enrolled patients underwent single platelet function testing with light transmission aggregometry on the first morning of hospitalization. Results: 120 patients were enrolled in the study. Of the compared subgroups, women had higher maximal platelet aggregation (MPA) than men (77% vs. 72%; p = 0.03), and those with BMIs < 25 kg/m2 showed higher platelet reactivity compared to subjects with BMIs ≥ 25 kg/m2 (75% vs. 73%; p = 0.02). There was a positive correlation between MPA and platelet count (r = 0.27; p < 0.01), as well as C-reactive protein concentration (r = 0.20; p = 0.03), while a negative correlation was observed with total cholesterol (r = -0.24; p = 0.01) and triglycerides (r = -0.30; p < 0.01). A two-step analysis based on multidimensional models with random effects revealed that every increase in the platelet count by 103/μL led to an increase in MPA by 0.07% (R2 = 0.07; p < 0.01), and an increase in triglycerides' concentration by 1 mg/dL was related to a reduction in MPA by 0.05% (R2 = 0.07; p < 0.01). Conclusions: The increased platelet reactivity observed in patients with psoriasis appears to be multifactorial and related to several clinical and laboratory features. Further research is warranted to put these findings into a clinical perspective.

Correlation between baseline immature platelets fraction levels and peak troponin in patients with acute myocardial infarction

INTRODUCTION

Elevated peak cardiac troponin levels have been linked with increased morbidity and mortality in patients with acute myocardial infarction (AMI). Immature Platelets are young and relatively large platelets that are hyper-reactive and pro-thrombotic compared to regular platelets. Increased immature platelet fraction (IPF) has been associated with an elevated risk of thrombotic events. We hypothesize that patients with higher IPF levels during AMI, will experience a more severe infarct, leading to elevated peak troponin levels.

METHODS

Clinical data from patients admitted to the cardiology division between 2018 and 2022, who were diagnosed with AMI and underwent an IPF testing. Univariate and multivariate regression analyses were performed to identify predictors of elevated peak troponin.

RESULTS

Among the 277 patients diagnosed with AMI who underwent IPF testing, 113 had (STEMI) and 164 had (NSTEMI). The median value of IPF of 4.2% was used as the threshold for defining elevated IPF. Notably, among STEMI patients, those with IPF ≥ 4.2% had significantly higher peak troponin levels ( P  = 0.021). Conversely, no significant difference in peak troponin levels was observed among NSTEMI patients ( P  = 0.348). Multivariate analysis identified patients with STEMI in the higher IPF group as one of the significant predictors for elevated peak troponin levels.

CONCLUSION

This study revealed a correlation between higher baseline IPF levels and increased peak troponin levels specifically in STEMI patients, while no such association was found in NSTEMI patients. Incorporating IPF levels above the median into risk stratification scores for STEMI patients may provide valuable support for adopting a more proactive therapeutic approach.

Immature Platelet Fraction Predicts Adverse Events in Patients With Acute Coronary Syndrome: the ISAR-REACT 5 Reticulated Platelet Substudy

BACKGROUND

Immature or reticulated platelets are associated with impaired efficacy of antiplatelet drugs and adverse events in cardiovascular patients. Their role as a predictive biomarker in patients with acute coronary syndrome treated with potent P2Y₁₂ receptor inhibitors is not fully understood. We aimed to prospectively evaluate reticulated platelets as a predictor of the primary end point of the ISAR-REACT 5 trial consisting of death, myocardial infarction, or stroke at 1 year in patients with acute coronary syndrome randomized to prasugrel or ticagrelor.

METHODS

Immature platelet fraction (IPF) was assessed within 48 hours after randomization. Patients were divided based on the IPF median values: the IPF^high group included patients with IPF>median and the IPF^low group included patients with IPF≤median. Platelet aggregation was assessed using the Multiplate Analyzer and was correlated to IPF.

RESULTS

Five hundred seventy-seven patients were included in the study. IPF values in % (median [interquartile range]) within the first 48 hours did not differ between the two study groups: 3.6 (2.5-5.2)% in the prasugrel group and 3.6 (2.5-5.4)% in the ticagrelor group (P=0.882). The incidence of the primary end point was significantly higher in the IPF^high (IPF>3.6%) group compared with the IPF^low (IPF≤3.6%) group: 13.0% versus 7.2% (HR_adj, 1.74 [1.02-3.00]; P=0.044), independently from the assigned drug (P_int=0.159). No significant association between IPF and BARC 3 to 5 bleeding was observed. ADP-induced platelet aggregation correlated significantly with IPF in patients treated with prasugrel (r=0.22; P=0.005) while no correlation was detected in patients treated with ticagrelor (r=0.09; P=0.257).

CONCLUSIONS

Independently from drug treatment, IPF was associated with the primary end point and therefore is a promising biomarker for the prediction of adverse cardiovascular events in patients with acute coronary syndrome treated with prasugrel or ticagrelor.

REGISTRATION

https://www.

CLINICALTRIALS

gov; Unique identifier: NCT01944800.

Platelets in Myocardial Ischemia/Reperfusion Injury

Coronary artery disease, including myocardial infarction (MI), remains a leading cause of global mortality. Rapid reperfusion therapy is key to the improvement of patient outcome but contributes substantially to the final cardiac damage. This phenomenon is called "ischemia/reperfusion injury (IRI)." The underlying mechanisms of IRI are complex and not fully understood. Contributing cellular and molecular mechanisms involve the formation of microthrombi, alterations in ion concentrations, pH shifts, dysregulation of osmolality, and, importantly, inflammation. Beyond their known action as drivers of the development of coronary plaques leading to MI, platelets have been identified as important mediators in myocardial IRI. Circulating platelets are activated by the IRI-provoked damages in the vascular endothelium. This leads to platelet adherence to the reperfused endothelium, aggregation, and the formation of microthrombi. Furthermore, activated platelets release vasoconstrictive substances, act via surface molecules, and enhance leukocyte infiltration into post-IR tissue, that is, via platelet-leukocyte complexes. A better understanding of platelet contributions to myocardial IRI, including their interaction with other lesion-associated cells, is necessary to develop effective treatment strategies to prevent IRI and further improve the condition of the reperfused myocardium. In this review, we briefly summarize platelet properties that modulate IRI. We also describe the beneficial impacts of antiplatelet agents as well as their mechanisms of action in IRI beyond classic effects.

