Measurement of reticulated platelets by simple flow cytometry: An indirect thrombocytopoietic marker

Immature Platelet Fraction and Clinical Outcomes in Patients Undergoing Transcatheter Aortic Valve Implantation

INTRODUCTION

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 relative to the total number of platelets. The role of IPF in patients undergoing transcatheter aortic valve implantation (TAVI) is unknown. The aim of the current trial was to assess the levels of IPF in patients undergoing TAVI and correlation with clinical outcomes.

MATERIAL AND METHODS

Immature platelet fraction levels were measured 3 times in all patients (preprocedure, 1-2 days post-procedure and 1-month post-procedure). Immature platelet fraction measurement was carried out using an autoanalyzer (Sysmex XE-2100). Patients were followed for 12 months. Primary outcomes were defined as complications during hospitalizations, rehospitalization, and mortality.

RESULTS

Fifty-one patients were included in the study. Mean age was 79.8 (±9.6), and 28 (55%) were women. Twenty-one patients (41%) had complications: Of them, 6 of 21 (29%) occurred during hospitalizations (2-vascular complications; 2-sepsis, 2-implantation of a pacemaker), 9 of 21 (43%) patients were rehospitalized after the index admission, and 6 patients died during the follow-up period. Multivariate Cox regression analysis found that IPF < 7% in at least one of the 3 tests was associated with worse outcomes (hazard ratio 3.42; 95% CI 1.11-10.5, P = .032).

CONCLUSION

Immature platelet fraction >7% in patients undergoing TAVI is associated with worse outcomes. Further studies are needed to better understand this phenomenon.

Laboratory Markers of Platelet Production and Turnover

Platelets are formed from bone marrow megakaryocytes, circulate in blood for 7-10 days, and then are destroyed in the spleen and/or liver. Platelet production depends on the megakaryocyte population state in the bone marrow: number and size of the cells. The platelet turnover, i.e., the number of platelets passing through the bloodstream in a certain time, is determined by both the rate of their production and the rate of their destruction. The review considers laboratory markers, which are used to assess platelet production and turnover in the patients with hematologic and cardiovascular pathologies. These markers include some characteristics of platelets themselves: (i) content of reticulated ("young") forms in the blood detected by their staining with RNA dyes; (ii) indicators of the platelet size determined in hematology analyzers (mean volume, percentage of large forms) and in flow cytometers (light scattering level). Alterations of platelet production and turnover lead to the changes in blood plasma concentrations of such molecules as thrombopoietin (TPO, main mediator of megakaryocyte maturation and platelet formation in the bone marrow) and glycocalicin (soluble fragment of the membrane glycoprotein Ib detached from the surface of platelets during their destruction). Specific changes in the markers of platelet production and turnover have been observed in: (i) hypoproductive thrombocytopenias caused by suppression of megakaryocytes in the bone marrow; (ii) immune thrombocytopenias caused by accelerated clearance of the autoantibody-sensitized platelets; and (iii) thrombocytosis (both primary and reactive). The paper presents the data indicating that in patients with cardiovascular diseases an increased platelet turnover and changes in the corresponding markers (platelet size indexes and content of reticulated forms) are associated with the decreased efficacy of antiplatelet drugs and increased risk of thrombotic events, myocardial infarction, and unstable angina (acute coronary syndrome).

Primary immune thrombocytopenia: a 'diagnosis of exclusion'?

Current diagnosis of primary immune thrombocytopenia (ITP) is presumptive, centered on excluding other causes of thrombocytopenia. The diagnosis of ITP is challenging because of the wide range of potential inherited and acquired causes of thrombocytopenia. The treatment of ITP is empiric with steroids, high-dose immunoglobulin, immunosuppressants and thrombopoietin agonists with potential side effects. We searched Medline and Cochrane databases, reviewed the study data and analyzed the individual diagnostic tests for their evidence-based role in the diagnosis of ITP. We then analyzed the strength of the scientific evidence for each diagnostic test in the diagnosis of ITP and identified gaps in the diagnostic accuracy. The diagnostic challenges in ITP include: insufficient evidence for the individual test for diagnosis of ITP, no standardized protocol/guideline for diagnosis, hurdles in accessing the available resources and failure to correlate the clinical data while reviewing the blood smear. We did not identify a diagnostic test that clinicians can use to confirm the diagnosis of ITP. In the absence of a diagnostic test of proven value in ITP, the clinician is best served by a comprehensive history and physical examination, complete blood count and review of the peripheral blood smear in evaluating thrombocytopenia.

