Immature platelet fraction: establishment of a reference interval and diagnostic measure for thrombocytopenia

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).

Prothrombotic Phenotype in COVID-19: Focus on Platelets

COVID-19 infection is associated with a broad spectrum of presentations, but alveolar capillary microthrombi have been described as a common finding in COVID-19 patients, appearing as a consequence of a severe endothelial injury with endothelial cell membrane disruption. These observations clearly point to the identification of a COVID-19-associated coagulopathy, which may contribute to thrombosis, multi-organ damage, and cause of severity and fatality. One significant finding that emerges in prothrombotic abnormalities observed in COVID-19 patients is that the coagulation alterations are mainly mediated by the activation of platelets and intrinsically related to viral-mediated endothelial inflammation. Beyond the well-known role in hemostasis, the ability of platelets to also release various potent cytokines and chemokines has elevated these small cells from simple cell fragments to crucial modulators in the blood, including their inflammatory functions, that have a large influence on the immune response during infectious disease. Indeed, platelets are involved in the pathogenesis of acute lung injury also by promoting NET formation and affecting vascular permeability. Specifically, the deposition by activated platelets of the chemokine platelet factor 4 at sites of inflammation promotes adhesion of neutrophils on endothelial cells and thrombogenesis, and it seems deeply involved in the phenomenon of vaccine-induced thrombocytopenia and thrombosis. Importantly, the hyperactivated platelet phenotype along with evidence of cytokine storm, high levels of P-selectin, D-dimer, and, on the other hand, decreased levels of fibrinogen, von Willebrand factor, and thrombocytopenia may be considered suitable biomarkers that distinguish the late stage of COVID-19 progression in critically ill patients.

Unique characteristics of new complete blood count parameters, the Immature Platelet Fraction and the Immature Platelet Fraction Count, in dengue patients

The advanced platelet parameters Immature Platelet Fraction and Immature Platelet Fraction Count have been implemented in clinical practice as measures of thrombopoietic activity, mainly in hematologic disorders that cause thrombocytopenia. The purpose of this observational study was to examine thrombopoiesis as reflected by these 2 new CBC parameters in patients infected with dengue. The study was conducted in infectious disease referral hospital in Metro Manila, the Philippines. We enrolled hospitalized patients at admission who were diagnosed with acute dengue or community acquired bacterial infection (CABI). Immature Platelet Fraction (IPF) and Immature Platelet Fraction Count were evaluated at admission and during hospitalization. A total of 606 patients were enrolled from May 1, 2017 to June 1, 2018. The participants consisted of 152 patients with dengue infection, 180 confirmed CABI, and 274 suspected CABI patients. At admission, the percent IPF (IPF%) of the patients with dengue was significantly higher than that of the confirmed CABI patients (median 3.7% versus 1.9%; p <0.001). In a time course evaluation, there was no significant difference of IPF% between the patients with dengue infection and the confirmed CABI patients in the febrile phase (median 1.9% versus 2.4%; p = 0.488), however, the IPF% of the patients with dengue infection increased to be significantly higher than that of the confirmed CABI patients in the critical phase (median 5.2% versus 2.2%; p <0.001). Our study elucidated the unique characteristics and time-course trends of IPF percent and number (IPF#) in the patients with dengue infection. IPF% and IPF# are potentially valuable parameters in dengue and further investigation is required for the optimal use in clinical practice.

Immature Platelet Fraction: Its Clinical Utility in Thrombocytopenia Patients

Objectives Etiology of thrombocytopenia is multifactorial and its pathogenesis should be distinguished for appropriate management. Newly formed immature platelets are called reticulated platelets (RPs) and can be estimated in peripheral blood using automated hematology analyzers, which express them as immature platelet fraction (IPF). In the present study we intend to assess and establish the clinical utility of IPF in differentiating the two major causes of thrombocytopenia-decreased production and increased destruction of platelets-along with determining its significance in monitoring patients with thrombocytopenia. Materials and Methods Sixty-one cases of thrombocytopenia and 101 healthy controls with normal platelet count were included in the study. IPF and all the other usual blood cell parameters were measured using a fully automated hematology analyzer. Based on the pathogenesis of thrombocytopenia, the cases were divided into groups and the difference in IPF value between the groups was evaluated. Results The reference range of IPF among healthy controls was estimated to be 0.7 to 5.7%. The mean IPF was significantly higher in patients with increased peripheral destruction of platelets (13.4%) as compared to patients with decreased production of platelets (4.6%). The optimal cutoff value of IPF for differentiating patients with increased peripheral destruction of platelets from patients with decreased production of platelets was 5.95% with a sensitivity of 88% and specificity of 75.9%. Conclusion Measurement of IPF is useful for detecting evidence of increased platelet production and helps in the initial evaluation of thrombocytopenia patients. It is a novel diagnostic method which can be used to differentiate patients with thrombocytopenia due to increased destruction of platelets from patients with thrombocytopenia due to bone marrow failure/suppression.