Impact of On-Clopidogrel Platelet Reactivity on Incidence of Peri-Interventional Bleeding in Patients Undergoing Transcatheter Aortic Valve Implantation

Dual anti-platelet therapy (DAPT) with clopidogrel and acetylsalicylic acid (ASA) has previously been recommended after transcatheter aortic valve implantation (TAVI) and is still the standard of care in patients who underwent coronary stent placement within 3 months prior to TAVI. This study sought to evaluate whether on-treatment platelet reactivity is a predictor for the occurrence of bleeding events after TAVI. This study enrolled 484 patients undergoing TAVI from November 2013 until April 2018. Patients were either on long-term DAPT with clopidogrel and ASA or received loading doses of both drugs before TAVI, reflecting the standard of care at the time of the patient’s enrollment. Platelet reactivity was determined by multi-electrode impedance aggregometry before TAVI, at days 1 and 5 thereafter. Peri-interventional bleeding was assessed up to 5 days following TAVI and coded according to BARC-classification. Bleeding events were seen in 199 (41.1%) patients. The most frequent were BARC 2 bleeding cases (24.2%), followed by BARC 1 (6.0%), BARC 3b (5.2%), and BARC 3a (4.5%) cases. Low on-clopidogrel platelet reactivity before TAVI was present in 243 patients, of which 44.4% had a bleeding event. In contrast, the incidence of bleeding was 30.5% in the 95 patients with high on-clopidogrel platelet reactivity. Multivariate logistic regression analysis identified low/normal/high on-clopidogrel platelet reactivity (OR: 0.533; CI: 0.309–0.917; p = 0.023) and use of oral anticoagulation (OR: 1.766; CI: 1.209–2.581; p = 0.003) as strongest predictors for peri-interventional bleeding events. These findings support current recommendations advocating against the routine use of dual antiplatelet therapy following TAVI.

Role of Reticulated Platelets in Cardiovascular Disease

Human platelets differ considerably with regard to their size, RNA content and thrombogenicity. Reticulated platelets (RPs) are young, hyper-reactive platelets that are newly released from the bone marrow. They are larger and contain more RNA compared to older platelets. In comparison to more mature platelets, they exhibit a significantly higher thrombogenicity and are known to be elevated in patients with an increased platelet turnover such as, diabetics and after acute myocardial infarction. Several studies have shown that RPs correlate with an insufficient antiplatelet response to aspirin and specific P2Y₁₂ receptor inhibitors. In addition, RPs are promising novel biomarkers for the prediction of adverse cardiovascular events in cardiovascular disease. However, the reason for RPs intrinsic hyper-reactivity and their association with ischemic events is not completely understood and the biology of RPs is still under investigation. We here present a structured review of preclinical and clinical findings concerning the role of RPs in cardiovascular disease.

Platelet Subtypes in Inflammatory Settings

In addition to their essential role in hemostasis and thrombosis, platelets also modulate inflammatory reactions and immune responses. This is achieved by specialized surface receptors as well as secretory products including inflammatory mediators and cytokines. Platelets can support and facilitate the recruitment of leukocytes into inflamed tissue. The various properties of platelet function make it less surprising that circulating platelets are different within one individual. Platelets have different physical properties leading to distinct subtypes of platelets based either on their function (procoagulant, aggregatory, secretory) or their age (reticulated/immature, non-reticulated/mature). To understand the significance of platelet phenotypic variation, qualitatively distinguishable platelet phenotypes should be studied in a variety of physiological and pathological circumstances. The advancement in proteomics instrumentation and tools (such as mass spectrometry-driven approaches) improved the ability to perform studies beyond that of foundational work. Despite the wealth of knowledge around molecular processes in platelets, knowledge gaps in understanding platelet phenotypes in health and disease exist. In this review, we report an overview of the role of platelet subpopulations in inflammation and a selection of tools for investigating the role of platelet subpopulations in inflammation.

Impact of high platelet turnover on the platelet transcriptome: Results from platelet RNA-sequencing in patients with sepsis

Background

Sepsis is associated with high platelet turnover and elevated levels of immature platelets. Changes in the platelet transcriptome and the specific impact of immature platelets on the platelet transcriptome remain unclear. Thus, this study sought to address whether and how elevated levels of immature platelets affect the platelet transcriptome in patients with sepsis.

Methods

Blood samples were obtained from patients with sepsis requiring vasopressor therapy (n = 8) and from a control group of patients with stable coronary artery disease and otherwise similar demographic characteristics (n = 8). Immature platelet fraction (IPF) was determined on a Sysmex XE 2100 analyser and platelet function was tested by impedance aggregometry. RNA from leukocyte-depleted platelets was used for transcriptome analysis by Next Generation Sequencing integrating the use of unique molecular identifiers.

Results

IPF (median [interquartile range]) was significantly elevated in sepsis patients (6.4 [5.3–8.7] % vs. 3.6 [2.6–4.6] %, p = 0.005). Platelet function testing revealed no differences in adenosine diphosphate- or thrombin receptor activating peptide-induced platelet aggregation between control and sepsis patients. Putative circular RNA transcripts were decreased in platelets from septic patients. Leukocyte contamination defined by CD45 abundance levels in RNA-sequencing was absent in both groups. Principal component analysis of transcripts showed only partial overlap of clustering with IPF levels. RNA sequencing showed up-regulation of 524 and down-regulation of 118 genes in platelets from sepsis patients compared to controls. Upregulated genes were mostly related to catabolic processes and protein translation. Comparison to published platelet transcriptomes showed a large overlap of changes observed in sepsis and COVID-19 but not with reticulated platelets from healthy donors.

Conclusions

Patients with sepsis appear to have a less degraded platelet transcriptome as indicated by increased levels of immature platelets and decreased levels of putative circular RNA transcripts. The present data suggests that increased protein translation is a characteristic mechanism of systemic inflammation.

Identification of Potential Biological Factors Affecting the Treatment of Ticagrelor After Percutaneous Coronary Intervention in the Chinese Population

Background

Generally, many individual factors can affect the clinical application of drugs, of which genetic factors contribute more than 20%. Ticagrelor is a new class of receptor inhibitors receptor antagonist of P2Y12 and is used as an antiplatelet agents. But it is not affected by the influence of CYP2C19 polymorphism. With lack of predicted biomarkers, especially the research data of Chinese, it has the important significance in studying individual differences of ticagrelor in the antiplatelet efficacy and safety, through pharmacogenomics research.

