Diagnostic value of tests for reticulated platelets, plasma glycocalicin, and thrombopoietin levels for discriminating between hyperdestructive and hypoplastic thrombocytopenia

Shedding light on GPIbα shedding

PURPOSE OF REVIEW

Ectodomain shedding has been investigated since the late 1980s. The abundant and platelet specific GPIbα receptor is cleaved by ADAM17 resulting in the release of its ectodomain called glycocalicin. This review will address the role of glycocalicin as an end-stage marker of platelet turnover and storage lesion and will consider a potential function as effector in processes beyond hemostasis.

RECENT FINDINGS

Glycocalicin has been described as a marker for platelet senescence, turnover and storage lesion but is not routinely used in a clinical setting because its diagnostic value is nondiscriminatory. Inhibition of glycocalicin shedding improves posttransfusion recovery but little is known (yet) about potential hemostatic improvements. In physiological settings, GPIbα shedding is restricted to the intracellular GPIbα receptor subpopulation suggesting a role for shedding or glycocalicin beyond hemostasis.

SUMMARY

So far, all evidence represents glycocalicin as an end-stage biomarker of platelet senescence and a potential trigger for platelet clearance. The extensive list of interaction partners of GPIbα in fields beyond hemostasis opens new possibilities to investigate specific effector functions of glycocalicin.

Immature platelet dynamics are associated with clinical outcomes after major trauma

BACKGROUND

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSION

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

Translating mechanisms into therapeutic strategies for immune thrombocytopenia (ITP): Lessons from clinical trials

Immune thrombocytopenia (ITP) is an autoimmune disorder that causes a significant reduction in peripheral blood platelet count. Fortunately, due to an increased understanding of ITP, there have been significant improvements in the diagnosis and treatment of these patients. Over the past decade, there have been a variety of proven therapeutic options available for ITP patients, including intravenous immunoglobulins (IVIG), Rituximab, corticosteroids, and thrombopoietin receptor agonists (TPO-RAs). Although the effectiveness of current therapies in treating more than two-thirds of patients, still some patients do not respond well to conventional therapies or fail to achieve long-term remission. Recently, a significant advancement has been made in identifying various mechanisms involved in the pathogenesis of ITP, leading to the development of novel treatments targeting these pathways. It seems that new agents that target plasma cells, Bruton tyrosine kinase, FcRn, platelet desialylation, splenic tyrosine kinase, and classical complement pathways are opening new ways to treat ITP. In this study, we reviewed the pathophysiology of ITP and summarized updates in this population's management and treatment options. We also took a closer look at the 315 ongoing trials to investigate their progress status and compare the effectiveness of interventions. May our comprehensive view of ongoing clinical trials serve as a guiding beacon, illuminating the path towards future trials of different drugs in the treatment of ITP patients.

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.

Hereditary thrombocytopenia with platelet sialic acid deficiency and mutations in the GNE genes

BACKGROUND

The inherited macrothrombocytopenias are rare disorders and the underlying cause can be identified in many cases but in some, this can remain enigmatic. Platelet transfusions are often administered during hemorrhagic events.

METHODS

A patient with previously unexplained inherited macrothrombocytopenia with a platelet count between 3-20 × 10⁹ /L is described in which studies were performed using exome sequencing (ES) and platelet flow cytometry.

RESULTS

Both the hemoglobin and white cell counts were normal. ES revealed two suspicious variants, one likely pathogenic and one a variant of uncertain significance, in the UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE) gene, and flow cytometry showed diminished expression of surface platelet sialic acid (about 5%) but normal red cell sialic acid. The Thrombopoietin (TPO) level was low, and the patient responded to TPO-mimetic treatment with an increase in the platelet count.

CONCLUSION

Two variants in the GNE gene were able to be upgraded to pathogenic with apparently restricted expression to the megakaryocyte lineage. Platelet transfusion may be avoided in these patients with TPO-mimetic treatment.

Evaluation of a novel moving threshold gating strategy for assessment of reticulated platelets in dogs using the ADVIA 2120 analyzer

BACKGROUND

A novel method using a moving threshold (r-PLTmt) to determine canine r-PLTs (reticulated platelets) has been introduced for ADVIA 2120 software v6.11.7.

OBJECTIVES

We aimed to evaluate absolute (ar-PLTmt) and percent (%r-PLTmt) prior to and after visual inspection of scattergrams (ar-PLTmtv, %rPLTmtv) compared with flow cytometry (flow) and to determine reference intervals (RIs) in 120 dogs.

METHODS

For method comparison, 42 blood samples of healthy and thrombocytopenic dogs were included. Calculation of Spearman's rho, Bland-Altman, and Passing-Bablok analysis was performed. Coefficients of variation (CVs) were determined for three concentration levels.

RESULTS

Moderate correlations between %r-PLTmt and %r-PLTmtv (r_s 0.75-0.76) were seen compared with flow cytometry. The CV for medium %r-PLTs counts assessed with flow cytometry was 12.9%. Comparable CVs were obtained for ar-PLTmt (14.4%) and %r-PLTmt (15.7%), and ar-PLTmtv and %r-PLTmtv (10.9% and 12.9%, respectively). At low and high concentration levels, CVs for % and absolute r-PLTmt/rPLTmtv ranged between 23%-30% and 15%-20%. In patients with microcytic hypochromic erythrocytes, CVs for ar-PLTmt and %r-PLTmt were 36%-66%. Visual inspection of scattergrams resulted in a marked decrease in CV ranging between 15% and 20%. A proportional bias of 10.8% between %r-PLTmt and flow cytometry became lower (9.7%) after visual validation of scattergrams. Passing-Bablok analysis showed proportional and constant error. RIs for r-PLTmt and r-PLTmtv were 0.2%-3.8% and 0.6-10.2 × 10⁹ /L and 0.3%-4.5% and 1.1-10.3 × 10⁹ /L, respectively. Median values for %r-PLTmtv were higher in young adults (≤2 years) than in older dogs (P = 0.03).

