Low immature platelet fraction suggests decreased megakaryopoiesis in neonates with sepsis or necrotizing enterocolitis

The role of platelets and megakaryocytes in sepsis and ARDS

Since the global COVID-19 pandemic, there has been a renewed focus on lung injury during infection. Systemic inflammatory responses such as acute respiratory distress syndrome (ARDS) and sepsis are a leading cause of morbidity and mortality for both adults and children. Improvements in clinical care have improved outcomes but mortality remains ∼40% and significant morbidity persists for those patients with severe disease. Mechanistic studies of the underlying biological processes remain essential to identifying therapeutic targets. Furthermore, methods for identifying the underlying drivers of organ failure are key to treating and preventing tissue injury. In this review, we discuss the contribution of megakaryocytes (MKs) and platelets to the pathogenesis of systemic inflammatory syndromes. We explore the role of MKs and the new identification of extramedullary MKs during sepsis. We describe the alterations in the platelet transcriptome during sepsis. Lastly, we explore platelet function as defined by aggregation, activation and the formation of heterotypic aggregates. Much more work is necessary to explore the contribution of platelets to these heterogenous syndromes, but the foundation of platelets as key contributors to inflammation has been laid.

Immature platelet counts in transfused platelet units given to neonates

BACKGROUND

Immature platelets, young and large platelets recently released from the bone marrow, have gained interest over the last decade as a clinically informative variable during thrombocytopenic presentations. These immature platelets are found in all donated platelet units, however, the role, if any, that these younger platelets play post transfusion is not known. It has also been reported that the immune response can affect responses to platelet transfusions. Thus, we looked at PLT increments in a cohort of neonates receiving platelet transfusions in our neonatal intensive care unit.

METHODS

During a twelve-month period, platelet transfusions received by neonates born and not discharged from our institution at time of transfusion were retrospectively analyzed. In the study period a total of 33 patients received either a single or multiple transfusions during their hospitalization, for a total of 100 transfusion events.

RESULTS

The cohort was mostly premature neonates with a mean gestational age of 29.6 weeks. The units transfused appeared to have a broad range of absolute immature platelet counts (A-IPC) but overall, it was similar between those receiving single or multiple transfusions. Considering that platelet count was similar among aliquots transfused, it appeared that count increments were influenced by higher A-IPC content of the aliquot especially among 2nd trimester and 3rd trimester premature neonates. Patients with higher baseline platelet count (PLT) tended to receive a single transfusion aliquot while those receiving multiple transfusions had lower baseline PLT (p = 0.0022). Looking at aliquot dose, regardless if receiving a single or multiple transfusions, younger patients received incrementally higher dose (ml/kg) with each transfusion.

CONCLUSIONS

A-IPC in platelet aliquots transfused to neonates may influence post-transfusion PLT. Full effect of A-IPC in platelet aliquots may not be seen since irradiation of units may hamper immature platelets viability and function. Further research is needed to determine if A-IPC plays an active role to limit the need for further transfusions of patients receiving transfusions.

Alterations in the megakaryocyte transcriptome impacts platelet function in sepsis and COVID-19 infection

Platelets and their parent cell, the megakaryocyte (MK), are increasingly recognized for their roles during infection and inflammation. The MK residing in the bone marrow or arising from precursors trafficked to other organs for development go on to form platelets through thrombopoiesis. Infection, by direct and indirect mechanisms, can alter the transcriptional profile of MKs. The altered environment, whether mediated by inflammatory cytokines or other signaling mechanisms results in an altered platelet transcriptome. Platelets released into the circulation, in turn, interact with each other, circulating leukocytes and endothelial cells and contribute to the clearance of pathogens or the potentiation of pathophysiology through such mechanisms as immunothrombosis. In this article we hope to identify key contributions that explore the impact of an altered transcriptomic landscape during severe, systemic response to infection broadly defined as sepsis, and viral infections, including SARS-CoV2. We include current publications that outline the role of MKs from bone-marrow and extra-medullary sites as well as the circulating platelet. The underlying diseases result in thrombotic complications that exacerbate organ dysfunction and mortality. Understanding the impact of platelets on the pathophysiology of disease may drive therapeutic advances to improve the morbidity and mortality of these deadly afflictions.

Immature Platelet Fraction and Its Kinetics in Neonates

Thrombocytopenia is a common abnormality encountered in the neonatal period, and immature platelet fraction (IPF) may be an informative indicator of thrombopoiesis; however, data on IPF in neonates are scarce. To define reference intervals (RIs) and factors affecting IPF in neonates, we measured the IPF of 533 consecutive neonates. With a multiple regression analysis of 330 newborns with normal platelet counts at birth, premature delivery, neonatal asphyxia, intrauterine infection, chromosomal abnormalities, and respiratory disorders were identified as independent factors for IPF%. The RIs of IPF% and absolute IPF value in neonates were determined to be 1.3% to 5.7% and 3.2 to 14.5×10 9 /L, respectively. On day 14 after birth, IPF% increased to twice the value at birth and thereafter returned to the previous value on day 28. Reticulocyte counts, in contrast, were the lowest at day 14. IPF% was increased in 16 thrombocytopenic patients with various clinical conditions, especially those with immune-mediated thrombocytopenia. IPF in neonates may be evaluated essentially based on the same RIs as in adults, although some precautions must be taken when evaluating IPF in neonates in the first 2 weeks of life. IPF may be useful for evaluating thrombopoiesis and thrombocytopenia in neonates.