Methods

Whole-exome sequencing (WES) was performed in 100 patients after PCI with ticagrelor treatment. Clinical characteristics and WES of patients were used to performed genome-wide association analysis (GWAS), region-based tests of rare DNA variant to find the influencing factors of antiplatelet effect to ticagrelor and bleeding events. Co-expression, protein–protein interaction (PPI) network and pathway enrichment analysis were then used to find possible genetic mechanisms. Atlas of GWAS (https://atlas.ctglab.nl/) were used for external data validation.

Results

DNAH17, PGS1 and ABCA1 as the potential variant genes are associated with the expected antiplatelet effect to ticagrelor. The affected pathways may include the synthesis and metabolism of lipoprotein cholesterol and the catabolic process of pyrimidine-containing compound (GO:0072529). Age, sex and PLT were found may be potential factors for ticagrelor bleeding events.

Conclusion

We systematically identified new genetic variants and some risk factors for reduced efficacy of ticagrelor and highlighted related genes that may be involved in antiplatelet effects and bleeding event of ticagrelor. Our results enhance the understanding of the absorption and metabolic mechanisms that influence antiplatelet response to ticagrelor treatment.

Trial Registration

ClinicalTrials.gov Identifier: NCT03161002. First Posted: May 19, 2017. https://clinicaltrials.gov/ct2/show/study/NCT03161002.

Platelets contribute to disease severity in COVID-19

OBJECTIVE

Heightened inflammation, dysregulated immunity, and thrombotic events are characteristic of hospitalized COVID-19 patients. Given that platelets are key regulators of thrombosis, inflammation, and immunity they represent prime candidates as mediators of COVID-19-associated pathogenesis. The objective of this study was to understand the contribution of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) to the platelet phenotype via phenotypic (activation, aggregation) and transcriptomic characterization.

APPROACH AND RESULTS

In a cohort of 3915 hospitalized COVID-19 patients, we analyzed blood platelet indices collected at hospital admission. Following adjustment for demographics, clinical risk factors, medication, and biomarkers of inflammation and thrombosis, we find platelet count, size, and immaturity are associated with increased critical illness and all-cause mortality. Bone marrow, lung tissue, and blood from COVID-19 patients revealed the presence of SARS-CoV-2 virions in megakaryocytes and platelets. Characterization of COVID-19 platelets found them to be hyperreactive (increased aggregation, and expression of P-selectin and CD40) and to have a distinct transcriptomic profile characteristic of prothrombotic large and immature platelets. In vitro mechanistic studies highlight that the interaction of SARS-CoV-2 with megakaryocytes alters the platelet transcriptome, and its effects are distinct from the coronavirus responsible for the common cold (CoV-OC43).

CONCLUSIONS

Platelet count, size, and maturity associate with increased critical illness and all-cause mortality among hospitalized COVID-19 patients. Profiling tissues and blood from COVID-19 patients revealed that SARS-CoV-2 virions enter megakaryocytes and platelets and associate with alterations to the platelet transcriptome and activation profile.

Immature Platelet Fraction and COVID-19: Maturing prognostic links!

Prompted by the combination of an ever-evolving comprehension of the platelet activation as a pivotal perpetuator of an ongoing systemic inflammatory process and an encouraging literature on the prognostic role of immature platelet fraction (IPF) in septic and prothrombotic settings, we present an elaborated account of the possible prognostic links between IPF and Coronavirus disease 2019 (COVID-19).

Lower Antiplatelet Effect of Aspirin in Essential Thrombocythemia than in Coronary Artery Disease

Background  Patients with essential thrombocythemia (ET) and coronary artery disease (CAD) have increased risk of thromboembolic complications. In addition, a reduced antiplatelet effect of aspirin has been demonstrated in both patient groups. As ET is a platelet disorder, platelets may be more important for the thromboembolic risk in ET than in CAD. We aimed to investigate the antiplatelet effect of aspirin and platelet turnover in ET versus CAD patients.

Methods  We included 48 ET patients and an age-matched group of 48 CAD patients. The effect of aspirin was evaluated by thromboxane B ₂ (TXB ₂ ) levels and platelet aggregation. Platelet turnover was assessed by immature platelet count (IPC) and immature platelet fraction (IPF).

Results  ET patients had reduced effect of aspirin compared with CAD patients, demonstrated by significantly higher TXB ₂ levels (median of differences = 22.3 ng/mL, p  < 0.0001) and platelet aggregation (median of differences = 131.0 AU*min, p  = 0.0003). Furthermore, ET patients had significantly higher IPC ( p  < 0.0001) and IPF ( p  = 0.0004) than CAD patients.

Conclusion  ET patients have lower 24-hour antiplatelet effect of aspirin than CAD patients. This may be explained by an increased platelet production and turnover counteracting the antiplatelet effect of aspirin. These findings strengthen the rationale for exploring novel antiplatelet regimens in ET patients to reduce the risk of cardiovascular events.

Reticulated Platelets-Which Functions Have Been Established by In Vivo and In Vitro Data?

Reticulated platelets (RP) are the youngest platelet fraction released into the circulation. These immature platelets have increased RNA content, a larger cell volume, more dense granules, higher levels of surface activation markers and are thought to be more reactive compared to their mature counterparts. RP have been associated with cardiovascular disease, diabetes and increased mortality. Yet only a few animal studies investigating RP have been conducted so far and further investigations are warranted. Established methods to count RP are flow cytometry (staining with thiazole orange or SYTO13) or fully automated hematology analyzers (immature platelet fraction, IPF). IPF has been established as a diagnostic parameter in thrombocytopenia, cardiovascular disease and, in particular, the response to antiplatelet therapy. This review seeks to provide an overview of the key features of RP as well as preanalytical and analytical aspects that need to be considered when working with this platelet population.