The immature platelet fraction affects the efficacy of platelet rich plasma therapy for knee osteoarthritis

Introduction

Platelet-rich plasma (PRP) therapy is used to treat pathological conditions such as degenerative inflammatory diseases including osteoarthritis (OA) by enhancing tissue repair and promoting anti-inflammatory effects. Although PRP therapy for patients with knee OA improved pain and functional scores, the association of clinical outcomes and quality of PRP including cell composition and concentration is unclear.

Methods

Therefore, this study analyzed blood cell counts, including the immature platelet fraction (IPF), in peripheral blood and PRP of 144 patients with knee OA who underwent PRP therapy. The mean leukocyte and platelet concentrations in whole blood and PRP were analyzed using an XN-1000 automated hematology analyzer. Visual analogue scale (VAS) scores and knee injury and osteoarthritis outcome scores (KOOS) before and 1 month after a single PRP injection were also determined.

Results

Higher platelet and lower leukocyte concentration rates were observed in PRP compared with whole blood. The platelet concentration in whole blood was negatively correlated with VAS improvement. The percentage of IPF (IPF%) in whole blood was positively correlated with VAS improvement and KOOS (pain) improvement, whereas the IPF% in PRP tended to correlate with VAS improvement. Furthermore, multivariate logistic regression demonstrated the high IPF% in whole blood was significantly associated with VAS improvement. The low percentage of neutrophil (neutrophil%) in PRP was significantly associated with the VAS improvement and KOOS (ADL) improvement.

Conclusions

Therefore, PRP efficacy for OA might depend on the patient's biological status.

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High percentage of IPF (IPF%) in whole blood was significantly associated with VAS improvement.

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Low neutrophil% in PRP was significantly associated with VAS improvement and KOOS (ADL) improvement.

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The PRP efficacy for knee OA might depend on the patient's biological status.

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.

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.

Evaluation of Immature Platelet Fraction in Lower Respiratory Tract Infections: A Retrospective Study

Introduction

Immature platelet fraction (IPF) is a parameter of an automated hematologic analyzer and is related to platelet size and cytoplasmic RNA content. It reflects thrombopoiesis and is often used as the marker of platelet activity. IPF has been evaluated mostly in hematologic disorders and has also been evaluated in patients with gestational hypertension, sepsis, autoimmune diseases and in hospitalised patients with neutrophilia. Platelets, asides from the maintenance of hemostasis, release inflammatory mediators that can modify leukocyte and endothelial responses to various inflammatory stimuli. Lower respiratory tract infections are the leading cause of death from infections worldwide. The role of platelets in lower respiratory tract infections has been reported in many studies. IPF, which is related to platelet activation, has not been evaluated in patients with lower respiratory tract infections.

Methods

The study involved patients who fulfilled the criteria of community-acquired pneumonia (CAP) and aspiration pneumonia (AP). In addition, age and sex-matched healthy controls were involved. Whole blood samples were collected from healthy controls and from the patients on admission. The mean IPF% and C-reactive protein (CRP) levels were measured in patients with CAP, in patients with AP and in healthy controls. The mean IPF% values in patients with infection were compared to mean IPF% values in healthy controls. The mean IPF% values were compared to mean CRP levels in patients with infection. Additionally, the mean IPF% values in patients that died in the first 14 days were compared to the mean IPF% values in patients that were alive. The statistical analysis of data was performed with the Statistical Package for the Social Sciences (SPSS) for Windows, Version 13.0 (SPSS Inc, Chicago, IL). 