Gestational age-specific hematological patterns in preterm infants following necrotizing enterocolitis

OBJECTIVE

To investigate gestational age (GA) specific hematological and transfusion response patterns in preterm infants following necrotizing enterocolitis (NEC).

DESIGN

A retrospective study comparing hematological/transfusion information in three GA groups' infants: Group A ≤ 28 weeks. Group B 28-32 weeks, Group C > 32 weeks following necrotizing enterocolitis.

RESULTS

Group A infants responded with significantly higher WBC count, thrombocytopenia, higher absolute neutrophil, and higher absolute monocyte and lower absolute lymphocyte counts following NEC onset, received more blood transfusions before NEC onset (59.8 versus 30.0%; p = .007), and had higher odds of surgical NEC (OR 3.39 [95% CI 1.19-10.38]; p = .02) than group C. One unit increase in absolute lymphocyte count on the day, and 24 h following NEC was significantly associated with lower surgical NEC odds than groups C.

CONCLUSION

The infant's in-group A had significantly different hematological response patterns following NEC than infants with higher gestational age (groups B and C).

Changes in Platelet Function in Preterm Newborns with Prematurity Related Morbidities

Platelet indices represent useful biomarkers to express the thromboembolic status, inflammatory response, and oxidative stress in preterm newborns. Our study presented platelet count and function changes in prematurity-related morbidities such as respiratory distress syndrome, intraventricular bleeding, and anemia of prematurity in preterm newborn cases reported to healthy full-term newborns by flow cytometry and hematological methods. The platelet volume represents the average size of platelets in the blood samples, showing the significantly increased values in preterm newborns compared with healthy full-term newborns due to increasing activated platelet production. Flow cytometric analysis of immature platelet fractions (IPF) made using thiazole orange staining to detect their mRNA content and a glycoprotein (anti-GPIIIa) antibody for platelet gating. CD61-TO expression from premature newborns was significantly lower compared to healthy full-term neonates. Preterm newborn cases with respiratory distress syndrome and a need for respiratory support (RDS+) were characterized by a significantly increased platelet volume and a decreased immature platelet fraction reported in RDS− cases. Evaluating the platelet function in the newborn is difficult because the laboratory methodologies work with small quantities of newborn blood samples. The immature platelet fractions and platelet volume promise to be diagnostic biomarkers for diseases.

Platelets in pediatric and neonatal sepsis: novel mediators of the inflammatory cascade

Sepsis, a dysregulated host response to infection, has been difficult to accurately define in children. Despite a higher incidence, especially in neonates, a non-specific clinical presentation alongside a lack of verified biomarkers has prevented a common understanding of this condition. Platelets, traditionally regarded as mediators of haemostasis and thrombosis, are increasingly associated with functions in the immune system with involvement across the spectrum of innate and adaptive immunity. The large number of circulating platelets (approx. 150,000 cells per microlitre) mean they outnumber traditional immune cells and are often the first to encounter a pathogen at a site of injury. There are also well-described physiological differences between platelets in children and adults. The purpose of this review is to place into context the platelet and its role in immunology and examine the evidence where available for its role as an immune cell in childhood sepsis. It will examine how the platelet interacts with both humoral and cellular components of the immune system and finally discuss the role the platelet proteome, releasate and extracellular vesicles may play in childhood sepsis. This review also examines how platelet transfusions may interfere with the complex relationships between immune cells in infection. IMPACT: Platelets are increasingly being recognised as important "first responders" to immune threats. Differences in adult and paediatric platelets may contribute to differing immune response to infections. Adult platelet transfusions may affect infant immune responses to inflammatory/infectious stimuli.

Role of platelets in neonatal necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is an inflammatory bowel necrosis of premature infants and is a leading cause of morbidity and mortality in infants born between 23 and 28 weeks of gestation. Fifty to 95% of all infants with NEC develop thrombocytopenia (platelet counts <150 × 109/L) within 24-72 h of receiving this diagnosis. In many patients, thrombocytopenia is severe and is treated with one or more platelet transfusions. However, the underlying mechanism(s) and biological implications of NEC-related thrombocytopenia remain unclear. This review presents current evidence from human and animal studies on the clinical features and mechanisms of platelet depletion in NEC. Anecdotal clinical experience is combined with evidence from laboratory studies and from an extensive literature search in databases PubMed, EMBASE, and Scopus and the electronic archives of abstracts presented at the annual meetings of the Pediatric Academic Societies. To avoid bias in identification of existing studies, key words were short-listed prior to the actual search both from anecdotal experience and from PubMed's Medical Subject Heading (MeSH) thesaurus. IMPACT: Fifty to 95% of infants with necrotizing enterocolitis (NEC) develop idiopathic thrombocytopenia (platelet counts <150 × 109/L) within 24-72 h of disease onset. Early clinical trials suggest that moderate thrombocytopenia may be protective in human NEC, although further work is needed to fully understand this relationship. We have developed a neonatal murine model of NEC-related thrombocytopenia, where enteral administration of an immunological stimulant, trinitrobenzene sulfonate, on postnatal day 10 induces an acute necrotizing ileocolitis resembling human NEC. In this murine model, thrombocytopenia is seen at 15-18 h due to platelet consumption and mild-moderate thrombocytopenia is protective.

