Do immature platelet levels in chest pain patients presenting to the emergency department aid in the diagnosis of acute coronary syndrome?

Immature Platelet Fraction and Acute Coronary Syndrome; a Systematic Review and Meta-Analysis

Introduction

Immature Platelet Fraction (IPF) is a measure of the proportion of reticulated platelets (RPs) to all platelets in circulation. IPF may have both prognostic and diagnostic values in patients with Acute Coronary Syndrome (ACS). This study aims to comprehensively summarize the diagnostic utility of IPF levels in patients with ACS, specifically focusing on its ability to differentiate between different subtypes of ACS.

Methods

We conducted a systematic search in online databases including MEDLINE, Scopus, and Google Scholar up to March 4th 2024, to identify relevant studies. The random-effect model, employing inverse variance for mean differences (MD) and Mantel-Haenszel methods for odds ratios (OR) were utilized to combine the data. Joanna Briggs Institute (JBI) appraisal tool was employed to assess the quality of included studies.

Results

Our systematic review contains 15 articles with a total sample size of 2,030 ACS patients. Pooled analysis revealed significant differences in IPF levels of ACS patients compared to healthy controls (MD (95%CI): 2.85 (0.86, 4.85), P-value = 0.004) and stable angina patients (MD (95%CI): 0.58 (0.23, 0.92), P-value < 0.001). Subgroup comparisons within ACS patients demonstrated higher IPF levels in myocardial infarction (MI) vs. unstable angina (UA) (MD (95%CI): 1.81 (0.41, 3.22), P-value = 0.01), ST elevation MI (STEMI) vs. non-ST elevation (NSTEMI) ACS (MD (95%CI): 0.74 (0.31, 1.17), P-value < 0.001), and NSTEMI vs. UA (MD (95% CI): 1.07 (0.24, 1.90), P-value = 0.01).

Conclusion

IPF levels could increase in patients with ACS, particularly during the acute phase of STEMI. This suggests that IPF may be a useful biomarker for early diagnosis of ACS. Additionally, IPF levels may help differentiate between ACS subtypes.

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.

Platelets and the Atherosclerotic Process: An Overview of New Markers of Platelet Activation and Reactivity, and Their Implications in Primary and Secondary Prevention

The key role played by platelets in the atherosclerosis physiopathology, especially in the acute setting, is ascertained: they are the main actors during thrombus formation and, thus, one of the major investigated elements related to atherothrombotic process involving coronary arteries. Platelets have been studied from different points of view, according with the technology advances and the improvement in the hemostasis knowledge achieved in the last years. Morphology and reactivity constitute the first aspects investigated related to platelets with a significant body of evidence published linking a number of their values and markers to coronary artery disease and cardiovascular events. Recently, the impact of genetics on platelet activation has been explored with promising findings as additional instrument for patient risk stratification; however, this deserves further confirmations. Moreover, the interplay between immune system and platelets has been partially elucidated in the last years, providing intriguing elements that will be basic components for future research to better understand platelet regulation and improve cardiovascular outcome of patients.

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.

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.

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: a review of the available evidence

Immature platelets or reticulated platelets are newly released thrombocytes. They can be identified by their large size and high RNA cytoplasm concentration. Immature platelet fraction (IPF) represents the percentage of immature circulative platelets to the total number of platelets. The development of analytical standardization of this hematological parameter by new automated devices allowed a better exploration of its contribution in a context of thrombocytopenia. In fact, several studies had confirmed its clinical utility to differentiate immune thrombocytopenia from other causes of thrombocytopenia. IPF can also predict platelets recovery after chemotherapy and successful engraftment. In addition, immature platelets have shown utility in other diseases such as coronary artery diseases, bacterial infections and liver diseases. Despite all these advantages, immature platelet fraction can be increased in some cases of thrombocytopenia characterized by platelets hypoproduction. The aim of this review is to present the immature platelet fraction contribution in clinical practice.

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.