Immature platelet fraction over time and clinical outcomes in patients with acute myocardial infarction

BACKGROUND

Immature platelets in the circulation can be measured as immature platelet fraction (IPF). Limited data exist regarding IPF during the course of an acute myocardial infarction (AMI), the association between IPF and extent of cardiac damage, and the long-term prognostic implications of IPF in patients with AMI.

AIMS

To examine the temporal course of IPF during the first month after AMI, the association between IPF and extent of cardiac damage, and the long-term prognostic effect of IPF in AMI patients.

METHODS

Patients with AMI treated with percutaneous coronary intervention (PCI) were examined. IPF was evaluated by a Sysmex XN-3000 autoanalyzer, at 4 time points: baseline; one day post-PCI; 3 days post-PCI, and 30 days post-PCI. The association between peak troponin-T levels and IPF was evaluated. One-year clinical outcomes (cardiac hospitalization, urgent revascularization, or death) were assessed.

RESULTS

One hundred patients were included, mean age was 59.5 ± 11.3 years, 82 were men, 27 had diabetes, and 54 were hospitalized with ST-segment elevation myocardial infarction (STEMI) and 46 with non-ST segment elevation myocardial infarction (NSTEMI). The levels of IPF modestly decreased a day after PCI but did not change in subsequent measurements. Peak troponin-T level was significantly associated with the levels of IPF at all 4 time points. IPF levels three days post-PCI were associated with the composite clinical outcome at 1 year.

CONCLUSIONS

The levels of IPF following AMI remain relatively stable over a one-month period. Higher levels of IPF during the acute phase of AMI appear to be associated with worse cardiac outcomes at 1 year.

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.

The mechanisms of sulfated polysaccharide drug of propylene glycol alginate sodium sulfate (PSS) on bleeding side effect

Propylene glycol alginate sodium sulfate (PSS), a sulfated polysaccharide derivative, has been used as a heparinoid drug to prevent and treat hyperlipidemia and ischemic cardio-cerebrovascular diseases in China for 30 years. But its bleeding risk should not be overlooked. Here we clarified the reasons and mechanism leading to bleeding side effect of PSS. It was found that PSS fractions with low mannuronic acid (M)/guluronic acid (G) ratio and high molecular weight (Mw) can excessively extend activated partial thromboplastin time (APTT) and thrombin time (TT), over-inhibit the thrombin (FIIa) activity mediated by anti-thrombin III (ATIII) to induce bleeding risk. In addition, the fraction of low M/G ratio can suppress platelet aggregation mediated by adenosine diphosphate (ADP) and induce platelet reduction by improving platelet antibody (PA)-IgA/G in serum and by inhibiting or damaging the bone marrow hematopoietic function. And the fraction of high Mw can restrain the reticulated platelet (RP) production, then reduce mean platelet volume (MPV) and platelet-large cell counts or ratio, and finally decrease platelet amount by inhibiting or damaging the bone marrow hematopoietic function. In brief, PSS fractions with low M/G ratio and high Mw were the main reasons to bring about bleeding by excessively suppressing coagulant factors activities and weakening platelet function. Our results suggested that it is very necessary to control the M/G ratio and the range of Mw of PSS to guarantee its safety and effectiveness in clinical.

Reticulated platelets predict cardiovascular death in acute coronary syndrome patients

Reticulated platelets (RP) are newly-formed platelets with a greater mass, a residual amount of RNA and an increased prothrombotic potential. No studies investigating the association between RP and the risk of cardiovascular death in acute coronary syndrome (ACS) patients are available. In the frame of the AMI-Florence 2 study, we investigated RP in 229 (154 M/ 75 F) ACS patients (125 ST-elevation myocardial infarction [STEMI]; 104 Non-STEMI/Unstable Angina). RP were measured by using the Sysmex XE-2100 haematology analyzer and were expressed as the percentage of RP out of the total optical platelet count (immature platelet fraction; IPF) and as the percentage of RP highly fluorescent (H-IPF). At one-year follow-up, 22 out of 229 patients (9.6%) died from cardiovascular causes. Higher values of IPF (p=0.05) and H-IPF (p=0.006) were detected in dead compared to alive patients. A receiver operating characteristics curve analysis identified IPF ≥3.3% and H-IPF ≥0.9% as optimal cut-off values to predict cardiovascular death. At the multivariate model adjusted for the Global Registry of Acute Coronary Events (GRACE) risk score, the association between RP and cardiovascular death remained significant for both IPF [OR (95%CI) : 4.15 (1.24–13.91) p=0.02] and H-IPF [OR (95%CI): H-IPF 5.03 (1.38–18.38) p=0.01]. In conclusion, RP are independent predictors of cardiovascular death and may be useful in improving risk stratification for ACS patients. Future prospective studies to evaluate the role of RP in determining cardiovascular events are warranted.