Results

The study population consisted of 45 patients (27 patients with CAP and 18 patients with AP), 27 males and 18 females, with a mean age of 72.11 ± 16.4 years and 39 healthy controls, 22 males and 17 females with a mean age of 64.2 ± 14.8 years. The mean CRP levels in patients with infection were 155.2±119.1 mg/dl. The mean IPF% value of patients with infection was 2.76 ± 2.27 and the mean IPF% value of controls was 1.72 ± 0.77 (p < 0.006). The IPF% value in patients with CAP was 2.55 ± 2.02 and in patients with AP 3.07 ± 2.64 (p = 0.595). The mean IPF% value in patients with infection had no linear correlation with CRP value in these patients (r = 0.076, p = 0.62). The mean IPF% value in all patients that died in the first 14 days was 3.75 ± 2.44 and the mean IPF% value in all patients alive was 2.35 ± 2.11 (p = 0.06). The mean IPF% value in patients with CAP who died in the first 14 days of hospitalisation was 5.54 ± 3.17 and in patients with CAP who were alive was 1.87 ± 0.72 (p = 0.06). The mean IPF% value in patients with AP who died was 2.63 ± 0.85 and in patients with AP who were alive was 3.41 ± 3.51 (p = 0.554).

Conclusions

Mean IPF% value is greater in patients with lower respiratory tract infections, including CAP and AP, compared to healthy controls. There is no linear correlation between IPF values and CRP values in patients with lower respiratory tract infections. In addition, there is a difference in mean IPF% value between patients who died in the first 14 days of hospitalisation compared to those who were alive, but not statistically significant.

Immature platelet fraction based diagnostic predictive scoring model for immune thrombocytopenia

BACKGROUND/AIMS

The diagnosis of immune thrombocytopenia (ITP) is based on clinical manifestations and there is no gold standard. Thus, even hematologic malignancy is sometimes misdiagnosed as ITP and adequate treatment is delayed. Therefore, novel diagnostic parameters are needed to distinguish ITP from other causes of thrombocytopenia. Immature platelet fraction (IPF) has been proposed as one of new parameters. In this study, we assessed the usefulness of IPF and developed a diagnostic predictive scoring model for ITP.

METHODS

We retrospectively studied 568 patients with thrombocytopenia. Blood samples were collected and IPF quantified using a fully-automated hematology analyzer. We also estimated other variables that could affect thrombocytopenia by logistic regression analysis.

RESULTS

The median IPF was significantly higher in the ITP group than in the non-ITP group (8.7% vs. 5.1%). The optimal cut-off value of IPF for differentiating ITP was 7.0%. We evaluated other laboratory variables via logistic regression analysis. IPF, hemoglobin, lactate dehydrogenase (LDH), and ferritin were statistically significant and comprised a diagnostic predictive scoring model. Our model gave points to each of variables: 1 to high hemoglobin (> 12 g/dL), low ferritin (≤ 177 ng/ mL), normal LDH (≤ upper limit of normal) and IPF ≥ 7 and < 10, 2 to IPF ≥ 10. The final score was obtained by summing the points. We defined that ITP could be predicted in patients with more than 3 points.

CONCLUSION

IPF could be a useful parameter to distinguish ITP from other causes of thrombocytopenia. We developed the predictive scoring model. This model could predict ITP with high probability.

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.

Immature platelet fraction related parameters in the differential diagnosis of thrombocytopenia

The pathogenesis of thrombocytopenia can be divided into increased destruction (ID) of platelets in the peripheral blood and decreased production (DP) of platelets in the bone marrow. This study aimed to analyze the efficacy of immature platelet fraction (IPF) related parameters, including the IPF count (IPF#), IPF percentage (IPF%) and highly fluorescence IPF percentage (H-IPF%), measured by XN-9000, in the differential diagnosis of thrombocytopenia. One hundred and twenty healthy volunteers were enrolled in the healthy control (HC) group, and 180 thrombocytopenia patients were grouped into either the increased destruction (ID) group or the decreased production (DP) group according to their final diagnosis. IPF# was significantly lower in the DP group than in the ID and HC groups (P < .01). Among the three groups, the ID group had the highest IPF% and H-IPF%, and the HC group had the lowest IPF% and H-IPF%. The differences between the three groups were all statistically significant (P < .01). In differentiating the ID patients from the DP patients, the areas under the operating characteristics curve of IPF#, IPF% and H-IPF% were 0.859, 0.944 and 0.930, respectively. False positive rates were below 0.04 when IPF#, IPF% and H-IPF% were above 2.65, 7.55 and 2.35, respectively. IPF related parameters showed high efficacy in the differential diagnosis of thrombocytopenia. However, due to the small numerical values of the IPF related parameters in some thrombocytopenia patients, the fluctuations of IPF% and H-IPF% should also be taken into consideration. Though H-IPF% is a new parameter, its effectiveness in the differential diagnosis of thrombocytopenia is not better than IPF%'s.