Impact of gender on immature platelet count and its relationship with coronary artery disease

The impact of platelet parameters on the cardiovascular risk is still debated. Gender differences in platelet volume indexes and turnover have been previously reported, potentially conditioning their role in the development of coronary artery disease (CAD). However, few studies have addressed, so far, the impact of gender on the immature platelet fraction (IPF) and count (IPC) and their relationship with CAD. We enrolled consecutive patients undergoing coronary angiography in a single centre. IPF and platelet indexes were measured at admission. Significant CAD was defined as the presence of at least one coronary stenosis more than 50%. A total of 2550 patients were included, 1835 (72%) were males, and 715 (28%) were females. Female patients were older (p < 0.001), with lower BMI (p = 0.002), lower prevalence of active smoking (p < 0.001), previous MI, previous PCI and CABG (p = 0.001, p = 0.001, p < 0.001), whilst a higher prevalence of renal failure (p = 0.02), acute presentation (p < 0.001) and CAD (p < 0.001). Platelet count was higher in females (p < 0.001), as well as the IPC levels (838.38 ± 562.05 vs 792.24 ± 535.66, p = 0.05) with no difference in the levels of immature platelet fraction (3.67 ± 2.68% vs 3.74 ± 2.6%, p = 0.55) or the prevalence of patients with IPF ≥ 3rd tertile (33.7% vs 35.2%, p = 0.26). At multivariate analysis, after correction for baseline confounders, gender did not emerge as an independent predictor of higher IPF (adjusted OR [95% CI] = 0.82 [0.64-1.06], p = 0.13). When dividing our patients according to the levels of IPF, in women we observed an inverse association between IPF ≥ 3rd tertile and coronary calcifications (p = 0.025) and a higher prevalence of restenosis (p = 0.003), but no difference in CAD (65.6% vs 66.9%, p = 0.71) or severe CAD (28.1% vs 24.7%, p = 0.31). In males, the IPF ≥ 3rd tertile related with a lower TIMI flow (p = 0.001). Males with lower IPF had a significantly higher percentage of CAD (87.7% vs 83.3%, p = 0.007; adjusted OR: 0.699 [95% CI] = [0.54-0.91], p = 0.008) but not for severe CAD (36.5% vs 39.9%, p = 0.134). The present study shows that among patients undergoing coronary angiography, gender is not associated to the levels of immature platelet fraction. Moreover, we found no association between IPF and the prevalence and extent of CAD in female gender, whereas in male gender the IPF was inversely related with the prevalence of CAD.

Reticulated Platelets in Medicine: Current Evidence and Further Perspectives

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.

Immature platelets in patients hospitalized with Covid-19

Coronavirus disease 2019 (Covid-19) is associated with high incidence of venous and arterial thromboembolic events. Currently, there are no markers to guide antithrombotic therapy in Covid-19. Immature platelets represent a population of hyper-reactive platelets associated with arterial events. This prospective study compared consecutive Covid-19 patients (n = 47, median age = 56 years) to patients with acute myocardial infarction (AMI, n = 100, median age = 59 years) and a group of stable patients with cardiovascular risk factors (n = 64, median age = 68 years). Immature platelet fraction (IPF) and immature platelet count (IPC) were determined by the Sysmex XN-3000 auto-analyzer on admission and at subsequent time-points. IPF% on admission was higher in Covid-19 than the stable group and similar to the AMI group (4.8% [IQR 3.4-6.9], 3.5% [2.7-5.1], 4.55% [3.0-6.75], respectively, p = 0.0053). IPC on admission was also higher in Covid-19 than the stable group and similar to the AMI group (10.8 × 10⁹/L [8.3-18.1], 7.35 × 10⁹/L [5.3-10.5], 10.7 × 10⁹/L [7.7-16.8], respectively, P < 0.0001). The maximal IPF% among the Covid-19 group was higher than the stable group and similar to the AMI group. The maximal IPC in Covid-19 was higher than the maximal IPC in both the stable and AMI groups (COVID-19: 14.4 × 10⁹/L [9.4-20.9], AMI: 10.9 × 10⁹/L [7.6-15.2], P = 0.0035, Stable: 7.55 × 10⁹/L [5.55-10.5], P < 0.0001). Patients with Covid-19 have increased immature platelets indices compared to stable patients with cardiovascular risk factors, and as the disease progresses also compared to AMI patients. The enhanced platelet turnover and reactivity may have a role in the development of thrombotic events in Covid-19 patients.

Ultrastructural, transcriptional, and functional differences between human reticulated and non-reticulated platelets

BACKGROUND

Reticulated platelets (RP) are the youngest circulating platelets in blood. An increased amount of this subpopulation is associated with higher cardiovascular risk and mortality.

OBJECTIVES

It is unknown to what extent intrinsic properties of RP contribute to their hyperreactive features. This study is the first providing a multifactorial approach based on ultrastructural, transcriptional, and functional analysis of RP compared to non-RP sorted by flow cytometry.

METHODS

Reticulated platelets and non-RP were sorted after platelet staining with SYTO 13. Employing transmission electron microscopy, 1089 micrographs were analyzed for platelet size, amounts of intracellular structures, and anatomical surrogates indicating activation. Long and small RNA-sequencing (RNA-seq) were performed for analyzing differential gene expression. Functional analysis of P-selectin-an upregulated mRNA in RP-was performed in healthy subjects and patients on P2Y12 -inhibitors.

RESULTS

Electron micrographs uncovered distinct ultrastructural differences in RP versus non-RP. Cross sections were 1.9-fold larger in RP (P < .0001). Amounts of α-granules, dense granules, open canalicular system-openings, and mitochondria were increased in RP, which persisted after adjustment for platelet size. Long RNA-seq showed 1212 upregulated transcripts that are predominantly associated to platelet shape change, aggregation, and activation; 1264 mRNAs were downregulated in RP. Small RNA-seq did not reveal any differentially expressed transcripts. Functional analysis displayed higher P-selectin expression as compared to non-RP upon ADP- or TRAP-stimulation.

CONCLUSIONS

Our results demonstrate that altered intrinsic structural and molecular properties contribute to the hyperreactivity of RP. These properties and an increased amount of RP may account for the association with cardiovascular risk.

Influence of diagnosis of venous thromboembolism on immature platelets, absolute platelet count and platelet aggregation over time

The extent of the involvement of platelets in venous thromboembolisms (VTE) is still not fully understood. Immature platelets are large, RNA-rich, prothrombotic platelets. They are involved in arterial thromboembolisms and are associated with adverse cardiovascular events. Their role in VTE has not been investigated before. The aim of this study was to assess different platelet parameters including immature platelet fraction (IPF), immature platelet count (IPC), absolute platelet count and platelet aggregation (PA) over time in patients with VTE at time of diagnosis, as well as at 3-10 days and at 90-110 days after diagnosis. 50 healthy volunteers similar in age and sex to patients served as controls at diagnosis. IPF was measured by the Sysmex XE-5000 analyzer, PA was assessed using the Multiplate analyzer. Diagnosis of VTE had no relevant effect on IPF and IPC whereas absolute platelet count and PA were significantly decreased compared to controls. In the course of VTE, IPF decreased significantly, whereas IPC, absolute platelet count and PA increased. In conclusion, VTE was associated with relevant changes of the absolute platelet count and PA at diagnosis, as well as changes in IPF and IPC over time reflecting a relevant and measurable platelet consumption in VTEs.