CONCLUSIONS

r-PLTmt and r-PLTmtv were moderately correlated with flow cytometry. Visual inspection of scattergrams is recommended.

Novel Biomarkers for Diagnosis and Monitoring of Immune Thrombocytopenia

Lower-than-normal platelet counts are a hallmark of the acquired autoimmune illness known as immune thrombocytopenia, which can affect both adults and children. Immune thrombocytopenia patients' care has evolved significantly in recent years, but the disease's diagnosis has not, and it is still only clinically achievable with the elimination of other causes of thrombocytopenia. The lack of a valid biomarker or gold-standard diagnostic test, despite ongoing efforts to find one, adds to the high rate of disease misdiagnosis. However, in recent years, several studies have helped to elucidate a number of features of the disease's etiology, highlighting how the platelet loss is not only caused by an increase in peripheral platelet destruction but also involves a number of humoral and cellular immune system effectors. This made it possible to identify the role of immune-activating substances such cytokines and chemokines, complement, non-coding genetic material, the microbiome, and gene mutations. Furthermore, platelet and megakaryocyte immaturity indices have been emphasized as new disease markers, and prognostic signs and responses to particular types of therapy have been suggested. Our review's goal was to compile information from the literature on novel immune thrombocytopenia biomarkers, markers that will help us improve the management of these patients.

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).

Analysis of predictors after partial splenic embolization for thrombocytopenia with liver cirrhosis

Blood transfusion, splenectomy, and partial splenic embolization (PSE) are generally performed for thrombocytopenia in patients with cirrhosis. Recently, thrombopoietin (TPO) agonists have become available, and investigations of patients who would benefit from them are necessary. Therefore, it is important to understand the fluctuations in cytokine levels associated with PSE. Therefore, fluctuations in platelet-associated immunoglobulin G (PAIgG), interleukin 6 (IL-6), and TPO levels with PSE were analyzed in this study. The study included 110 patients with liver cirrhosis and thrombocytopenia, with the aim of improving platelet counts. Fluctuations in PAIgG, IL-6, and TPO levels were investigated. The average splenic embolization ratio was 58.0% in patients with PSE. The platelet count rose significantly from 6.95 [5.40, 8.60] × 104/mL to 14.05 [10.43, 18.05] × 104/mL (P < .01), IL-6 rose significantly from 3.56 [2.53, 7.33] pg/mL to 18.90 [9.17, 32.95] pg/mL (P < .01), TPO rose significantly from 0.82 [0.52, 1.21] fmol/mL to 1.58 [0.97, 2.26] fmol/mL (P < .01), and PAIgG decreased significantly from 64.20 [38.33, 118.75] ng/107 cells to 37.50 [22.25, 70.00] ng/107 cells (P < .01). On multivariate analysis of factors related to the rate of platelet increase with PSE, primary biliary cholangitis (B = 0.475, P < .01), splenic embolization ratio (B = 0.75, P < .01), IL-6 change ratio (B = 0.019, P < .01), and PAIgG change ratio (B = -0.325, P < .01) were significant. When attempting to improve thrombocytopenia with PSE, adequate splenic embolization needs to be obtained together with improvements in IL-6, PAIgG, and TPO levels. With unsatisfactory improvement in thrombocytopenia, TPO agonist administration was considered.

Changing profile of platelet activity and turnover indices during treatment response of immune thrombocytopenia

Both platelet count and function change after treatment of immune thrombocytopenia. Platelet function can be measured by plasma markers, including platelet activity [e.g., soluble P-selectin (sP-selectin) and soluble CD40 ligand (sCD40L)] and platelet turnover markers [e.g., glycocalicin (GC)]. Patients were classified into no response (NR, including new diagnosis), partial response (PR) and complete response (CR). One hundred and sixteen samples (29 CR, 32 PR, 55 NR) from 79 patients were collected. Plasma markers (sP-selectin, sCD40L and GC) were measured by ELISA. Platelet counts and mean platelet volume (MPV) were obtained in the clinical laboratory using GenS System-2. The results showed that responsive patients (PR + CR) had higher levels of sP-selectin (P = 0.026) and sCD40L (P = 0.001). Although there was no difference in MPV (P = 0.077) or GC (P = 0.078), there was a marked decrease of GC index (P < 0.001) in responsive patients. Paired sample analysis showed no difference in sP-selectin, sCD40L, MPV or GC but significant difference in GC index (P = 0.017) between NR and PR. Another paired sample analysis showed no difference in sP-selectin, sCD40L, MPV or GC but significant difference in GC index (P = 0.029) between PR and CR. Patients with refractory and newly diagnosed disease had a significant difference in GC (P = 0.020) and sCD40L (P = 0.001), despite similarly low platelet counts. In conclusion, platelet activity markers (sP-selectin and sCD40L) and GC indices change in parallel with treatment response. Plasma levels of GC and sCD40L may be predictors of treatment response.