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 interval for immature platelet fraction on Sysmex XN haematology analyser in adult population

Introduction

The Sysmex XN-series haematology analyser has newly adopted a fluorescent channel to measure immature platelet fraction (IPF). To promote the clinical utility of this promising parameter, establishing a reliable reference interval is mandatory. According to previous studies, IPF values may be affected by the employed analyser and the ethnic background of the individual, but no differences seem to be found between individuals’ genders. Therefore, this study aimed to define the reference interval for IPF in a Spanish population following Clinical and Laboratory Standard Institute (CLSI) guidelines.

Materials and methods

A total of 153 healthy Caucasian adults from Spain met the inclusion criteria. IPF measurement was performed by means of a Sysmex XN-2000 haematology analyser. A non-parametric percentile method was used to calculate the reference intervals in accordance with CLSI guidelines.

Results

The obtained reference interval for IPF on the Sysmex XN-2000 was 1.6–9.6% (90% confidence intervals (CIs) were 1.5–1.8 and 9.3–11.5, respectively). No significant gender difference in IPF reference intervals was observed (P = 0.101).

Conclusions

This study provides, for the first time, a reference interval for IPF using a Sysmex XN-2000 in a Spanish population, ranging from 1.6 to 9.6%. These data are needed to evaluate platelet production in several conditions such as thrombocytopenia, inflammatory states and cardiovascular diseases, as well as for future research.

Immature Platelet Count Levels as a Novel Quality Marker in Plateletpheresis

The efficiency of plateletpheresis was improved owing to new developments in automated cell separators in the past decades. Nowadays multiple units of plateletpheresis products can be taken per collection from single donor and new parameters such as immature platelet fraction (IPF), immature platelet count (IPC) can be detected practically by automated hematology analyzers. Our aim is to find out a new quality parameter for evaluation of plateletpheresis by analyzing the platelet indices of donor and also to predict platelet recovery in recipients thereby preventing unnecessary platelet transfusion. In this study 104 platelet apheresis procedures were performed on the Trima Accel cell separator. Complete blood counts of donors and recipients were analyzed by Sysmex XN-1000 automated blood cell counter by means of quality parameters such as platelet count, IPF, IPC, mean platelet volume, platelet distribution width. We analyzed these parameters in the follow up after the transfusion of plateletpheresis and evaluated them as quality markers in the assessment of plateletpheresis effectiveness. For recipients of both single and double unit apheresis platelet transfusions, the pre-apheresis donor IPC correlated significantly with 1st and 24th hour recipient IPC values (p values < 0.05 for all comparisons). A-IPC as well as % change in IPF can be used to determine the quality of plateletpheresis in conjunction with platelet number in terms of evaluation of donors and also in the follow up of recipients undergoing platelet transfusion.

Establishment of the Reference Intervals of Lymphocyte Function in Healthy Adults Based on IFN-γ Secretion Assay upon Phorbol-12-Myristate-13-Acetate/Ionomycin Stimulation

