Pathophysiological significance of simultaneous measurement of reticulated platelets, large platelets and serum thrombopoietin in non-neoplastic thrombocytopenic disorders

Reference guide for the diagnosis of adult primary immune thrombocytopenia, 2023 edition

Primary immune thrombocytopenia (ITP) is an autoimmune disorder characterized by isolated thrombocytopenia due to accelerated platelet destruction and impaired platelet production. Diagnosis of ITP is still challenging because ITP has been diagnosed by exclusion. Exclusion of thrombocytopenia due to bone marrow failure is especially important in Japan because of high prevalence of aplastic anemia compared to Western countries. Hence, we propose a new diagnostic criteria involving the measurement of plasma thrombopoietin (TPO) levels and percentage of immature platelet fraction (RP% or IPF%); 1) isolated thrombocytopenia with no morphological evidence of dysplasia in any blood cell type in a blood smear, 2) normal or slightly increased plasma TPO level (< cutoff), 3) elevated RP% or IPF% (> upper limit of normal), and 4) absence of other conditions that potentially cause thrombocytopenia including secondary ITP. A diagnosis of ITP is made if conditions 1-4 are all met. Cases in which criterion 2 or 3 is not met or unavailable are defined as "possible ITP," and diagnosis of ITP can be made mainly by typical clinical course. These new criteria enable us to clearly differentiate ITP from aplastic anemia and other forms of hypoplastic thrombocytopenia and can be highly useful in clinical practice for avoiding unnecessary bone marrow examination as well as for appropriate selection of treatments.

Immature platelet fraction in rheumatoid arthritis with interstitial lung disease

BACKGROUND

Platelets have an effect on the hemostatic defense of the lung. Immature platelet fractions (iPF) reflects the number of young platelets containing ribonucleic acid in the circulation and real-time production. Information about their roles in rheumatic diseases is limited and there are no studies on iPF in RA with interstitial lung disease (ILD). Our aim is to investigate the association between the iPF level and occurrence of ILD in RA and the correlation of iPF with disease activity in general or only in RA with ILD.

METHODS

The study included 50 RA patients without ILD, 33 RA patients with ILD, and 30 healthy controls. Demographic data, Disease Activity Score 28 (DAS28), autoantibodies, and iPF were evaluated. ILD was diagnosed by using high-resolution computed tomography with clinical findings and chest X-ray. The samples were analyzed for complete blood count with platelet indices included, on Mindray BC-6800 hematology analyzer, Hamburg, Germany.

RESULTS

iPF levels were higher in RA patients with ILD compared to healthy controls and RA patients without ILD. A weakly positive correlation between DAS28 with iPF was found in all RA patients. iPF levels were found as 2.85 to detect ILD with 66.7% sensitivity and 65% specificity.

CONCLUSIONS

Our results showed that the iPF was detected higher in RA with ILD compared to RA without ILD. iPF, a routine cheap and easy test during hemogram, can provide important information in terms of disease activity and lung involvement in RA.

Immature Platelet Fraction in Rheumatoid Arthritis with Interstitial Lung Disease

BACKGROUND

Platelets have an effect on the hemostatic defense of the lung. Immature platelet fractions (iPF) reflects the number of young platelets containing ribonucleic acid in the circulation and real-time production. Information about their roles in rheumatic diseases is limited and there are no studies on iPF in RA with interstitial lung disease (ILD). Our aim is to investigate the association between the iPF level and occurrence of ILD in RA and the correlation of iPF with disease activity in general or only in RA with ILD.

METHODS

The study included 50 RA patients without ILD, 33 RA patients with ILD, and 30 healthy controls. Demographic data, Disease Activity Score 28 (DAS28), autoantibodies, and iPF were evaluated. ILD was diagnosed by using high-resolution computed tomography with clinical findings and chest X-ray. The samples were analyzed for complete blood count with platelet indices included, on Mindray BC-6800 hematology analyzer, Hamburg, Germany.

RESULTS

iPF levels were higher in RA patients with ILD compared to healthy controls and RA patients without ILD. A weakly positive correlation between DAS28 with iPF was found in all RA patients. iPF levels were found as 2.85 to detect ILD with 66.7% sensitivity and 65% specificity.