Development of an Automated Chemiluminescent Enzyme Immunoassay for Measuring Thrombopoietin in Human Plasma

Plasma thrombopoietin (TPO) measurements help distinguish between different types of thrombocytopenia but are not feasible in routine clinical practice. We developed a fully automated quantitative chemiluminescent enzyme immunoassay (CLEIA) for measuring TPO (TPO-CLEIA), which is a one-step sandwich-type assay. This assay utilizes a mouse monoclonal capture antibody, which has the neutralizing epitope of the interaction between TPO and the TPO receptor, and a newly generated rabbit monoclonal detector antibody. In analytical performance studies, this assay showed good linearity over the measuring range and high sensitivity. The limit of quantification (LoQ) of this assay was 3.4 pg/mL; low TPO concentration values of almost all healthy individuals exceeded the LoQ value. In clinical validation studies, TPO levels obtained from patients with aplastic anemia (AA) significantly increased, whereas those of patients with immune thrombocytopenia (ITP) were normal or slightly increased. The cutoff value for TPO-CLEIA corresponding to the previously reported values was useful for distinguishing between ITP and AA. These results suggest that TPO-CLEIA can quantify human plasma TPO levels with high accuracy and sensitivity and has the potential to facilitate routine clinical measurement of TPO in patients with various types of thrombocytopenia.

Autoimmune-mediated thrombocytopenia after allogeneic hematopoietic stem cell transplantation: significance of detecting reticulated platelets and glycoprotein-specific platelet autoantibodies

Autoimmune hematological disorders are rare complications after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Diagnosis of immune thrombocytopenia (ITP) is challenging, especially after allo-HSCT, because various complications such as graft-versus-host disease, disease relapse, viral infection, thrombotic microangiopathy, and drug side effects can also cause thrombocytopenia. Assessment of reticulated platelets (RP) and plasma thrombopoietin (TPO) levels may be useful to distinguish between ITP and hypoplastic thrombocytopenia. ITP is generally characterized by an increased percentage of RP, and a normal or slightly increased plasma TPO level. We now report three cases of thrombocytopenia after allo-HSCT. RP% was elevated in these patients, as it is in primary ITP. However, in contrast to primary ITP, plasma TPO levels were high in two of three patients. Anti-αIIbβ3 and anti-GPIb/IX-specific direct IgG antibodies were detected as well, suggesting occurrence of immune-mediated platelet destruction in addition to bone marrow suppression in two patients. All three patients were successfully treated with corticosteroids and/or thrombopoietin receptor agonists (TPO-RAs). These results suggest that increased RP% and detection of glycoprotein-specific platelet autoantibodies are useful for the diagnosis of ITP after HSCT.

Immature Platelet Dynamics in Immune-Mediated Thrombocytopenic States

A major challenge encountered by clinicians is differentiating presentations characterized by significant thrombocytopenia due to overlapping clinical symptoms and signs in the setting of ambiguous laboratory results. Immature platelets represent the youngest platelets that can be measured in peripheral blood by current hematology analyzers. These young platelets are larger, with higher RNA content recently released from the bone marrow. Thrombocytopenic presentations caused directly or indirectly by immune responses can lead to compensatory bone marrow responses seeking to normalize the platelet count; thus obtaining absolute immature platelet counts may be informative while triaging patients. Over the last decade, their use has expanded beyond being an early biomarker of bone marrow reconstitution post-hematopoietic stem cell transplantation to being used to establish bone marrow responses to infection and thrombocytopenias due to immune etiologies. Its accessibility as part of more detailed platelet indices obtained with routine laboratories makes it a promising option to understand the bone marrow's real-time response to disease states characterized by thrombocytopenia. This review will look at the immature platelet count as a biomarker, while presenting current attempts trying to understand how it could be used in thrombocytopenias occurring secondary to a given immune etiology.

Association between Platelet-Associated Immunoglobulin G Levels and Response to Corticosteroid Therapy in Patients with Newly Diagnosed Immune Thrombocytopenia

OBJECTIVE

Platelet-associated immunoglobulin G (PA-IgG) refers to IgG attached to the surface of platelets, while the immature platelet fraction (IPF) reflects the state of platelet production in bone marrow. Since PA-IgG and IPF are increased in patients with immune thrombocytopenia (ITP), reflecting amounts of platelet antibodies and compensatory platelet production, respectively, we hypothesized that these laboratory findings may provide useful markers for predicting treatment response in patients with ITP. We therefore retrospectively investigated associations between levels of these markers at diagnosis and response to first-line therapy in patients with ITP.

METHODS

Forty-three patients diagnosed with ITP at Oita Kouseiren Tsurumi Hospital between May 2010 and November 2018 were included. Patients were divided into 2 groups based on response to corticosteroid as first-line therapy. Laboratory findings were compared between responders and nonresponders.