The function of lymphocytes is the key to reflect the immune status of hosts. Evaluation of lymphocyte function is a useful tool to monitor the effect of immunosuppressive treatment and predict the prognosis of immune-mediated diseases (e.g., cancer, autoimmune diseases, and infectious diseases). As the lymphocytes have various activities, such as activation, cytotoxicity, and cytokine secretion, it is a challenge to evaluate the function of lymphocytes in clinical practice and the reference intervals (RIs) of lymphocyte function are rarely reported. The present study showed that the secretion of IFN-γ was well correlated with the activation, chemotaxis, and cytotoxicity of CD4⁺, CD8⁺ T cells, and NK cells, which suggests that IFN-γ production can be used as a symbol of lymphocyte function. We therefore created a simple method to detect the function of CD4⁺, CD8⁺ T cells, and NK cells simultaneously according to IFN-γ secretion by using whole blood instead of peripheral blood mononuclear cells. We further established the RIs of lymphocyte function (CD4⁺ T cells: 15.31-34.98%; CD8⁺ T cells: 26.11-66.59%; NK cells: 39.43-70.79%) in healthy adults. This method showed good reproducibility for the evaluation of lymphocyte function. The established RIs were suitable for use in other centers based on the validation data. We also validated the RIs in individuals with different immune status, and the results showed that kidney transplant recipients and infants (0-1 year) had a decreased lymphocyte function, whereas T cells in systemic lupus erythematosus patients exhibited an opposite trend. Overall, we have successfully established the RIs of lymphocyte function in healthy adults in a simple way, which might be of important clinical value in the diagnosis, monitoring, and prognosis of immune-related diseases.

Utility of the immature platelet fraction in pediatric immune thrombocytopenia: Differentiating from bone marrow failure and predicting bleeding risk

BACKGROUND

Differentiating childhood immune thrombocytopenia (ITP) from other cause of thrombocytopenia remains a diagnosis of exclusion. Additionally factors that predict bleeding risk for those patients with ITP are currently not well understood. Previous small studies have suggested that immature platelet fraction (IPF) may differentiate ITP from other causes of thrombocytopenia and in combination with other factors may predict bleeding risk.

METHODS

We performed a retrospective chart review of thrombocytopenic patients with an IPF measured between November 1, 2013 and July 1, 2015. Patients were between 2 months and 21 years of age with a platelet count <50 × 10⁹ /l. Each patient chart was reviewed for final diagnosis and bleeding symptoms. A bleeding severity score was retrospectively assigned.

RESULTS

Two hundred seventy two patients met inclusion criteria, 97 with ITP, 11 with bone marrow failure (BMF), 126 with malignancy, and 38 with other causes of thrombocytopenia. An IPF > 5.2% differentiated ITP from BMF with 93% sensitivity and 91% specificity. Absolute immature platelet number (AIPN) was significantly lower in ITP patients with severe to life-threatening hemorrhage than those without, despite similar platelet counts. On multivariate analysis, an IPF < 10.4% was confirmed as an independent predictor of bleeding risk at platelet counts <10 × 10⁹ /l in patients with ITP.

CONCLUSIONS

IPF measurement alone has utility in both the diagnosis of ITP and identifying patients at increased risk of hemorrhage. Further study is required to understand the pathophysiological differences of ITP patients with lower IPF/AIPN.

Mean Platelet Volume and Immature Platelet Fraction in Autoimmune Disorders

Mean platelet volume (MPV), measured using automated blood analysers, has been appraised as a potential biomarker in cardiovascular disease, diabetes mellitus, and cancer. The test, a useful tool in differentiation of thrombocytopenic states, has now been carried out for autoimmune disorders, but data are yet scarce. Controversial results have been obtained in systemic and organ-specific autoimmune disorders. Another test, the immature platelet fraction (IPF) reflects the amount of young, reticulated platelets. IPF is calculated by automated hematology analysis or flow cytometry, and it is usually high in patients with rapid platelet destruction. For both MPV and IPF, standardization of cutoff is a major need. In this review, we focus the current applicability of MPV and IPF as biomarkers in patients with autoimmune diseases.

Immature platelet fraction in septic patients: clinical relevance of immature platelet fraction is limited to the sensitive and accurate discrimination of septic patients from non-septic patients, not to the discrimination of sepsis severity

Background

The immature platelet fraction (IPF) reflects the degree of reticulated platelets. We evaluated performances of IPF as a biomarker for the discrimination of septic patients from non-septic patients and sepsis severity.

Methods

Total 312 patients admitted between March and July 2013 were enrolled and samples were obtained at admission. Lactate (LA), procalcitonin (PCT), C-reactive protein (CRP), immature granulocyte fraction (IG), immature reticulocyte fraction (IRF), and IPF were analyzed as sepsis biomarkers and their performances were compared.