CONCLUSIONS

Our results showed that the iPF was detected higher in RA with ILD compared to RA without ILD. iPF, a routine cheap and easy test during hemogram, can provide important information in terms of disease activity and lung involvement in RA.

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.

Usefulness of Measurement of Reticulated Platelets for Diagnosis of Idiopathic Thrombocytopenic Purpura

Reticulated platelets (RP) and large platelets (LP) were measured by an automated hematology analyzer (modified R-2000) in 287 healthy volunteers and 131 patients with thrombocytopenia or thrombocytosis. RP was significantly higher in patients with idiopathic thrombocytopenic purpura (ITP), especially in active phase, while RP was markedly lower in patients with essential thrombocytosis (ET) or chronic myelocytic leukemia (CML). LP was significantly higher in patients with ITP, especially in active phase, while LP was markedly lower in patients with aplastic anemia (AA), ET, or CML. In ITP, RP and LP were significantly higher in patients positive for anti-glycoprotein (Gp) IIb/IIIa antibody. RP and LP were poorly correlated with platelet-associated IgG (PAIgG). RP and LP were poorly correlated with plasma thrombopoietin levels, and negatively correlated with platelet count. These results show that RP reflects the pathology of thrombocytopenic disorders, and that measurement of RP is useful for the differential diagnosis and analysis of platelet kinetics.

Usefulness of Fully Automated Measurement of Reticulated Platelets Using Whole Blood

Reticulated platelets (RP) were measured with an automated hematology analyzer (modified R-2000) in 287 healthy volunteers and in 212 patients with thrombocytopenia. In healthy volunteers, the RP was 0.48 ± 0.26% in men and 0.48 ± 0.32% in women. No significant difference in the RP values due to gender or age (21-60 years) was observed. Furthermore, the reverse correlation was observed between platelet counts and RP. The RP was high in patients with idiopathic thrombocytopenic purpura (ITP), those with high fibrinogen and fibrin degradation products (FDP), and those with high C-reactive protein (CRP), but low in patients after chemotherapy. The RP was highest in active phase of ITP, and relatively high in the partial remission phase of aplastic anemia. In patients after chemotherapy, the patients had a minimum phase of RP and then a maximum phase of RP before platelet counts increased. RP was significantly high in the maximum phase and significantly low in the minimum phase. The relationships between platelet count and RP were negatively correlated in patients with ITP, high FDP, or high CRP, but were not correlated in patients with aplastic anemia, liver disease, or after chemotherapy. These results show that RP reflects the pathology of thrombocytopenic disorders and the measurement of RP is useful for the differential diagnoses and analysis of platelet kinetics.

Impact of Atrial Fibrillation and Sinus Rhythm Restoration on Reticulated Platelets

OBJECTIVE

To assess the impact of nonvalvular atrial fibrillation (NVAF) and sinus rhythm restoration on the distribution of reticulated platelets (RPs), which are known to be associated with thrombotic propensity and have a greater predilection for thrombus participation.

PARTICIPANTS AND METHODS

The RP content was assessed by flow cytometry (thiazole orange/CD61) in 110 consecutive patients with NVAF before and 3 to 4 months after catheter ablation of the pulmonary veins. Results were compared with those of 55 age- and sex-matched controls with normal sinus rhythm.

RESULTS

The mean ± SD percentage of RPs was higher in patients with NVAF compared with controls (28.5%±7.3% vs 6.4%±5.3%; P<.001). The RP content did not vary by CHA2DS2-VASc score. After catheter ablation of the pulmonary veins, 63 patients were available for follow-up assessment. A significant reduction of RPs was observed compared with preintervention values (29.85%±7.1% vs 20.79%±7.6%; P<.001). During follow-up, 19% of patients (12 of 63) had confirmed AF recurrence. The mean ± SD percentage of RPs was higher in this group than in those without a recurrence (24.7%±6.5% vs 18.9%±7.5%; P=.01).

CONCLUSION

Nonvalvular atrial fibrillation affects the percentage of RPs, independent of the CHA2DS2-VASc score. After ablation, RP content dropped significantly. High RP content in patients with NVAF may explain the potential mechanism of thromboembolic complications and the lack of efficacy of currently available antiplatelet therapy for stroke prevention in this dysrhythmia.