The Centenary of Immune Thrombocytopenia-Part 2: Revising Diagnostic and Therapeutic Approach

Primary immune thrombocytopenia (ITP) is the most common cause of thrombocytopenia in children and adolescents and can be considered as a paradigmatic model of autoimmune disease. This second part of our review describes the clinical presentation of ITP, the diagnostic approach and overviews the current therapeutic strategies. Interestingly, it suggests an algorithm useful for differential diagnosis, a crucial process to exclude secondary forms of immune thrombocytopenia (IT) and non-immune thrombocytopenia (non-IT), which require a different therapeutic management. Advances in understanding the pathogenesis led to new therapeutic targets, as thrombopoietin receptor agonists, whose role in treatment of ITP will be discussed in this work.

Importance of immature platelet fraction as predictor of immune thrombocytopenic purpura

Background and Objective:

Immune thrombocytopenic purpura (ITP) is a clinical syndrome in which a decreased number of circulating platelets (thrombocytopenia) manifests as a bleeding tendency, easy bruising (purpura) or extravasation of blood from capillaries into skin and mucous membranes (petechiae). The diagnosis of ITP can be made clinically on the basis of symptoms, we need to see if ITP can be confirmed in patients by quantification of residual RNA containing immature platelets (megakaryocytic mass) or immature platelets fraction (IPF) using automated hematology analyzers (Sysmex XE-2100).

Methods:

In order to check the efficacy of IPF% parameter of Sysmex XE-2100 a total of 231 patients of thrombocytopenia were included in this study. Complete blood count (CBC) was estimated. The data was statistically analyzed by SPSS version 17.

Results:

About 62 patients were diagnosed as ITP and 169 patients were diagnosed as non ITP on the basis of clinical history. The mean IPF % value of ITP patients was 16.39% and the IPF % value of Non ITP patients was ~7.69% respectively. There was no significant difference in IPF% values with respect to time between sampling and acquisition of complete blood count. The diagnostic sensitivity of IPF% as biomarker for ITP and non-ITP was 85.71% (95%CI: 84.04% to 85.96%) and 41.76% (95% CI: 39.87% to 43.65%).

Conclusion:

The mean IPF % value by Sysmex XE-2100 can be used to predict ITP.

Immature platelet fraction measured on the Sysmex XN hemocytometer predicts thrombopoietic recovery after autologous stem cell transplantation

Objectives

A period of thrombocytopenia is common after stem cell transplantation (SCT). To prevent serious bleeding complications, prophylactic platelet transfusions are administered. Previous studies have shown that a rise in immature platelets precedes recovery of platelet count. Our aim was to define a cutoff value for immature platelets predicting thrombopoietic recovery within 2 d.

Methods

Hematological parameters were measured on the Sysmex XN hemocytometer. We calculated reference change values (RCV) for platelets in eight healthy individuals as marker for platelet recovery. To define a cutoff value, we performed ROC analysis using data from 16 autologous SCT patients.

Results

RCV for platelet concentration was 14.1%. Platelet recovery was observed 13 (median; range 9–31) days after SCT. Increase in immature platelet fraction (IPF) before platelet recovery was seen in all autologous SCT patients. Optimal cutoff IPF was found to be 5.3% for platelet recovery within 2 d (specificity 0.98, sensitivity 0.47, positive predictive value 0.93).

Conclusions

We identified an optimal cutoff value for IPF 5.3% to predict platelet recovery after autologous SCT within 2 d. Implementing this cutoff value in transfusion strategy may reduce the number of prophylactic platelet transfusions.