Multicenter evaluation of analytical performances of platelet counts and platelet parameters: Carryover, precision, and stability

INTRODUCTION

The correctness of the results of automated platelet analysis is still highly debated. The aim of this multicenter study, conducted according to international guidelines, was to verify the analytical performance of nine different types of hematology analyzers (HAs) in the automated platelet analysis.

METHODS

Four hundred eighty-six peripheral blood samples (PB), collected in K₃ EDTA tubes, were analyzed by ABX Pentra, ADVIA2120i, BC-6800, BC-6800 Plus, Cell-DYN Sapphire, DxH800, XE-2100, XE-5000, XN-20 with PLT-F App. Within-run imprecision and between-run imprecision were carried out using PB and material control, respectively. The carryover, low limit of quantification (LoQ), and the PB stability were evaluated.

RESULTS

The carryover was absent for all HAs. The LoQ of PLT ranged between 2.0 (Cell-Dyn Sapphire) and 25.0 × 10⁹ /L (ADVIA 2120i), while immature platelet fraction (IPF) ranged between 1.0 (XN-20) and 12.0 × 10⁹ /L (XE-5000). The imprecision (%CV) increases as the platelet count decreases. No HAs showed desirable CV_APS for PLT counts less than 50.0 × 10⁹ /L, with the exception of Cell-DYN Sapphire (CV 3.0% with PLT-O mean value of 26.7 × 10⁹ /L), XN-20 (CV 2.4% with PLT-F mean value of 21.5 × 10⁹ /L), and BC-6800 Plus (CV 1.9% with PLT-O mean value of 26.5 × 10⁹ /L). The sample stability ranged between under two hours for MPV by ADVIA2120i and 8 hours for other PLT parameters and HAs.

CONCLUSION

The findings of this study may provide useful information regarding carryover, precision, and stability of platelet counts and parameters, especially in thrombocytopenic samples. Moreover, the stability of sample for platelet analysis is conditioned by the HA and by temperature and storage time.

Sorting and magnetic-based isolation of reticulated platelets from peripheral blood

Reticulated Platelets (RPs) are large, RNA-rich, prothrombotic and hyperactive platelets known to be elevated in high-risk populations such as diabetics and patients with acute coronary syndrome. High levels of RPs correlate with mortality and adverse cardiovascular events in patients with coronary artery disease as well as with an insufficient antiplatelet response to thienopyridines and aspirin after percutaneous coronary interventions, making them an appealing drug target. However, processing of platelets is challenging and no specific marker for RPs exists. Until now, the gold standard laboratory-based method to study them is based on the flow cytometric measurement of their cell size and their RNA-content with the fluorescent dye Thiazole Orange (TO). Nevertheless, standardized protocols for staining and processing of RPs are missing and the existing techniques were not applied for cell sorting. We provide here a structured and reproducible method to detect, isolate and collect RPs from peripheral blood by RNA-specific staining with TO implementing several platelet inhibitors as well as magnetic labeling allowing sufficient cell recovery and deep biological investigation of these platelets.

Reticulated platelets – clinical application and future perspectives

Reticulated platelets are immature platelets freshly released from the bone marrow into the circulation and contain vestigial amounts of ribonucleic acid. Thus, they can serve as an indicator for the activity of thrombopoiesis. Despite the current lack of a standardized reference method, two types of hematology analyzers have incorporated a fully automated measurement of reticulated platelets. The “immature platelet fraction” (IPF; Sysmex XE-/XN-series) has some clinical utility in the differential diagnosis of thrombocytopenia. This is less clear for “reticulated platelets” (retPLT; Abbott CELL-DYN Sapphire/Alinity HQ). The usefulness of these parameters in the prediction of platelet recovery after chemotherapy or stem cell transplantation and as a decision aid for platelet transfusions has not been unequivocally confirmed. Recent findings have shown an association of reticulated platelets with an adverse risk in patients with coronary artery disease and stroke as well as resistance to anti-platelet therapy. Furthermore, a role of reticulated platelets for the prediction of sepsis was indicated. However, validation in larger prospective trials is necessary to establish the clinical benefit of reticulated platelets in these conditions. This review gives an overview of the available analytical methods and summarizes the current knowledge regarding the clinical application of reticulated platelets.

Impact of active smoking on the immature platelet fraction and its relationship with the extent of coronary artery disease

INTRODUCTION

Smoking represents a major cardiovascular risk factor, due to the induction of oxidative stress and low-grade, continuous, inflammation that contribute to promote atherothrombosis. However, the mechanisms leading to increased platelet aggregability associated with smoking are only partially defined. A potential role has been hypothesized for immature platelets, a younger and potentially more reactive fraction, previously associated with the main determinants of coronary artery disease (CAD). Therefore, the aim of our study was to define the impact of smoking on the immature platelet fraction (IPF) and its relationship with prevalence and extent of coronary artery disease.

METHODS

We enrolled a cohort of consecutive patients undergoing coronary angiography in a single centre. Significant CAD was defined as at least 1 vessel stenosis >50%, while severe CAD was defined as left main and/or three-vessel disease. IPF was measured at admission by routine blood cell count (Sysmex XE-2100).

RESULTS

We included in our study 2553 patients who were divided according to smoking status (active smokers: 512; nonactive smokers: 2041). Smokers were younger, more frequent males, with lower rate of diabetes mellitus, previous PCI and previous CABG (P < .001, respectively) and were in treatment less often with ARB, BB, nitrates, statins, ASA, clopidogrel, CCB and diuretics (P < .001, respectively) as compared to nonactive smokers. Higher percentage of smokers was observed in patients with higher IPF values, and at multivariate analysis, active smoking resulted as an independent predictor of higher IPF (adjusted OR [95% CI] = 1.59[1.03-2.45], P = .035). Among smokers, higher IPF was associated with lower ejection fraction (P = .034), percentage of acute coronary syndrome (P = .002) and platelet count (P < .001) compared to ones with lower IPF. However, the IPF (according to quartiles values) was not associated with the prevalence and extent of CAD (82.5%, 80.4%, 86.1% and 80.9%, from 1st to 4th quartile, respectively, adjusted OR[95% CI] = 0.98[0.79-1.23], P = .89) and severe CAD (31%, 31.1%, 39.1% and 35.2%, from 1st to 4th quartile, respectively, adjusted OR[95% CI] = 1.03[0.86-1.23], P = .76).