Results

The performance of IPF (area under the curve [AUC]=0.868) in the discrimination of septic patients from non-septic patients was comparable to PCT/CRP/LA/IG (AUC=0.923/0.940/0.781/0.812, P=0.233/0.106/0.186/0.353, respectively), and was significantly better than the IRF (AUC=0.658, P=0.007). Sensitivity (89.8%, 95% confidence interval [CI] 84.9-99.8%) and accuracy (83.2%, 95% CI 78.8-90.0%) of IPF were the best among all biomarkers. The performance of IPF in discriminating septic patients from non-septic patients with local infection showed similar results. However, the IPF could not efficiently discriminate sepsis severity (AUC=0.599), similar to other biomarkers (AUC=0.519-0.752).

Conclusions

The IPF possessed high sensitivity/accuracy in discriminating septic patients from non-septic patients, regardless of local infection status. However, the IPF did not efficiently discriminate sepsis severity. The clinical relevance of IPF as a sepsis biomarker is, therefore, limited to sensitive and accurate discrimination of septic patients from non-septic patients, not discrimination of sepsis severity.

Reference interval for immature platelet fraction on Sysmex XN hematology analyzer: a comparison study with Sysmex XE-2100

BACKGROUND

Recently introduced hematology analyzer, the Sysmex XN modular system (Sysmex, Kobe, Japan), has newly adopted a florescent channel to detect platelets and immature platelet fraction (IPF). This study aimed to establish new reference intervals for %-IPF and absolute number of IPF (A-IPF) on Sysmex XN. Platelet counts, %-IPF, and A-IPF were also compared between Sysmex XN and XE-2100 systems (Sysmex).

METHODS

Except outliers, blood samples from 2104 healthy individuals and 140 umbilical cord blood were analyzed using both Sysmex XN and XE-2100. The results of two systems were compared using Bland-Altman plot. The reference intervals for %-IPF and A-IPF were defined using non-parametric percentile methods according to the Clinical and Laboratory Standard Institute guideline (C28-A3).

RESULTS

The platelet counts, %-IPF, and A-IPF showed non-parametric distributions. The mean difference between Sysmex XN and XE-2100 in healthy individuals revealed a positive bias in platelets (+8.0×109/L), %-IPF (+1.2%), and A-IPF (+3.0×109/L). The reference intervals for %-IPF and A-IPF on Sysmex XN were: 1.0%-7.3% and 2.49-15.64×109/L in healthy individuals; and 1.0%-4.4% and 2.94-12.82×109/L in umbilical cord blood.

CONCLUSIONS

This large-scale study demonstrates a clear difference of platelet counts and IPF between Sysmex XN and XE-2100. The new reference intervals for IPF on Sysmex XN would provide fundamental data for clinical practice and future research.

Age and gender effects on 15 platelet phenotypes in a Spanish population

INTRODUCTION

Several studies have analysed the platelet parameters in human blood, nevertheless there are no extensive analyses on the less common platelet phenotypes. The main objective of our study is to evaluate the age and gender effects on 15 platelet phenotypes.

METHODS

We studied 804 individuals, ranging in age from 2 to 93 years, included in the Genetic Analysis of Idiopathic Thrombophilia 2 (GAIT 2) Project. The 15 platelet phenotypes analysed were the platelets counts, platelet volumes, plateletcrits, immature platelet fraction (IPF) and platelet function assay (PFA). A regression-based method was used to evaluate the age and gender effects on these phenotypes.

RESULTS

Our results were consistent with the previously reported results regarding platelet counts and plateletcrit (PCT). They showed a decrease with increasing age. The mean platelet volume (MPV), platelet distribution width (PDW) and platelet-large cell ratio (P-LCR) increased with age, but did not present any gender effect. All the IPF phenotypes increased with age, whereas the PFA phenotypes did not show any relation to age or gender.

DISCUSSION

To sum up, our study provides a comprehensive analysis of the age and gender effects on the platelet phenotypes in a family-base sample. Our results suggest more reasonable age stratification into two distinct groups: childhood, ranging from 2 to 12 years, and the mature group, from 13 to 93 years. Moreover, the PFA phenotypes were maintained constant while the platelet counts, the MPV and IPF levels vary with age.

Absolute immature platelet count dynamics in diagnosing and monitoring the clinical course of thrombotic thrombocytopenic purpura

BACKGROUND

Thrombotic thrombocytopenic purpura (TTP) is a life-threatening diagnosis requiring prompt initiation of therapeutic plasma exchange (TPE). Measurement of immature platelet (PLT) fraction (%-IPF) differentiates PLT consumption or destruction from hypoproduction.