New insights into thrombopoiesis in neonatal sepsis

Thrombocytopenia is one of the most frequent hematologic abnormalities in the neonatal period, affecting about 18-35% of all patients admitted to the Neonatal Intensive Care Unit (NICU), with sepsis being among the most common causes of severe neonatal thrombocytopenia. It is unclear whether decreased platelet production or increased platelet consumption contributes to thrombocytopenia of septic neonates. To answer this question, we evaluated the effects of sepsis on neonatal thrombopoiesis using a panel of tests. This prospective case-control study was conducted on 50 neonates with culture-proven sepsis admitted to NICU at the Pediatrics Department, Ain Shams University Hospitals. Thirty healthy newborns were included as controls. The enrolled neonates were subjected to detailed history taking, thorough clinical examination, and laboratory investigations including complete blood count, C-reactive protein, blood cultures, and tests of thrombopoiesis; namely serum thrombopoietin (TPO) assay, flow cytometric analysis of reticulated platelet percentage (RP%), and calculation of absolute RP counts. Septic neonates comprised 24 males and 26 females with a mean gestational age of 36.0 ± 3.1 weeks. Twenty-eight (56%) of the septic neonates were thrombocytopenic (platelets < 150 000/µl). While platelet and RP counts were decreased, TPO and RP% were increased in septic neonates compared to healthy controls. Neonates with Gram-negative sepsis had the lowest platelet and RP counts and the highest TPO and RP% followed by those with fungal septicemia. Platelet counts showed inverse correlations with TPO and RP% and direct correlation with RP count. Our findings suggest that neonates respond to sepsis by up-regulating thrombopoiesis, where thrombocytopenia ensues when the rate of platelet consumption exceeds the rate of platelet production. Simultaneous measurements of serum TPO levels and RP% are helpful in discriminating hyperdestructive from hypoplastic thrombocytopenia among septic neonates.

Immature and absolute platelet count changes and thrombocytopenia in malignant glioma

BACKGROUND

Temozolomide (TMZ) is commonly used for the therapy of malignant glioma and induces thrombocytopenia in a fraction of patients. Currently, no biomarkers predicting TMZ-induced thrombocytopenia are available. In this study, we investigated whether changes in platelet count (PLT) or the immature platelet fraction (IPF) may serve as predictor of TMZ-induced thrombocytopenia in malignant glioma patients.

METHODS

 We prospectively included 52 malignant glioma patients receiving TMZ-containing therapy regimens in this study. Platelet counts and IPF were determined at each clinical follow-up visit (weekly during concomitant radiochemotherapy or at least monthly during TMZ monotherapy) using the Sysmex XE-2100 system. We explored the diagnostic utility of PLT change/day and IPF change/day from the last to the current follow-up visit for the prediction of clinically relevant thrombocytopenia (PLT < 100·000 μl(-1) ) at the next follow-up visit.

RESULTS

Relevant thrombocytopenia was observed in 10 of 234 occasions. The areas under the receiver operating characteristic curves for PLT absolute change/day, PLT relative change/day and IPF relative change/day were 0·675, 0·703 and 0·663, respectively. The Youden indices (maximum sum of sensitivity and specificity minus one) were 0·31, 0·39, and 0·29, respectively. The corresponding positive predictive values were 16%, 57%, and 6·7%, and the negative predictive values were 97%, 97%, and 98%, respectively.

CONCLUSIONS

The rather moderate diagnostic potential of our data indicate that the time course of PLT counts and IPF measured at routine clinical follow-up are not useful for the prediction of thrombocytopenia in glioma patients treated with TMZ.

Does occupational exposure to low-dose ionizing radiation affect bone marrow thrombopoiesis?

Background

The biological effects of high levels of radiation exposure are fairly well known, but the effects of low levels of radiation are more difficult to determine because the deterministic effects do not occur at these levels.

Methods

In order to assess the risk of this exposure on BM thrombopoiesis, we measured reticulated platelets (RP) by flow cytometry in 14 hospital workers (12 technicians and 2 nurses) exposed to low level ionizing radiation in Radiotherapy Department in South Egypt Cancer Institute.

Results

There are significant difference in the percentage of RP in the peripheral circulation of the workers (p = .008) and no significant difference in the proportion of other blood elements in the peripheral circulation.

Conclusions

We think that measuring RP by flow cytometry is a rapid, non-invasive method to asses an early affection of thrombopoiesis. This type of monitoring may be used as an indicator to detect early BM affection and to demand more controls in radiation protection.

"Message in the platelet"--more than just vestigial mRNA!