RESULTS

Median PA-IgG was 285 ng/107 cells (range, 45.5-18,200 ng/107 cells), and median IPF was 15.5% (range, 5.4-62.1%). Median levels were higher than the respective upper limits of normal range (PA-IgG, 0-46 ng/107 cells; IPF, 1.1-9.5%). First-line therapy was performed using standard-dose prednisolone (0.5-1.0 mg/kg/day) in 32 patients and high-dose dexamethasone (40 mg/day, 4 days) or methylprednisolone (125-1,000 mg/day, 3-4 days) in 11 patients. Twenty-four patients (55.8%) responded to first-line therapy. In univariate analysis, type of corticosteroid (p = 0.17) tended to differ between groups but did not differ significantly, and no difference in IPF level was apparent between responders (15.35%; range, 5.4-41.5%) and nonresponders (16.7%; range, 6.3-62.1%; p = 0.15). PA-IgG was significantly higher among nonresponders (430 ng/107 cells; range, 101-18,200 ng/107 cells) than among responders (254.5 ng/107 cells; range, 45.5-470 ng/107 cells; p = 0.004). Multivariate analysis revealed PA-IgG was independently associated with response to first-line therapy (odds ratio, 1.000; 95% confidence interval, 1.000-1.010; p = 0.029).

CONCLUSION

Our data suggested that PA-IgG at diagnosis could offer a useful predictor of response to first-line corticosteroid therapy for ITP.

Knock-in mice bearing constitutively active αIIb(R990W) mutation develop macrothrombocytopenia with severe platelet dysfunction

BACKGROUND

To date, several mutations that induce constitutive activation of integrin αIIbβ3 have been identified in congenital macrothrombocytopenia. Of these, αIIb(R995W) is the most prevalent mutation observed in Japanese patients with αIIbβ3-related congenital macrothrombocytopenia.

OBJECTIVE AND METHODS

The present study aimed to explore the effects of constitutive activation of the αIIb(R995W) mutation on platelet production, morphology, and function. We generated αIIb(R990W) knock-in (KI) mice corresponding to human αIIb(R995W).

RESULTS

Platelet counts of heterozygous (hetero) and homozygous (homo) KI mice were decreased by ~10% and ~25% relative to those of wild-type (WT) mice, respectively, with increase in platelet size. Decrease in absolute reticulated platelet numbers in steady state, delayed recovery from thrombocytopenia induced by anti-platelet antibody and impaired response to exogenous thrombopoietin administration suggested impaired platelet production in KI mice. WT and KI mice showed no significant differences in the number of megakaryocytes and ploidy of megakaryocytes, whereas proplatelet formation was significantly impaired in homo mice. We observed a slight but significant reduction in platelet lifespan in homo mice. The homo mice showed dramatic reduction in αIIbβ3 expression in platelets, which was accompanied by severe in vivo and in vitro platelet dysfunction.

CONCLUSION

The αIIb(R990W) KI mice developed macrothrombocytopenia, which was primarily attributed to impaired proplatelet formation. In addition, homo KI mice showed marked downregulation in αIIbβ3 expression in platelets with severe impaired platelet function, similar to Glanzmann thrombasthenia.

How do we diagnose immune thrombocytopenia in 2018?

In this report, we will review the various clinical and laboratory approaches to diagnosing immune thrombocytopenia (ITP), with a focus on its laboratory diagnosis. We will also summarize the results from a number of laboratories that have applied techniques to detect anti-platelet autoantibodies as diagnostic tests for ITP. Although there is considerable variability in methods among laboratories, there is general agreement that platelet autoantibody testing has a high specificity but low sensitivity. This suggests several possibilities: (1) the ideal test for ITP has yet to be developed, (2) current test methods need to be improved, or (3) ITP is the clinical expression of a variety of thrombocytopenic disorders with different underlying mechanisms. Even the clinical diagnosis of ITP is complex, and experienced clinicians do not always agree on whether a particular patient has ITP. Improvements in the diagnostic approach to ITP are necessary to improve the management of this disorder.

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.

Evaluation of bone marrow function with immature platelet fraction in normal pregnancy

BACKGROUND

Bone marrow function in pregnancy is influencing blood cell concentration of platelets. The steady state of consumption, recovery and production of platelets is essential for coagulation and bleeding prevention. Reticulated platelets are an intermediate form of thrombocytes during thrombopoiesis representing platelet production. The immature platelet fraction (IPF) represents these platelets as percentage of all thrombocytes. Until now, there is little knowledge on IPF during pregnancy.

MATERIAL AND METHODS

69 healthy pregnant women were included in this monocentric study. Serial blood samples of 27 women (study group 1) and single blood samples of 42 women (study group 2) were taken between 20 and 40weeks of gestation. IPF levels and thrombocytes were quantified by a routine clinical hematology analyzer. Both two study groups were analyzed separately.

RESULTS

IPF levels increased between 20 and 40weeks of gestation in both study groups. Median absolute values of IPF increased from 8.1/nl to 13.6/nl in study group 1 and remained constant in study group 2. Values in percent rose from 3.63% to 6.06% in study group 1 and from 4.9% to 6.01% in study group 2. Most values stayed below 20/nl or 7-7.5%. Highest IPF levels were measured near term. In contrast, thrombocyte counts decrease slightly during this period.

CONCLUSION

Bone marrow function is mirrored by IPF levels, which increase with gestational age in healthy pregnant women. Most IPF values remain below 20/nl or 7%. More studies are needed to improve understanding of thrombocyte turnover in pregnancy.