CONCLUSION

The present study shows an independent association between active smoking and the levels of immature platelet fraction in patients undergoing coronary angiography. However, among active smokers, IPF did not result as an independent predictor of CAD or severe CAD.

Impact of aging on immature platelet count and its relationship with coronary artery disease

Despite the fact that elderly patients represent a prevalent and challenging population in the current practice, few data exist on the impact of platelet parameters on cardiovascular risk in these patients. Therefore, the aim of the present study was to evaluate the impact of age on the immature platelet count (IPC) and their relationship with CAD. We included a total of 2236 consecutive patients undergoing coronary angiography in a single center. Elderly patients (age ≥ 75 years) were 756 (33.7%). IPC was measured at admission. Elderly patients were more often females (p < .001), with lower BMI and prevalence of smokers (p < .001), and a more complex cardiovascular risk profile and coronary disease (p = .02). Platelet count decreased with aging (p = .05), whereas no difference in the mean IPC was found between patients < or ≥75 years. In fact, advanced age did not emerge as an independent predictor of IPC above III tertile (≥8.6*10^6/ml), (adjusted OR[95%CI] = 0.97[0.78-1.21], p = .79). When considering elderly patients according to tertiles values of IPC (<5.1,5.1-8.59; ≥8.6*10^6/ml), we found no impact of IPC on the prevalence of CAD (81.1% vs 84.5% vs 81.5%, p = .92; adjusted OR[95%CI] = 1.08[0.67-1.72], p = .75) and its extent (37.7% vs 34.5% vs 40.2%, p = .57; adjusted OR[95%CI] = 1.22[0.85-1.73], p = .28). However, we observed a higher rate of calcified and type C lesions in elderly patients with higher IPC (p = .03 and p < .001, respectively). Therefore, advanced age is not associated with higher immature platelet count and the prevalence and severity of CAD. Moreover, IPC does not contribute to explain the higher prevalence and extent of coronary artery disease observed in elderly patients.

Impact of platelet turnover on long-term adverse cardiovascular outcomes in patients undergoing percutaneous coronary intervention

BACKGROUND

Increased platelet turnover and high platelet reactivity are associated with short-term major adverse cardiovascular events (MACE) after percutaneous coronary intervention (PCI) for acute coronary syndrome (ACS) or stable coronary artery disease (SCAD). We investigated the impact of platelet turnover on long-term MACE.

METHODS

Consecutive patients presenting with ACS or SCAD undergoing PCI between 2009 and 2010 were included. All patients received clopidogrel and aspirin as dual antithrombotic therapy regimen. Multivariable Cox proportional hazard models were applied to assess the prognostic impact of platelet turnover (reticulated platelet count [RPC], mean platelet volume [MPV]) and function on long-term MACE, a composite of cardiovascular death, nonfatal myocardial infarction and nonfatal stroke.

RESULTS

In total, 477 patients were eligible. Mean age was 64.3 ± 12.7 years, 68.8% were male. Median follow-up was 5.8 (IQR 4.2-6.5) years. Median RPC was 7.6 (IQR 5.6-10.4) g/L and median MPV was 10.7 (IQR 10.1-11.3) fL. In univariable analysis, RPC was associated with MACE, both as continuous (HR 1.064 [95%CI 1.021-1.111]; P = .006) and dichotomized (HR 1.693 [95%CI 1.156-2.481]; P = .006) variable. After adjustment, continuous RPC (HR 1.055 [95%CI 1.012-1.099]; P = .010) and dichotomized RPC (HR 1.716 [95%CI 1.152-2.559]; P = .007) remained significantly associated with MACE. Neither MPV nor platelet function testing was associated with long-term adverse outcome.

CONCLUSION

Increased platelet turnover is associated with long-term adverse outcome in patients with coronary artery disease undergoing PCI. Platelet turnover represents a new marker of atherothrombotic risk and might help to guide composition or duration of antiplatelet therapy.

Characterization of surface antigens of reticulated immature platelets

Reticulated platelets (RPs) are immature platelets with high dense granules content and a residual amount of megakaryocyte-derived of mRNA. Increased level of RPs has been found to be an independent predictor of cardiovascular ischemic events, and has been associated with impaired response to various anti-platelet drugs. The study aimed to characterize and compare the surface antigenic properties of reticulated versus mature platelets. Platelets from healthy individuals and diabetic patients were tested at rest and after activation with adenosine diphosphate (ADP). For each patient, we calculated the proportion of RPs and mature platelets using flow cytometry analysis with thiazole orange staining (for RPs) and CD42b platelet-specific antibody. We also tested the surface expression of P-selectin and Annexin V, by double staining flow cytometry in RPs versus mature platelets. A total of 20 subjects were recruited (10 healthy individuals, 10 diabetics). Activation with ADP did not cause a significant change in the proportion of RPs. Following activation, RPs demonstrated a significant increase in the expression of both P-selectin and Annexin V, while mature platelets exhibited a non-significant increase in both markers. These findings were consistent in both healthy subjects and patients with diabetes. In conclusion, RPs have a significantly higher capacity to increase the expression of platelet activation markers compared with mature platelets.

It's reticulated: the liver at the heart of atherosclerosis

Platelets play a critical role in both the initiation and progression of atherosclerosis, and even more so in the ensuing atherothrombotic complications. Low-dose aspirin remains the mainstay of antiplatelet therapy in high-risk patients by reducing the risk of myocardial ischemia, stroke or death due to cardiovascular disease. However, antiplatelet therapies lose their efficacy in people with diabetes mellitus, increasing the risk of future atherothrombotic events. The molecular mechanisms that promote platelet hyperactivity remain unclear but could be due to glycation-induced conformational changes of platelet membranes resulting in impaired aspirin entry or less-efficient acetylation/compensatory increase in COX-2 expression in newborn platelets. Emerging evidence from our laboratory and elsewhere suggest that enhanced platelet turnover (thrombopoiesis), particularly the production of immature reticulated platelets from the bone marrow, could contribute to atherosclerotic complications. We have identified a major role for neutrophil-derived S100A8/A9, a damage-associated molecular pattern, in driving reticulated thrombopoiesis by directly interacting with its receptors on Kupffer cells in the liver. In this review, we discuss the role of hepatic inflammation in driving reticulated platelet production and suggest potential targets to control their production, improve efficacy of current antiplatelet therapies and reduce the risk of atherothrombotic complications.