Is Migraine an MPV-Related Disease? An Observational Study of Polish Neurological Patients

Many studies have found correlations between abnormal MPV and clinical reactivity in a variety of diseases. In the present paper, we sought MPV-related neurological diseases that are less frequently reported in the literature. The electronic medical records of 852 neurological patients with mean platelet volume (MPV) measurements (F = 45%, age = 55.7 ± 18.7, 8–104) were searched after the patients had received a diagnosis of a neurological disease (new and old episodes) according to the nine classes of the International Statistical Classification of Diseases and Related Health Problems, 10th revision (ICD-10). A set of consecutive statistical methods (i.e., cluster analysis, segmented regression, linear correlation, propensity score matching, and mixed effects Poisson regression) were used to establish a link between MPV and neurological disease. A statistically significant (p < 0.05) relationship with MPV was found only in pain syndrome patients, with seven out of eight clinically diagnosed migraine episodes. With all other ICD-10 classes of neurological diseases, the effect of MPV was found to be nonsignificant (p > 0.05). MPV may implicate a clinical relationship with pain syndrome and migraine episodes. More complex statistics could help analyse data and find new correlations.

Prognostic significance of reticulated platelet levels in diabetic patients with stable coronary artery disease

Levels of reticulated platelets (RP) increase during high platelet turnover conditions, and have been shown to correlate with diabetes mellitus (DM) status. Little is known regarding the prognostic significance of levels of RP among patients with stable coronary artery disease (SCAD). The study consisted of patients with SCAD and DM, who visited our cardiology outpatient clinic between June 2016 and February 2017. RP levels were measured at baseline as immature platelet fraction (IPF)%, using flow cytometry. Outcomes at 2 years consisted of bleeding events and major adverse cardiovascular events (MACE), which included death, myocardial infarction, cerebrovascular accident and urgent revascularization. The study included 104 patients (mean age - 71.2 ± 9.5 years, 76.9% were male, and 83.7% had hypertension). IPF was significantly higher at baseline among patients who had suffered from a MACE (4.57% vs. 2.53%, p < .001), and lower in patients who had suffered from bleeding events, compared with those who had not (1.57% vs. 3.00%, p = .004). There were higher rates of MACE at higher IPF quartiles (p < .001, AUC-0.770), and higher rates of bleeding at the lowest quartiles (p = .007, AUC-0.781). In SCAD patients with DM, levels of RP are associated with a higher risk of MACE, and inversely correlated with the risk of bleeding.

Atherosclerosis, myocardial infarction and primary hemostasis: Impact of platelets, von Willebrand factor and soluble glycoprotein VI

INTRODUCTION

Little is known about peril constellations in primary hemostasis contributing to an acute myocardial infarction (MI) in patients with already manifest atherosclerosis. The study aimed to establish a predicting model based on six biomarkers of primary hemostasis: platelet count, mean platelet volume, hematocrit, soluble glycoprotein VI, fibrinogen and von Willebrand factor ratio.

MATERIALS AND METHODS

The biomarkers were measured in 1.491 patients with manifest atherosclerosis of the Leipzig (LIFE) heart study. Three groups were divided: patients with coronary artery disease (900 patients) and patients with atherosclerosis and either ST-elevated MI (404 patients) or Non-ST-elevated MI (187 patients). Correlations were analyzed by non-linear analysis with Self Organizing Maps. Classification and discriminant analysis was performed using Learning Vector Quantization.

RESULTS AND CONCLUSIONS

The combination of hemostatic biomarkers is regarded as valuable tool for identifying patients with atherosclerosis at risk for MI. Nevertheless, our study contradicts this belief. The biomarkers did not allow to establish a predicting model usable in daily patient care. Good specificity and sensitivity for the detection of MI was only reached in models including acute phase parameters (specificity 0,9036, sensitivity 0,7937 in men; 0,8977 and 0,8133 in women). In detail, hematocrit and soluble glycoprotein VI were significantly different between the groups. Significant dissimilarities were also found for fibrinogen (in men) and von Willebrand factor ratio. In contrast, the most promising parameters mean platelet volume and platelet count showed no difference, which is an important contribution to the controversy concerning them as new risk and therapy targets for MI.

Clinical utility of mean platelet volume and immature platelet fraction in acute coronary syndrome

Background

Platelets play an important role in the pathogenesis of acute coronary syndrome (ACS). Patients with ACS have an increased mean platelet volume (MPV) and immature platelet fraction (IPF) resulting in elevation of thrombotic ability. In this study, we evaluated the diagnostic performance of MPV and IPF in identifying suspected ACS patients at emergency department. Moreover, we investigated the correlation between MPV or IPF with initial troponin I (TnI), one of the current ACS biomarkers.