Impact of Mean Platelet Volume on Long-Term Mortality in Chinese Patients with ST-Elevation Myocardial Infarction

We investigated the association between mean platelet volume (MPV) and risk of all-cause mortality in Chinese patients with ST-Elevation Myocardial Infarction (STEMI). We enrolled 1836 patients with STEMI in Xuanwu Hospital from January 2008 to December 2013. Based on MPV, patients were categorized into the following groups: <9.5 fL (n = 85), 9.5–11.0 fL (n = 776), 11.1–12.5 fL (n = 811) and >12.5 fL (n = 164), respectively. Mean duration of follow-up was 56.9 months, and 197 patients (10.7%) died during follow-up. All-cause mortality rates were compared between groups. The lowest mortality occurred in patients with MPV between 9.5–11.0 fL, with a multivariable-adjusted hazard ratio (HR) of 1.15(95%CI 0.62–1.50), 1.38(95%CI 1.20–1.68), and 1.72(95%CI 1.41–1.96) in patients with MPV of <.5, 11.1–12.5 and >12.5 fL, respectively. Therefore, increased MPV was associated with all-cause mortality in Chinese patients with STEMI. MPV might be useful as a marker for risk stratification in Chinese patients with STEMI.

Red cell distribution width predicts totally occluded infarct-related artery in NSTEMI

Objective Since non-ST segment elevation myocardial infarction (NSTEMI) patients with totally occluded infarct-related artery (TO-IRA) have worse prognosis, it is important to recognize TO-IRA in NSTEMI. Red cell distribution width (RDW) and mean platelet volume (MPV) are novel markers of inflammation and oxidative stress and were associated with poor clinical outcomes in acute coronary syndrome. In the present study, association of RDW and MPV with the presence of TO-IRA in NSTEMI was investigated. Methods Data of 201 consecutive patients who underwent coronary angiography with a diagnosis of NSTEMI were analyzed. Independent predictors of TO-IRA were investigated with logistic regression analysis. Results Sixty-six (32.8%) of the patients had TO-IRA. In patients with TO-IRA, RDW and troponin-T were significantly higher and left ventricular ejection fraction (LVEF) was lower. MPV did not differ between groups. Circumflex (CX) IRA was more common in TO-IRA group. The ROC curve analysis showed that the RDW at a cut-point of 13.95% has 76% sensitivity and 66% specificity in detecting TO-IRA. RDW, troponin-T, LVEF and CX-IRA were independent predictors of TO-IRA in NSTEMI, but MPV was not. Conclusion RDW is a cheap and readily available marker that may have a role to predict TO-IRA in NSTEMI.

Purification of glycocalicin from human plasma

Glycocalicin (GC) is a large extracellular proteolytic fragment of glycoprotein Ib, a membrane platelet component playing an essential role in the physiological processes of platelet adhesion and aggregation. GC contains the binding sites for thrombin and von Willebrand factor. GC circulates normally in vivo in significant concentrations and the plasma level of this protein reflects a complex function of factors including platelet count or platelet turnover. It can therefore serve as a good indicator for many diseases like hypoplastic thrombocytopenia and idiopathic thrombocytopenic purpura. For this reason, several purification assays have been previously described. In this work, we describe a novel analytical method for GC purification from human platelets based on preparative HPLC gel filtration followed by immuno-affinity chromatography on NHS activated column conjugated with specific antibody. Pure GC was obtained from tiny amount of starting material. Our protocol of GC purification is simple, fast and provides a pure end product.

Analyses of Genetic and Clinical Parameters for Screening Patients With Inherited Thrombocytopenia with Small or Normal-Sized Platelets

BACKGROUND

Childhood thrombocytopenias include immune thrombocytopenic purpura (ITP) and inherited thrombocytopenia; the former is caused by autoantibodies to platelets, whereas the latter can be distinguished by platelet size and underlying genetic mutations. Due to limited methods for the definite diagnosis of ITP, genetic and clinical parameters are required for diagnosing inherited thrombocytopenias with small or normal-sized platelets.

PROCEDURE

In total, 32 Japanese patients with thrombocytopenia with small or normal-sized platelets from 29 families were enrolled. All the patients were under 20 years of age, with family histories of early-onset thrombocytopenia and/or poor response to conventional therapies for ITP. Genotypes and clinical parameters were retrospectively evaluated according to the disease type.

RESULTS

Twelve cases of inherited thrombocytopenia were observed. We identified chromosomal deletions within the WASP gene in two patients with Wiskott-Aldrich syndrome; a missense mutation in a patient with X-linked thrombocytopenia; and mutations in the RUNX1 gene of five patients with familial platelet disorder with propensity to acute myelogenous leukemia, and in the ANKRD26 gene of four patients with autosomal dominant thrombocytopenia-2. All 12 carried germline mutations, three of which were de novo. Furthermore, we observed significantly elevated serum thrombopoietin (TPO) levels and dysplasia of megakaryocytes in patients carrying the RUNX1 and ANKRD26 mutations.

CONCLUSIONS

Genetic analyses and detection of TPO levels and dysmegakaryopoiesis were clinically useful for screening patients with inherited thrombocytopenias, irrespective of the family history. We hypothesize that the WASP, RUNX1, and ANKRD26 genes are important for normal TPO signaling and the network underlying thrombopoiesis.

Mean platelet volume is a predictor of ST resolution following thrombolysis in acute ST elevation myocardial infarction

BACKGROUND

Larger mean platelets volumes (MPV) are thrombogenic and frequently seen after ST-segment elevation myocardial infarction (STEMI). This study aimed to examine the association of MPV and resolution of ST-segment after thrombolysis in STEMI patients as and its impact on clinical outcome.