Antiplatelet Agents for the Treatment and Prevention of Coronary Atherothrombosis

Antiplatelet drugs provide first-line antithrombotic therapy for the management of acute ischemic syndromes (both coronary and cerebrovascular) and for the prevention of their recurrence. Their role in the primary prevention of atherothrombosis remains controversial because of the uncertain balance of the potential benefits and risks when combined with other preventive strategies. The aim of this consensus document is to review the evidence for the efficacy and safety of antiplatelet drugs, and to provide practicing cardiologists with an updated instrument to guide their choice of the most appropriate antiplatelet strategy for the individual patient presenting with different clinical manifestations of coronary atherothrombosis, in light of comorbidities and/or interventional procedures.

Platelet indices and glucose control in type 1 and type 2 diabetes mellitus: A case-control study

BACKGROUND AND AIMS

The relationship between platelet indices and glucose control may differ in type 1 (T1DM) and type 2 (T2DM) diabetes. We aimed to investigate differences in mean platelet volume (MPV), platelet count, and platelet mass between patients with T1DM, T2DM, and healthy controls and to explore associations between these platelet indices and glucose control.

METHODS AND RESULTS

A total of 691 T1DM and 459 T2DM patients and 943 control subjects (blood donors) were included. HbA1c was measured in all subjects with diabetes and 36 T1DM patients further underwent 24 h-continuous glucose monitoring to estimate short-term glucose control (glucose mean and standard deviation). Adjusting for age and sex, platelet count was higher and MPV lower in both T1DM and T2DM patients vs control subjects, while platelet mass (MPV × platelet count) resulted higher only in T2DM. Upon further adjustment for HbA1c, differences in platelet count and mass were respectively 19.5 × 10⁹/L (95%CI: 9.8-29.3; p < 0.001) and 101 fL/nL (12-191; p = 0.027) comparing T2DM vs T1DM patients. MPV and platelet count were significantly and differently related in T2DM patients vs both T1DM and control subjects; this difference was maintained also accounting for HbA1c, age, and sex. Platelet mass and the volume-count relationship were significantly related to HbA1c only in T1DM patients. No associations were found between platelet indices and short-term glucose control.

CONCLUSION

By accounting for confounders and glucose control, our data evidenced higher platelet mass and different volume-count kinetics in subjects with T2DM vs T1DM. Long-term glucose control seemed to influence platelet mass and the volume-count relationship only in T1DM subjects. These findings suggest different mechanisms behind platelet formation in T1DM and T2DM patients with long-term glycaemic control being more relevant in T1DM than T2DM.

Distinct characteristics of neonatal platelet reactivity

Platelets undergo a process of developmental maturation, and hence its regulation of vascular integrity and control of hemostasis at various stages of neonatal ages deserves better characterization. Functional assays for platelets require a larger volume of blood than what is feasible to collect in neonates, creating a technical hurdle that has been a challenge to investigate neonatal platelets. For this reason, the current knowledge of neonatal platelet function has been based on studies from cord blood-derived platelets as a surrogate for neonatal peripheral blood. Studies indicate that neonatal platelets are hypofunctional to various agonists, although neonates tend to maintain normal hemostasis. This apparently paradoxical finding may be due to several factors, such as elevated functionally potent von Willebrand factor multimers or hematocrit levels, in the neonatal blood that enhance the platelet and vessel wall interaction, and counteract platelet hyporeactivity. This review describes the functional characteristics of neonatal platelets, differences in platelet reactivity between neonates and adults, and potential biomarkers of platelet activation.

Neutrophil-derived S100 calcium-binding proteins A8/A9 promote reticulated thrombocytosis and atherogenesis in diabetes

Platelets play a critical role in atherogenesis and thrombosis-mediated myocardial ischemia, processes that are accelerated in diabetes. Whether hyperglycemia promotes platelet production and whether enhanced platelet production contributes to enhanced atherothrombosis remains unknown. Here we found that in response to hyperglycemia, neutrophil-derived S100 calcium-binding proteins A8/A9 (S100A8/A9) interact with the receptor for advanced glycation end products (RAGE) on hepatic Kupffer cells, resulting in increased production of IL-6, a pleiotropic cytokine that is implicated in inflammatory thrombocytosis. IL-6 acts on hepatocytes to enhance the production of thrombopoietin, which in turn interacts with its cognate receptor c-MPL on megakaryocytes and bone marrow progenitor cells to promote their expansion and proliferation, resulting in reticulated thrombocytosis. Lowering blood glucose using a sodium-glucose cotransporter 2 inhibitor (dapagliflozin), depleting neutrophils or Kupffer cells, or inhibiting S100A8/A9 binding to RAGE (using paquinimod), all reduced diabetes-induced thrombocytosis. Inhibiting S100A8/A9 also decreased atherogenesis in diabetic mice. Finally, we found that patients with type 2 diabetes have reticulated thrombocytosis that correlates with glycated hemoglobin as well as increased plasma S100A8/A9 levels. These studies provide insights into the mechanisms that regulate platelet production and may aid in the development of strategies to improve on current antiplatelet therapies and to reduce cardiovascular disease risk in diabetes.

Novel Risk Markers and Risk Assessments for Cardiovascular Disease

The use of risk markers has transformed cardiovascular medicine, exemplified by the routine assessment of troponin, for both diagnosis and assessment of prognosis in patients with chest pain. Clinical risk factors form the basis for risk assessment of cardiovascular disease and the addition of biochemical, cellular, and imaging parameters offers further refinement. Identifying novel risk factors may allow greater risk stratification and a steady, but gradual progression toward precision medicine. Indeed, the generation of data in this area of research is explosive and when combined with new technologies and techniques provides the potential for more refined, targeted approaches to cardiovascular medicine. Although discussing the most recent developments in this field, this review article aims to strike a balance between novelty and validity by focusing on recent large sample-size studies that have been validated in a separate cohort in most cases. Risk markers related to atherosclerosis, thrombosis, inflammation, cardiac injury, and fibrosis are introduced in the context of their pathophysiology. Rapidly developing new areas, such as assessment of micro-RNA, are also explored. Subsequently the prognostic ability of these risk markers in coronary artery disease, heart failure, and atrial fibrillation is discussed in detail.