STUDY DESIGN AND METHOD

Our study evaluated %-IPF changes over the course of TTP treated with TPE and as a measure of treatment efficacy. Eleven idiopathic TTP patients, two human immunodeficiency virus (HIV)-associated TTP patients, and five non-TTP patients with thrombocytopenia were enrolled into our study. All patients were treated with TPE and had ADAMTS13 activity measured.

RESULTS

All idiopathic TTP patients had a significantly increased %-IPF and decreased absolute immature PLT count (A-IPC) and PLT count at presentation. An A-IPC value of less than 5 × 10(9) /L at presentation has 84.6% sensitivity, 80% specificity, and 91.7% positive predictive value for diagnosing TTP. A concurrent steady decline in %-IPF and increased PLT counts toward normal was observed in TTP patients undergoing TPE. The A-IPC, however, showed an increase and decrease curve that was not seen in the two HIV-associated TTP patients with no response to TPE and the five non-TTP patients. More importantly, reaching an A-IPC ratio of 3 compared to baseline value during TPE can readily differentiate idiopathic TTP from the other two groups and is correlated with good clinical responses to TPE. An abrupt increase of A-IPC during TPE was also noted in a TTP patient who relapsed 3 days before PLT count decrease. A-IPC is positively correlated with ADAMTS13 activity at presentation but negatively correlated with ADAMTS13 activity during recovery.

CONCLUSION

A-IPC should be routinely analyzed for diagnosing and monitoring TTP patients.

Haematological reference intervals in a multiethnic population

INTRODUCTION

Similar to other populations, full blood count reference (FBC) intervals in Malaysia are generally derived from non-Malaysian subjects. However, numerous studies have shown significant differences between and within populations supporting the need for population specific intervals.

METHODS

Two thousand seven hundred twenty five apparently healthy adults comprising all ages, both genders and three principal races were recruited through voluntary participation. FBC was performed on two analysers, Sysmex XE-5000 and Unicel DxH 800, in addition to blood smears and haemoglobin analysis. Serum ferritin, soluble transferrin receptor and C-reactive protein assays were performed in selected subjects. All parameters of qualified subjects were tested for normality followed by determination of reference intervals, measures of central tendency and dispersion along with point estimates for each subgroup.

RESULTS

Complete data was available in 2440 subjects of whom 56% (907 women and 469 men) were included in reference interval calculation. Compared to other populations there were significant differences for haemoglobin, red blood cell count, platelet count and haematocrit in Malaysians. There were differences between men and women, and between younger and older men; unlike in other populations, haemoglobin was similar in younger and older women. However ethnicity and smoking had little impact. 70% of anemia in premenopausal women, 24% in postmenopausal women and 20% of males is attributable to iron deficiency. There was excellent correlation between Sysmex XE-5000 and Unicel DxH 800.

CONCLUSION

Our data confirms the importance of population specific haematological parameters and supports the need for local guidelines rather than adoption of generalised reference intervals and cut-offs.

Steady increment of immature platelet fraction is suppressed by irradiation in single-donor platelet components during storage

Circulating immature platelet fraction (IPF) reflects real-time thrombopoiesis and correlates with platelet recovery from thrombocytopenic presentations. To understand the dynamics of IPF in platelet transfusions, we quantified the %-IPF in single-donor platelet components (SDP) during prolonged storage. %-IPF significantly increased from baseline by day 5 post-donation. Absolute IPF counts (A-IPC) had similar significant increments. However, gamma-irradiation suppressed the increments of %-IPF and A-IPC by >50%. Ultrastructural analysis of SDP units at day 10 showed well preserved morphology of immature platelets. Our findings suggest that IPF might actively expand ex-vivo and may have a longer shelf life than their mature counterparts. Closer study of IPF may be of critical clinical importance for transfusion practices.

Reference intervals of reticulated platelets and other platelet parameters and their associations

CONTEXT

Reticulated platelets are platelets recently released from the bone marrow, and they can serve as a noninvasive indicator of recent megakaryopoietic activity. Widespread clinical use has been hampered by laborious methods and lack of standardization. Recently, a fully automated method was released on the Abbott CELL-DYN Sapphire hematology analyzer.