Comparative analysis of human ex vivo-generated platelets vs megakaryocyte-generated platelets in mice: a cautionary tale

Thrombopoiesis is the process by which megakaryocytes release platelets that circulate as uniform small, disc-shaped anucleate cytoplasmic fragments with critical roles in hemostasis and related biology. The exact mechanism of thrombopoiesis and the maturation pathways of platelets released into the circulation remain incompletely understood. We showed that ex vivo-generated murine megakaryocytes infused into mice release platelets within the pulmonary vasculature. Here we now show that infused human megakaryocytes also release platelets within the lungs of recipient mice. In addition, we observed a population of platelet-like particles (PLPs) in the infusate, which include platelets released during ex vivo growth conditions. By comparing these 2 platelet populations to human donor platelets, we found marked differences: platelets derived from infused megakaryocytes closely resembled infused donor platelets in morphology, size, and function. On the other hand, the PLP was a mixture of nonplatelet cellular fragments and nonuniform-sized, preactivated platelets mostly lacking surface CD42b that were rapidly cleared by macrophages. These data raise a cautionary note for the clinical use of human platelets released under standard ex vivo conditions. In contrast, human platelets released by intrapulmonary-entrapped megakaryocytes appear more physiologic in nature and nearly comparable to donor platelets for clinical application.

Pak2 restrains endomitosis during megakaryopoiesis and alters cytoskeleton organization

Megakaryocyte maturation and polyploidization are critical for platelet production; abnormalities in these processes are associated with myeloproliferative disorders, including thrombocytopenia. Megakaryocyte maturation signals through cascades that involve p21-activated kinase (Pak) function; however, the specific role for Pak kinases in megakaryocyte biology remains elusive. Here, we identify Pak2 as an essential effector of megakaryocyte maturation, polyploidization, and proplatelet formation. Genetic deletion of Pak2 in murine bone marrow is associated with macrothrombocytopenia, altered megakaryocyte ultrastructure, increased bone marrow megakaryocyte precursors, and an elevation of mature CD41(+) megakaryocytes, as well as an increased number of polyploid cells. In Pak2(-/-) mice, platelet clearance rate was increased, as was production of newly synthesized, reticulated platelets. In vitro, Pak2(-/-) megakaryocytes demonstrate increased polyploidization associated with alterations in β1-tubulin expression and organization, decreased proplatelet extensions, and reduced phosphorylation of the endomitosis regulators LIM domain kinase 1, cofilin, and Aurora A/B/C. Together, these data establish a novel role for Pak2 as an important regulator of megakaryopoiesis, polyploidization, and cytoskeletal dynamics in developing megakaryocytes.

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.

The American Society of Hematology 2011 evidence-based practice guideline for immune thrombocytopenia

Immune thrombocytopenia (ITP) is commonly encountered in clinical practice. In 1996 the American Society of Hematology published a landmark guidance paper designed to assist clinicians in the management of this disorder. Since 1996 there have been numerous advances in the management of both adult and pediatric ITP. These changes mandated an update in the guidelines. This guideline uses a rigorous, evidence-based approach to the location, interpretation, and presentation of the available evidence. We have endeavored to identify, abstract, and present all available methodologically rigorous data informing the treatment of ITP. We provide evidence-based treatment recommendations using the GRADE system in those areas in which such evidence exists. We do not provide evidence in those areas in which evidence is lacking, or is of lower quality--interested readers are referred to a number of recent, consensus-based recommendations for expert opinion in these clinical areas. Our review identified the need for additional studies in many key areas of the therapy of ITP such as comparative studies of "front-line" therapy for ITP, the management of serious bleeding in patients with ITP, and studies that will provide guidance about which therapy should be used as salvage therapy for patients after failure of a first-line intervention.

Aberrant increase in the immature platelet fraction in patients with myelodysplastic syndrome: a marker of karyotypic abnormalities associated with poor prognosis

OBJECTIVES

Some patients with myelodysplastic syndrome (MDS) show a marked increase in the percentage of immature platelet fraction (IPF%) despite the absence of severe thrombocytopenia. To determine the significance of such an unbalanced increase in the IPF%, we investigated the IPF% and other laboratory findings of 51 patients recently diagnosed with MDS.