Platelet turnover predicts outcome after coronary intervention

Elevated platelet turnover contributes to high platelet reactivity. High platelet reactivity after percutaneous coronary intervention (PCI) is associated with major adverse cardiovascular events (MACE). The purpose of this study was to determine the prognostic value of platelet turnover and function with regard to MACE after PCI with stent implantation. In this prospective observational study, 486 consecutive patients after PCI on aspirin and clopidogrel were included to determine platelet turnover (mean platelet volume (MPV), reticulated platelet fraction (RPF)) and platelet function (multiple electrode aggregometry (MEA), vasodilator-stimulated phosphoprotein-phosphorylation (VASP-P) assay). At six-months follow-up, MACE occurred in 10.7 % of patients. RPF (odds ratio [OR]=1.173 (95% confidence interval [CI 95 %] 1.040-1.324), p=0.009) and MPV (OR=1.459 (CI 95 % 1.059-2.008), p=0.021) were univariable predictors of MACE, whereas VASP-P (OR=1.016 (CI 95 % 1.000-1.032), p=0.052) and MEA (OR=0.999 (CI 95 % 0.980-1.017), p=0.895) failed to predict MACE. RPF remained the only platelet variable independently associated with MACE. The best model to predict MACE included: troponin I (OR=1.007 (CI 95 % 1.002-1.012), p=0.009), RPF (OR=1.136 (CI 95 % 1.001-1.288), p=0.048), CRP (OR=1.008 (CI 95 % 1.001-1.014), p=0.023) and history of myocardial infarction (OR=2.039 (CI 95 % 1.093-3.806), p=0.025). RPF (OR=1.211 (CI 95 % 1.042-1.406), p=0.012) was also independently associated with in-hospital bleedings. In conclusion, RPF as index of platelet turnover is an independent predictor of MACE and bleeding events in PCI patients on dual antiplatelet therapy. Since RPF can reliably be quantified along with routine haemograms, RPF might easily be applied in the setting of cardiovascular risk prediction.

Usefulness of Mean Platelet Volume to Predict Significant Coronary Artery Disease in Patients With Non-ST-Elevation Acute Coronary Syndromes

Acute coronary syndrome (ACS) is characterized by unstable plaque with thrombotic process involving central role of platelets. The diagnosis and prediction of significant coronary artery disease (CAD) in non-ST-elevation ACS (NSTE-ACS) can be challenging. The central role of platelets in acute atherothrombosis in NSTE-ACS spurred appreciable interest in the diagnostic and predictive role of platelet activity. Mean platelet volume (MPV) is one of the most promising laboratory markers in patients with CAD. This retrospective study was designed to investigate the diagnostic and predictive value of high MPV levels in patients with NSTE-ACS with significant CAD. A total of 213 patients (men 53%, mean age 61 ± 12.3 years) with NSTE-ACS were enrolled from 2011 to 2016 from 2 teaching hospitals. Patients' demographic, laboratory, and angiographic data were collected. Significant CAD was defined as ≥70% stenosis in at least 1 major coronary artery. Patients with high MPV (MPV ≥9 fl) had more significant CAD (55% vs 35%, p = 0.005), lower platelet count (204 ± 59 × 1,000/μl vs 246 ± 56 × 1,000/μl, p = 0.001), and higher HbA1c (6.9 vs 6.4, p = 0.02). Patients with significant CAD had higher MPV level (9.2 ± 1.07 vs 8.6 ± 1.03 fl, p = 0.001), higher MPV/platelet ratio (0.46 vs 0.40, p = 0.01), older age (64.5 ± 11 vs 59.2 ± 12 years, p = 0.02), and lower high-density lipoprotein level (42 ± 12 vs 47 ± 16, p = 0.01). Multivariate analysis showed that increased age, high MPV, high troponin, and low high-density lipoprotein levels were associated with significant CAD. Patients with high MPV along with high troponin level demonstrated a 4.8-fold increased risk for significant CAD compared to those with normal MPV and high troponin (odds ratio 4.8, 95% confidence interval 1.31 to 17.6, p = 0.001). In conclusion, considering high MPV in the context of elevated troponin level increases the predictive value of screening for significant CAD, and this result may help determine who is most likely to benefit from cardiac catheterization.

Platelet index levels and cardiovascular mortality in incident peritoneal dialysis patients: a cohort study

Prior studies have shown that the levels of some platelet (PLT) indices were associated with mortality in patients undergoing hemodialysis. We aimed to investigate whether the changes in PLT indices associated with mortality in patients on peritoneal dialysis (PD). A single-center, retrospective observational cohort study was conducted in incident PD patients from 1 January 2006 to 31 December 2012, and followed up until 31 December 2014. Cox proportional hazard models were used to examine the relationships between the levels of PLT indices including PLT, plateletcrit (PCT), mean platelet volume (MPV), platelet distribution width (PDW), platelet large cell ratio (PLCR), and mortality. Of 1324 patients, 276 (20.8%) died during follow-up (median, 37; IQR, 3-107.4 months), among which 134 were due to cardiovascular diseases (CVD). The highest tertile of PLT levels at baseline was associated with increased risk for cardiovascular mortality after adjustment for demographic, clinical characteristics, and laboratory variables (hazard ratio [HR]:1.93; 95% confidence interval [CI]: 1.16-3.20). The similar treads were also observed in the middle and the highest tertile of the PCT level (HR: 1.68, 95%CI: 1.00-2.81 and HR: 1.89, 95%CI: 1.14-3.14, respectively). In addition, the highest tertile of PCT was associated with increased all-cause mortality (HR: 1.41, 95%CI: 1.01-1.96). However, none of the associations in MPV, PDW, and PLCR analyses reached statistical significance (HR: 0.71, 95%CI: 0.43-1.16; HR: 0.72, 95%CI: 0.45-1.18 and HR: 0.74, 95%CI: 0.46-1.19, respectively). These results suggest that higher PLT and PCT may be associated with higher risk for cardiovascular mortality in incident PD patients. Additional studies are needed to investigate whether correction of these two PLT indices reduces the risk.