Although mammalian platelets are anucleated cells, a number of studies have shown that they retain a pool of messenger RNA (mRNA) carried over from the megakaryocyte during thrombopoiesis. Platelet mRNA was originally thought to be relatively unstable and short-lived within the youngest cells and has been used as a potential marker of platelet turnover. In this article we will discuss both theoretical and methodological issues related to the measurement of these younger, "reticulated platelets". A key question relating to platelet mRNA is also whether it has any functional relevance other than a marker of platelet immaturity. Evidence going back more than 30 years suggests that platelets can biosynthesize proteins. However, it is only very recently that the nature and specificity of platelet mRNA has been examined in any detail. Difficulties in obtaining pure platelet mRNA, free of contamination from other cells has added to the complexity of unravelling this story. However, there is now clear evidence that platelets contain small but significant levels of message for a variety of proteins. The platelet mRNA pool is much richer and more diverse than previously thought and recent data suggests that regulated synthesis of a selected number of proteins can be induced on platelet activation. The full complexity of the platelet genome is now just being revealed and may open the possibility for improved diagnosis and therapy of many haemostatic and thrombotic disorders.

[Relationship between reticulated platelets and megacaryocyte number in thrombocytopenic patients]

BACKGROUND AND INTRODUCTION

Marrow aspiration is a test that helps the pathogenic diagnosis of thrombocytopenia. Our goal was to analyze the correlation between reticulated platelets (RP) values in peripheral blood with megakaryocytic number in bone marrow in a group of thrombocytopenic patients.

PATIENTS AND METHODS

Prospective observational study in thrombocytopenic patients, between June 2002 and June 2005. RP determination was performed by flow cytometry using whole blood. We used a monoclonal anti-glycoprotein-IIIa antibody (CD61PerCP) for platelet identification and orange thiazole (Retic-count) as platelet mRNA stain. Marrow study was conducted by marrow aspiration.

RESULTS

RP were measured in 54 thrombocytopenic patients with bone marrow study. Three were excluded from the study. Thirty-two patients had central thrombocytopenia with diminished megakaryocytes (MK) and/or dysplasia, mean of RP 9.5% (CI 95%:5.6%-13.4%). Thirteen patients had high MK,mean of RP 25.7%(CI 95%:13.1%-38.3%). Six patients had normal MK, mean of RP 13.6% (CI 95%:0.6%-26.8%). There were differences between the group of increased MK and the group of central thrombocytopenias (p=0001). A value of RP>or=11% showed a sensitivity of 70% and specificity of 81% for the diagnosis of marrow aspirate with increased MK.

CONCLUSIONS

RP are an indirect marker of megakaryocyte number in bone marrow. A value of RP>or=11% in patients with thrombocytopenia, especially with an acute onset, would indicate regenerative thrombocytopenia, while in the presence of low levels of RP a marrow aspiration should be performed.

Reticulated platelets as a screening test to identify thrombocytopenia aetiology

BACKGROUND

Thrombocytopenia is a common haematological abnormality and no simple diagnostic test is available to diagnose thrombocytopenia pathogenesis.

AIM

To evaluate sensitivity and specificity of reticulated platelets (RP) as a diagnostic test for thrombocytopenia with increased thrombopoietic activity.

DESIGN

Prospective observational study in thrombocytopenic patients.

METHODS

A direct, whole-blood, dual-labelling flow cytometric method was used. Direct, whole-blood double coverage was achieved using a monoclonal anti-glycoprotein (GP)-III antibody (CD61 PerCP) for platelet identification and thiazole orange (Retic-count) as platelet mARN stain.

RESULTS

RP were measured in 101 thrombocytopenic patients and 104 non-thrombocytopenic controls. The mean RP percentage in 60 thrombocytopenic patients with no increased thrombopoietic activity was 7.5% (CI for 95%: 5.2-9.7) and RP absolute number was 3.2 x 10(9)/l (CI for 95%: 2.1-4.3). The mean RP percentage in 41 thrombocytopenic patients with increased thrombopoietic activity was 30.3% (CI for 95%: 25.1-35.5) and RP absolute number was 6.2 (CI for 95%: 4.8-7.7). The RP percentage cut-off for a diagnosis of thrombocytopenia with increased thrombopoietic activity was 11% [sensitivity 93%, specificity 85%, positive predictive value (PPV) 83%, negative predictive value (NPV) 95%].

CONCLUSION

RP measurement by flow cytometry, directly from whole-blood, is a useful screening test to differentiate between thrombocytopenia with high or low thrombopoietic activity. A RP percentage in excess of 11%, has a high sensitivity and good specificity for a diagnosis of thrombocytopenia with increased thrombopoietic activity.