Methods

This was a single-center study recruiting suspected ACS patients who had acute chest pain at the emergency department. Whole blood samples were obtained from all participants and MPV and IPF were measured by Sysmex XE-5000 hematology analyzer within 20 min of blood sampling. The diagnostic values of MPV and IPF in identifying ACS were analyzed retrospectively.

Result

In this study, 63 in 104 suspected ACS patients were diagnosed as ACS (65.3%). MPV and IPF were higher in ACS patients compared to non-ACS patients (MPV: 10.7 ± 0.80 fL vs 10.0 ± 0.64 fL, p < 0.001; IPF: 3.7 ± 2.64% vs 3.1 ± 2.69%, p = 0.030). MPV and IPF were similar in unstable angina and acute myocardial infarction patients. We showed that elevation of MPV could be an independent predictive factor of ACS (odds ratio: 5.038). At the optimal cut-off value of 10.55 fL (AUC 95% CI: 0.637–0.836), the diagnostic performance of MPV in predicting ACS had an area under a receiver operating characteristic curve (AUC) of 0.736 with sensitivity and specificity of 54.2% and 82.8%, respectively. Patients with both of initial TnI and MPV higher than the established cut-off value had increased incidence (3.792 fold) for ACS development compared to patients with TnI below the cut-off value. Furthermore, diagnosing ACS with both MPV and initial TnI increased the positive predictive value from 84.2% to 86.7%. No correlation was observed between MPV or IPF and the mortality rate of ACS patients (MPV: 3.8% vs 11.1%, p = 0.300; IPF: 12.0% vs 37.5%, p = 0.054).

Conclusion

Here we show that ACS patients have higher MPV and IPF compared to non-ACS patients. We further demonstrate that MPV can be utilized as an independent predictor for early diagnosis of low-risk ACS patients who have acute chest pain.

Reference intervals for absolute and percentage immature platelet fraction using the Sysmex XN-10 automated haematology analyser in a UK population

BACKGROUND

Immature platelet fraction (IPF) estimation is a non-invasive and sensitive test that is available on recently introduced Sysmex XN-series of automated haematology analysers. It is a direct cellular indicator of thrombopoiesis. The aim of this study was to establish reference intervals for IPF, for both absolute (A-IPF) and percentage (%-IPF) measurements.

MATERIAL AND METHODS

A total of 2366 samples that met the inclusion criteria were assayed for full blood count on the Sysmex XN-10 and a non-parametric percentile method was used for calculating the reference intervals.

RESULTS

After the outliers were excluded, the reference interval for %-IPF and A-IPF on Sysmex XN-10 were 1.6-10.1% and 4.37-23.21 × 10⁹/L in total individuals, respectively. There was a statistical significance noted between the sexes (p = .004) for %-IPF, therefore a sex-specific reference interval was established, which was 1.8-10.0% for the males and 1.5-10.1% for females. No significant difference in sex status for A-IPF and age status for both %-IPF and A-IPF was observed. A very poor correlation was estimated between age versus %-IPF, ρ = 0.0156, and age versus A-IPF, ρ = -0.0023, indicating that there is no overall biological relationship between age and these parameters. As expected, a strong correlation between %-IPF and A-IPF was noted which could be attributed to their inter-relatedness.

CONCLUSIONS

This large-scale study showed comparable reference intervals with the previous studies for %-IPF and A-IPF in a UK population. It found the need to establish sex-specific reference intervals for %-IPF, but not for A-IPF, whereas reference intervals were found to be stable across the age range.

Antiplatelet drugs in patients with enhanced platelet turnover: biomarkers versus platelet function testing

Platelets are key players in atherothrombosis. Antiplatelet therapy comprising aspirin alone or with P2Y12-inhibitors are effective for prevention of atherothrombotic complications. However, there is interindividual variability in the response to antiplatelet drugs, leaving some patients at increased risk of recurrent atherothrombotic events. Several risk factors associated with high on-treatment platelet reactivity (HTPR), including elevated platelet turnover, have been identified. Platelet turnover is adequately estimated from the fraction of reticulated platelets. Reticulated platelets are young platelets, characterised by residual messenger RNA. They are larger, haemostatically more active and there is evidence that platelet turnover is a causal and prognostic factor in atherothrombotic disease. Whether platelet turnover per se represents a key factor in pathogenesis, progression and prognosis of atherothrombotic diseases (with focus on acute coronary syndromes) or whether it merely facilitates insufficient platelet inhibition will be discussed in this state-of-the art review.