METHODS

Patients presenting to the emergency department with the diagnosis of first STEMI and were referred to thrombolysis were screened. Patients with ≥50% ST-segment resolution (STR) 90minutes after thrombolysis were assigned as "Responder" and those with <50% STR were assigned as "Non-Responders". Demographic, clinical comorbidities and risk factor were recorded along with and angiographic data. In-hospital occurrence of major adverse cardiac events (MACE), including acute heart failure (AHF), reinfarction and death were investigated. Additionally, the patients were followed for 6 additional months after their discharge from the hospital.

RESULTS

STR≥50% was seen in 60.2% of patients after thrombolysis. Responders had significantly lower MPV (P=0.001) and the critical MPV values were 8.0 femtoliter (fL) and 8.2fL in predicting STR and MACE. Patients with MPV ≥8.2fL had lower probability of STR and higher rates of AHF (P<0.001), and MACE (P=0.001) compared to the patients with lower platelet volume. In multivariate regression, MPV was an independent predictor of STR (P<0.001) as well as MACE (HR=4.8, 95% CI of 1.8-12.4; P=0.001). Triple vessel disease was another independent factor that predicted MACE.

CONCLUSION

Higher MPV's at admission were associated with lower STR and higher occurrence of major adverse cardiac events in patients receiving thrombolytic therapy for first time STEMI.

Relationships of mean platelet volume and plasma thrombopoietin with glycocalicin levels in thrombocytopenic patients

BACKGROUNDS/AIMS

Relationships of mean platelet volume (MPV) and thrombopoietin (TPO) with platelet turnover assessed by glycocalicin measurement were evaluated in thrombocytopenic patients.

METHODS

MPV, glycocalicin and platelet-associated IgG (PA-IgG) were measured in 107 patients with idiopathic thrombocytopenic purpura (ITP) and 19 patients with hypoproductive thrombocytopenia (HPT; aplastic anemia or leukemia), and TPO was measured in 53 ITP and 12 HPT patients. All the included ITP patients had PA-IgG ≥300% and glycocalicin ≥50% of control values, and HPT patients had PA-IgG <300% and glycocalicin <50% of control values.

RESULTS AND CONCLUSIONS

MPV was higher in ITP than in HPT patients: 9.56 ± 1.69 and 7.59 ± 0.90 fl (p < 0.001). In the ITP group a direct correlation was detected between MPV and glycocalicin (r = 0.344, p < 0.001). This interaction was essentially expressed in patients with normal/increased glycocalicin (≥100% of control; r = 0.470, p < 0.001, n = 64). TPO was greatly enhanced in HPT in comparison with ITP patients (958 ± 659 and 11 ± 27 pg/ml, p < 0.001). In the ITP group a reverse correlation was detected between TPO and glycocalicin (r = -0.373, p = 0.006).

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.

Abnormal platelet kinetics are detected before the occurrence of thrombocytopaenia in HBV-related liver disease

BACKGROUND & AIMS

Thrombocytopaenia is a frequent feature in patients with HBV-related liver disease. Its underlying mechanism is not fully understood. Multiple factors might contribute to the development of thrombocytopaenia. In this study, we investigated the reticulated platelets (RP), glycocalicin (GC), serum thrombopoietin (TPO) and platelet glycoprotein (GP) in different stages of the disease.

METHODS

One hundred and fourteen patients with HBV-related liver disease (30 with chronic hepatitis B (CHB), 20 patients in Child A without thrombocytopaenia, 19 patients in Child A with thrombocytopaenia, 45 in Child B/C with thrombocytopaenia) and 25 normal controls (NC) were enrolled. Liver cirrhosis (LC) was classified according to modified Child-Turcotte-Pugh (CTP) score. Serum TPO levels and GC were measured by ELISA. RP and platelet glycoprotein (GP) expression were detected by flow cytometry.

RESULTS

The TPO levels of patients with LC were significantly lower than that of controls, even in patients of Child A without thrombocytopaenia group. Serum TPO level was positively correlated (r = 0.65, p < 0.01) with serum albumin in Child B/C group. Both the RP percentages and the glycocalicin index (GCI) levels were significantly higher in patients groups including CHB and Child A without thrombocytopaenia than that of normal controls. A negative correlation existed in HBV DNA copies and the GPs% in patients with CHB and Child A without thrombocytopaenia.

CONCLUSION

Abnormal platelet production, destruction and platelet-specific glycoproteins levels were detected before the occurrence of thrombocytopaenia in HBV-related liver disease, indicating that multiple mechanisms might play roles in thrombocytopaenia in HBV-infected patients.

Thrombocytopenia in patients with hepatitis B virus-related chronic hepatitis: evaluation of the immature platelet fraction

The immature platelet fraction (IPF) measures the number of reticulated platelets in peripheral blood, and can be used to help determine if thrombocytopenia is secondary to low-platelet production or increased platelet turnover. The aim of this study was to determine whether abnormalities in the IPF were associated with thrombocytopenia in patients with hepatitis B virus-related chronic hepatitis (CHB). One hundred fifty-six patients with chronic hepatitis B, including 80 thrombocytopenia, 76 without thrombocytopenia, and 48 healthy controls were enrolled in the study. The IPF percentages (IPF%) were measured using a XE-2100 multiparameter automatic hematology analyzer. We demonstrated that in the thrombocytopenic group, the IPF% was significantly increased compared with that in healthy controls and the non-thrombocytopenic group (both p < 0.001). Multivariate analysis demonstrated that IPF%, splenomegaly, and the model for end-stage liver disease score were independent predictors for thrombocytopenia (both p < 0.001). High IPF% during the course of thrombocytopenia suggests that platelet destruction/sequestration due to hypersplenism is a major factor contributing to thrombocytopenia in patients with CHB.