OBJECTIVE

To establish reference ranges for reticulated platelets. Secondary aims were to investigate associations between reticulated platelets and other platelet parameters like mean platelet volume, plateletcrit, and platelet distribution width.

DESIGN

Reticulated platelets and other platelet parameters were measured in an unselected cohort of 8089 subjects visiting a primary health care laboratory. The reticulated platelet data were analyzed using the Bhattacharya technique. In addition, a nonparametric method was used in selected subjects with normal platelet counts for providing reference ranges.

RESULTS

Reticulated platelets ranged from 0.4% to 6.0% or from 1 to 18 × 10(3)/μL. Reticulated platelets increased significantly with the subjects' age. Statistically, males had slightly higher values than females, but the differences were negligible. Reticulated platelets were positively correlated with platelet count and negatively with mean platelet volume.

CONCLUSIONS

Reference ranges have been established for reticulated platelets as measured on the CELL-DYN Sapphire hematology analyzer. There were no relevant differences between the sexes, but there was a clear effect of age. An individual's reticulated platelets are associated with the platelet count as well as mean platelet volume.

Establishment of reference interval for immature platelet fraction

INTRODUCTION

Immature platelet fraction (IPF) is a parameter for reticulated platelets. A high percentage IPF (%-IPF) is indicative of consumptive or recovering thrombocytopenic disorders in contrast to a low %-IPF seen in aplastic states. Absolute IPF (A-IPF) specifically reflects the number of immature platelets in circulation. This study aimed to establish reliable reference intervals for %-IPF and A-IPF.

METHODS

Except outliers, platelet counts and IPF were determined in 2152 healthy individuals (1252 men and 900 women) and 133 umbilical cord blood from healthy full-term neonates using XE-2100 hematology analyzer (Sysmex, Kobe, Japan). The reference intervals for %-IPF and A-IPF were defined using nonparametrical percentile methods according to the Clinical and Laboratory Standard Institute (CLSI) guideline.

RESULTS

Platelets,%-IPF, and A-IPF all showed nonparametrical distributions. In total individuals, the reference intervals for %-IPF and A-IPF were 0.5-3.3% (0.5-3.1% in men; 0.5-3.4% in women) and 1.25-7.02 × 10(9) /L (1.30-6.80 × 10(9) /L in men; 1.21-7.15 × 10(9) /L in women), respectively. The reference intervals for %-IPF and A-IPF in umbilical cord blood were 0.7-3.8% and 1.93-9.7 × 10(9) /L, respectively.

CONCLUSIONS

This study provides the reference interval for IPF, including %-IPF and A-IPF, according to the CLSI guideline. These results could be used as fundamental data for clinical use as well as future researches.

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.

Platelet production and platelet destruction: assessing mechanisms of treatment effect in immune thrombocytopenia

This study investigated the immature platelet fraction (IPF) in assessing treatment effects in immune thrombocytopenia (ITP). IPF was measured on the Sysmex XE2100 autoanalyzer. The mean absolute-IPF (A-IPF) was lower for ITP patients than for healthy controls (3.2 vs 7.8 × 10⁹/L, P < .01), whereas IPF percentage was greater (29.2% vs 3.2%, P < .01). All 5 patients with a platelet response to Eltrombopag, a thrombopoietic agent, but none responding to an anti-FcγRIII antibody, had corresponding A-IPF responses. Seven of 7 patients responding to RhoD immuneglobulin (anti-D) and 6 of 8 responding to intravenous immunoglobulin (IVIG) did not have corresponding increases in A-IPF, but 2 with IVIG and 1 with IVIG anti-D did. This supports inhibition of platelet destruction as the primary mechanism of intravenous anti-D and IVIG, although IVIG may also enhance thrombopoiesis. Plasma glycocalicin, released during platelet destruction, normalized as glycocalicin index, was higher in ITP patients than controls (31.36 vs 1.75, P = .001). There was an inverse correlation between glycocalicin index and A-IPF in ITP patients (r² = -0.578, P = .015), demonstrating the relationship between platelet production and destruction. Nonresponders to thrombopoietic agents had increased megakaryocytes but not increased A-IPF, suggesting that antibodies blocked platelet release. In conclusion, A-IPF measures real-time thrombopoiesis, providing insight into mechanisms of treatment effect.