METHOD

Subjects consisted of 80 healthy males, 90 healthy females, and 51 patients with MDS and 20 patients with idiopathic thrombocytopenic purpura (ITP). The IPF and IPF% were determined using a Sysmex XE-2100 system loaded with IPF Master software (XE IPF Master, Sysmex). Platelet counts were measured simultaneously.

RESULTS

IPF% and platelet counts of these patients ranged from 1.1% to 25.1% (median, 5.3%) and from 6 to 260 x 10(9)/L (median, 71 x 10(9)/L), respectively. Twelve patients showed platelet counts more than 50 x 10(9)/L with 10% or more IPF%. All of the 12 patients had chromosome abnormalities including monosomy 7 and complex abnormalities involving 7 or 5q. In the other 39 patients who did not show the aberrant IPF% increase, chromosomal abnormalities were seen only in seven patients and none of them had chromosome 7 abnormalities. The IPF% of two patients increased to more than 10% in association with the appearance of monosomy 7.

CONCLUSIONS

These findings suggest that a high IPF% in MDS patient may be a marker for karyotypic abnormalities with a poor prognosis, including chromosome 7 abnormalities.

Reticulated platelet counts correlate with treatment response in patients with idiopathic thrombocytopenic purpura and help identify the complex causes of thrombocytopenia in patients after allogeneic hematopoietic stem cell transplantation

BACKGROUND

In thrombocytopenic conditions of unknown origin, quantification of reticulated platelets (RP) in the peripheral blood by flow cytometry has been shown to differentiate increased platelet (Plt) turnover from insufficient Plt production.

METHODS

We used a whole blood flow cytometry method combining thiazole orange and anti-CD41a-staining to assess RP in 71 healthy subjects, six with thrombocytopenic myelodysplastic syndrome (MDS), nine with liver cirrhosis, 14 patients with idiopathic thrombocytopenic purpura (ITP), and 12 patients who had undergone hematopoietic stem cell transplantation (HSCT).

RESULTS

Patients with MDS had normal, patients with liver cirrhosis had slightly elevated RP counts compared to healthy subjects. ITP patients had elevated RP counts, and RP >15% were associated with treatment response (P = 0.015). In 7/10 patients after HSCT, an increase of RP preceded Plt recovery, whereas in patients with secondary thrombocytopenia after normal regeneration, the assessment of RP allowed the differentiation between conditions with high Plt turnover, such as GvHD and microangiopathy, indicated by high RP counts, and graft failure, indicated by low RP counts.

CONCLUSIONS

Our data provide the rationale for prospective studies on the diagnostic and prognostic value of RP counts in larger patient populations with ITP and after HSCT.

Immature platelet fraction for prediction of platelet engraftment after allogeneic stem cell transplantation

Platelet regeneration represents an important and separate element in the engraftment process for allogeneic stem cell transplantation. Fully automated flow cytometry using blood cell counters now allows reliable quantification of reticulated platelets, expressed as the immature platelet fraction (IPF). We studied the kinetics of IPF in six patients grafted with allogeneic peripheral blood stem cell transplantation (PBSCT), 12 patients with bone marrow transplantation (BMT) and seven patients with cord blood transplantation (CBT). Preconditioning therapy caused an immediate and rapid fall in tri-lineage hematopoiesis. IPF rose transiently above 3% after a mean duration of 11 days post-PBSCT, 18 days post-BMT and 19 days post-CBT. This was 1, 4 and 13 days earlier than platelet engraftment, respectively. A linear correlation model showed a close association between the rise of IPF and tri-lineage engraftment after transplantation. IPF counting may thus provide an accessible measure of thrombopoietic activity, leading to early evaluation of marrow function and allowing monitoring of platelet regeneration.