Platelet apoptosis and agonist-mediated activation in myelodysplastic syndromes

Patients with myelodysplastic syndromes (MDS) have a defect in the differentiation of bone marrow multipotent progenitor cells. Thrombocytopenia in MDS patients may be due to premature megakaryocyte death, but platelet apoptotic mechanisms may also occur. This study aimed to study function and apoptotic state of platelets from MDS patients with different platelet count. Reticulated platelets, platelet activation, activated caspases and annexin-V binding were evaluated by flow cytometry. Pro-apoptotic Bax and Bak proteins were determined by western blots and plasma thrombopoietin by ELISA. Microparticle-associated procoagulant activity and thrombin generation capacity of plasma were determined by an activity kit and calibrated automated thrombography, respectively. High plasma thrombopoietin levels and low immature circulating platelet count showed a pattern of hypoplastic thrombocytopenia in MDS patients. Platelets from MDS patients showed reduced activation capacity and more apoptosis signs than controls. Patients with the lowest platelet count showed less platelet activation and the highest extent of platelet apoptosis. On this basis, patients with thrombocytopenia should suffer more haemorrhagic episodes than is actually observed. Consequently, we tested whether there were some compensatory mechanisms to counteract their expected bleeding tendency. Microparticle-associated procoagulant activity was enhanced in MDS patients with thrombocytopenia, whereas their plasma thrombin generation capacity was similar to control group. This research shows a hypoplastic thrombocytopenia that platelets from MDS patients possess an impaired ability to be stimulated and more apoptosis markers than those from healthy controls, indicating that MDS is a stem cell disorder, and then, both number and function of progeny cells, might be affected.

How to approach thrombocytopenia

Thrombocytopenia is a common hematologic finding with variable clinical expression. A low platelet count may be the initial manifestation of infections such as HIV and hepatitis C virus or it may reflect the activity of life-threatening disorders such as the thrombotic microangiopathies. A correct identification of the causes of thrombocytopenia is crucial for the appropriate management of these patients. In this review, we present a systematic evaluation of adults with thrombocytopenia. The approach is clearly different between outpatients, who are frequently asymptomatic and in whom we can sometimes indulge in sophisticated and relatively lengthy investigations, and the dramatic presentation of acute thrombocytopenia in the emergency department or in the intensive care unit, which requires immediate intervention and for which only a few diagnostic tests are available. A brief discussion of the most common etiologies seen in both settings is provided.

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.

Thrombocytopenia is more severe in patients with advanced chronic hepatitis C than B with the same grade of liver stiffness and splenomegaly

BACKGROUND AND AIM

The mechanism responsible for thrombocytopenia in chronic liver diseases (CLD) is not yet fully understood. The prevalence of thrombocytopenia has been reported to be higher in patients with hepatitis C virus-related hepatocellular carcinoma (CLD-C) than in those with hepatitis B virus-related hepatocellular carcinoma (CDC-B). We have examined the potential difference in thrombocytopenia between patients with CLD-B and those with CLD-C in terms of liver fibrosis adjustment and splenomegaly.

METHODS

The study cohort consisted of 102 patients with CLD-B and 143 patients with CLD-C were enrolled. Liver stiffness, which is reported to be well correlated with the degree of liver fibrosis, was measured by transient elastography.

RESULTS

The analysis of covariance with liver stiffness as a covariate revealed that the platelet count was lower in CLD-C patients than in CLD-B patients. Following stratification for liver stiffness, thrombocytopenia was found to be more severe in CLD-C patients than CLD-B patients with advanced liver stiffness, whereas the degree of splenomegaly was not significantly different. The plasma thrombopoietin level was not different between CLD-B and CLD-C patients with advanced liver stiffness, and the immature platelet number was lower in CLD-C patients despite thrombocytopenia being more severe in these patients.

CONCLUSIONS

CLD-C patients with advanced liver stiffness presented with more severe levels of thrombocytopenia than CLD-B patients even with the same grade of splenomegaly. Impaired platelet production rather than enhanced platelet destruction may underlie the mechanism responsible for thrombocytopenia in patients with CLD.

Prognostic value of immature platelet fraction and plasma thrombopoietin in disseminated intravascular coagulation

Although platelet count is a good parameter for the diagnosis of disseminated intravascular coagulation (DIC), a single measurement of platelet is not enough to reflect the ongoing platelet consumption because of compensatory synthesis of circulating platelet number. Increased thrombopoiesis owing to peripheral destruction is expected in patients with DIC. Reticulated platelet, measured as immature platelet fraction (IPF), and plasma thrombopoietin (TPO) are markers of platelet production. We investigated the potential usefulness of circulating IPF and TPO in 222 patients suspected of having DIC. Both IPF and TPO levels were significantly increased in overt DIC patients and well correlated with DIC score. IPF also correlated with fibrin-related marker such as fibrinogen degradation product and D-dimer. Both IPF and TPO showed better mortality prediction than platelet count with the multivariate logistic regression and Kaplan-Meier survival analysis. These results suggest that IPF and TPO are new potential candidates to detect the severity of DIC and to predict DIC mortality.

The thrombocytopenia of WAS: a familial form of ITP?

In the first report of the concurrent immunodeficiency, thrombocytopenia, and eczema that we now call the Wiskott-Aldrich Syndrome (WAS), Alfred Wiskott asked whether it could be a familial form of Werlhof's disease (now called ITP). This review summarizes what is known about platelet production, consumption, and function in clinical and murine WAS. Both platelet production and consumption are affected by WASP deficiency. Likely molecular mechanisms have been identified for the former process, but remain problematic for the latter. Recent data in a murine model suggest that WASP deficiency could increase both the incidence of antiplatelet antibodies and susceptibility to their enhancement of platelet consumption. Wiskott's original speculation about the relationship between WAS and ITP may need to be reconsidered.

Immature platelet fraction measurement in patients with chronic liver disease: a convenient marker for evaluating cirrhotic change

Platelet number is often used as an indicator of the severity of liver disease. Although inadequate thrombopoietin production and decreased platelet production have been proposed as major causes of cirrhotic thrombocytopenia, the underlying mechanism has not yet been fully clarified. We examined whether the measurement of the immature platelet fraction (IPF) in thrombocytopenic patients with liver dysfunction is useful as a rapid and noninvasive method for the differential diagnosis of chronic liver diseases. We examined 20 liver cirrhosis patients, 56 patients with chronic hepatitis, 9 patients with fatty liver, and 86 patients without liver disease. The percentage value of IPF (IPF%) was measured using an XE-2100 multiparameter automatic hematology analyzer. Using a receiver operating characteristic curve, we found diagnostic significance of the absolute platelet count and the absolute number of the IPF between cirrhotic patients and noncirrhotic patients, and developed a powerful multivariate discriminant analysis (MDA) function based on the platelet count and the IPF%. The diagnostic accuracy obtained by the MDA function was superior to that obtained by the absolute number of platelets and the IPF. We therefore propose our IPF% measurement for the diagnosis of liver cirrhosis.

Immature platelet fraction (IPF) in hospitalized patients with neutrophilia and suspected bacterial infection

OBJECTIVES

Neutrophilia is frequently in hospitalized patients, so a screening test for infections would be very useful. The immature platelet fraction (IPF) is provided by the automated blood analyzer XE 2100 (Sysmex, Kobe, Japan) as a proportional value of the total optical platelet count [IPF%; an absolute count of immature platelets can also be obtained (AIPC)] to indicate the rate of platelet production. IPF could help to identify the aetiology of thrombocytopenia and to recognize the increased bone marrow activity as occurred during the course of infectious disease.

MATERIALS AND METHODS

We selected from daily routine cell blood counts 535 samples from adult patients (age >14 years) with neutrophilia (> 8 x 10(9)/L) and platelets > or =150 x 10(9)/L, to avoid bias due to physiological increase of IPF. In 153 patients blood cultures (BC) were done the same day of IPF determination because of clinically suspected infection (fever > or =38 degrees C).

RESULTS

Eighty-nine samples (58.2%) had positive BC (75 Gram-positive agents, 14 Gram-negative). Using our IPF reference normal range [IPF% 2.39% (0.8-5.1); AIPC 5.15 x 10(9)/L (2-12.6)], we found a significantly (p<0.0001) higher level of IPF in samples with positive BC [mean IPF% 4.86+/-2.67%, median 3.8 (range 2.4-15.8); mean AIPC 14.74+/-9.26 x 10(9)/L, median 11.7, (range 4.7-44.9)] than in BC negative samples [mean IPF% 1.79+/-0.63%, median 1.7 (range 0.5-4.7); mean AIPC 6.55+/-3.58 x 10(9)/L, median 5.45 (range 1.6-20.4)].

CONCLUSIONS

The increased IPF shows a statistically significant correlation with BC positivity. This parameter could therefore be used in the daily laboratory routine in patients with neutrophilia as a low cost screening test for bacterial infection.

Evaluation of platelet turnover by flow cytometry

The number of circulating newly produced platelets depends on the thrombopoietic capacity of bone marrow as well as platelet removal from the bloodstream. Flow cytometric analysis with thiazole orange (TO), a fluorescent dye that crosses platelet membranes and binds intracellular RNA, has been used to measure circulating reticulated platelets (RPs) with high RNA content as an index of platelet turnover. We first assessed the specificity of TO flow cytometry and then applied this method in the diagnosis of thrombocytopenia caused by impaired platelet production or increased destruction. We also explored the utility of TO flow cytometry to predict thrombocytopoiesis after chemotherapy-induced bone marrow aplasia. Venous blood, anticoagulated with K(2)EDTA, was incubated with 0.6 microg/ml TO plus an anti-GPIIIa monoclonal antibody. The mean percentage of RPs in control subjects (n = 23) was 6.13 +/- 3.09%. RPs were 10.41 +/- 9.02% in patients (n = 10) with hematological malignancies during aplasia induced by chemotherapy and a significant increase in RPs (35.45 +/- 6.11%) was seen in the recovery phase. In 10 patients with idiopathic thrombocytopenic purpura, the percentage of TO positive platelets was 67.81 +/- 18.79 (P < 0.001 vs. controls). In patients with thrombocytopenia associated with hepatic cirrhosis (n = 21; 21.04 +/- 16.21%, P < 0.001 vs. controls) or systemic lupus erythematosus (n = 6, 29.08 +/- 15.57%; P < 0.001 vs. controls) increases in TO-stained platelets were also observed. Measurement of TO positive platelets may be a reliable tool for the laboratory identification of platelet disorders, with a higher sensitivity than measurement of platelet volume. Measurement of RPs may also prove useful to recognize the underlying pathogenetic mechanisms in thrombocytopenia.