A simple technique to determine thrombopoiesis level using immature platelet fraction (IPF)

Immature platelet fraction (IPF) has been measured by fully automated analyzer (XE-2100) as reticulated platelet (RP) which is reflected with thrombopoiesis in bone marrow. IPF value in the healthy volunteers was 3.3% (1.0-10.3) and upper 95% confidential interval (95% CI) of IPF was determined as 7.7%. IPF was significantly high in the patients with idiopathic thrombocytopenic purpura (ITP; 17.4%, 1.2-53.2%) and recovery phase of post-chemotherapy, and significantly low in nadir phase of post-chemotherapy, and within normal range in the patients with ITP in complete remission (CR) and with aplastic anemia (AA). Total count of IPF was significantly low in patients with ITP, AA or post-chemotherapy. Mean platelet volume (MPV) was significantly high in only patients with ITP. IPF 7.7% is best point for highest sensitivity (86.8%) and specificity (92.6%) in diagnosis of ITP and recovery phase of post-chemotherapy. In receiver operating characteristic curve for diagnosis of ITP and recovery phase of post-chemotherapy, IPF was significantly more useful than MPV. These results show that IPF reflects the pathology of thrombocytopenic disorders, and that measurement of IPF is useful for the differential diagnosis and analysis of platelet kinetics.

Chronic thrombocytopenia of childhood: use of non-invasive methods in clinical evaluation

OBJECTIVES

An unselected group of 21 children with chronic thrombocytopenia was investigated to understand the patients' platelet abnormality better.

METHODS

Platelet counts, mean platelet volumes (MPV), membrane glycoproteins and Fcgamma receptor type IIA (FcgammaRIIA) polymorphism H131R, reticulated platelets (% RP), antiplatelet antibodies and plasma thrombopoietin (TPO) were measured.

RESULTS

Sixteen patients had idiopathic thrombocytopenic purpura (ITP) (group 1: platelets < 50 x 10(9)/L, n = 6; group 2: 50-99 x 10(9)/L, n = 4; group 3: 100-149 x 10(9)/L, n = 4; group 4: splenectomised patients with normal platelet counts, n = 2). Five patients had familial thrombocytopenia. Six healthy children were studied as a reference. In the 19 thrombocytopenic patients, the platelets were significantly larger and % RP and TPO levels were significantly higher than those in the controls. Increased megakaryocytosis at diagnosis was associated with larger MPV and higher % RP but not with platelet level or TPO. The % RP was remarkably high in all ITP patients of group 1 indicating a brisk production of platelets despite low peripheral count. In all patients with familial thrombocytopenia, TPO was increased suggesting that the syndrome was not because of defective TPO production. The distribution of FcgammaRIIA alleles in the patients was similar to that in the controls.

CONCLUSIONS

A combined application of % RP and TPO could be helpful in classifying patients with chronic thrombocytopenia into different categories. The observations may be of value in the clinical evaluation of ITP patients and lead to avoidance of invasive examinations at least in some patients.

Immune thrombocytopenic purpura

Although many advances have been achieved in the understanding of ITP, critical issues regarding the pathophysiology and biology of the disease remain to be elucidated. The recent characterization of the human genome along with new sophisticated molecular biology techniques will allow basic researchers to study genes that may affect the presentation and clinical course of the disease. Different patterns of gene expression in this population can be studied, leading to the identification of subsets of patients with ITP at higher risk of bleeding. The multigene patterns of expression might also provide clues about regulatory mechanisms and broader cellular functions. In order to answer essential clinical questions, like the incidence of ICH in relation to drug treatment or observation alone, clinical trials should be appropriately designed. More studies are necessary to better define the optimal treatment approach for each child with ITP. Even though the incidence of intracranial hemorrhage cannot be used as the primary outcome measure because of its rarity, numerous other outcomes, such as rate of rise in platelet count, cost and side effects of therapy, health related quality of life of the patient and family, and severity of hemorrhage can be measured and compared between treatment groups. Future investigators should find it attractive to conduct trials in children with this common hematological disease so that decision making can be based more on scientific evidence than on anecdote and opinion.

Automated image processing. Past, present, and future of blood cell morphology identification

Automated image processing analysis for leukocyte differential counting started 30 years ago principally as a mimic of the traditional microscopic method. Several types of systems were used in the 1970s and 1980s. In the late 1990s, two new image processing systems were developed with new technology for cell image analysis. They possess an intelligent neural network software and can be connected to an Ethernet for telehematologic diagnosis and consultation.