Hematological predictors of mortality in neonates with fulminant necrotizing enterocolitis

OBJECTIVE

Determine whether hematological and transfusion patterns following, the onset of NEC can identify infants likely to develop fulminant, fatal necrotizing enterocolitis (NEC).

DESIGN

Determine hematological predictors of fulminant NEC.

RESULTS

Of 336 neonates with NEC, 35 (10%) who developed fulminant NEC were born with higher birth weights and more frequently developed radiologically evident pneumoperitoneumand/or portal venous gas. Following the diagnosis of NEC, these infants were more likely to rapidly develop thrombocytopenia, lymphopenia, neutropenia, and lower total white blood cell counts compared to medical/surgical non-fulminant type. They were also more likely to have received a red blood cell (RBC) transfusion (76.7% vs. 53.1%, p = 0.001) within 48 h after disease onset and platelet transfusion (24.2% vs. 11.7%; p = 0.03) before the onset of NEC.

CONCLUSION

Neonates with fulminant NEC frequently developed thrombocytopenia, lymphopenia, neutropenia, and leukopenia, received RBC transfusions after or platelet transfusions before the onset of NEC developed the fulminant disease.

Immature Platelet Counts and Thrombopoietin Plasma Concentrations in Thrombocytopenic and Non-thrombocytopenic Preterm Infants

Objective: Immature platelet counts (IPC) may prove useful in guiding platelet transfusion management in preterm neonates. However, the relationship between IPCs and thrombopoietin (Tpo) concentrations has not been evaluated in preterm neonates. Methods: Prospective cohort study in thrombocytopenic (n = 31) and non-thrombocytopenic very low birth weight (VLBW) infants (n = 38), and healthy term neonates (controls; n = 41). Absolute platelet counts (APCs), IPCs, and Tpo concentrations were assessed by a fully-automated hematological analyzer (IPC, APC) and by ELISA (Tpo concentrations) in parallel on day 1 of life (d1), d3, and d7. Results: In healthy term neonates, APCs remained stable between d1 and d3. In non-thrombocytopenic VLBW infants, APCs increased from d1 to d7, while in the thrombocytopenia group, APCs declined from d1 to d3, before they slightly increased again by d7. Median IPCs were similar in healthy term vs. non-thrombocytopenic VLBW infants and remained stable between d1 and d3 (p > 0.05). Notably, IPCs significantly increased between d3 and d7 in both non-thrombocytopenic and thrombocytopenic VLBW infants. However, in thrombocytopenic VLBW infants, IPC values were significantly lower at each time point as compared to non-thrombocytopenic VLBWs (p < 0.001). In each subgroup, Tpo concentrations increased from d1 to d3. The median Tpo concentrations were significantly higher in thrombocytopenic as compared to non-thrombocytopenic VLBW infants at d3 (p = 0.01) and d7 (p = 0.002). Discussion: Term infants, thrombocytopenic, and non-thrombocytopenic preterm infants display similar developmental changes in indices of megakaryopoietic activity. In thrombocytopenic preterm infants, however, the responsive increases in Tpo and immature platelets appear to be developmentally limited.

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.

Haematopoietic alterations in neonates with congenital diaphragmatic hernia receiving extracorporeal membrane oxygenation support

BACKGROUND

Extracorporeal membrane oxygenation procedure (ECMO) has been established in the therapy of respiratory insufficient infants with congenital diaphragmatic hernia. In congenital diaphragmatic hernia newborns, a delay in transfer to an ECMO centre is associated with a sharp increase in mortality. Predictive factors for ECMO support are urgently needed. We evaluated the routine parameters of the first blood withdrawal after birth in congenital diaphragmatic hernia infants, hypothesizing that early signs in bone marrow affecting haematology parameters for early regulation of potentially post birth hypoxia are predictive factors for ECMO support.

MATERIALS AND METHODS

In 44 patients born with congenital diaphragmatic hernia, differential blood cell count from the first blood withdrawal after birth was examined. Descriptive statistics included median, 95% confidence intervals, minimum and maximum differentiating ECMO/early mortality vs. no ECMO. Odds ratios with CI were calculated by binary logistic regression analysis. Best predictive markers were further checked in combination with the liver-up situation in two factorial regression models.

RESULTS

In our cohort, the survival rate was 77.3% (34/44). While 18 neonates received ECMO support, 26 experienced no ECMO during hospital stay. Odds ratio calculations showed that risk for ECMO support increases with augmenting leukocytes, erythrocytes, haemoglobin, haematocrit, mean cell volume and absolute immature granulocytes. Further, the risk advanced in line with the severity of congenital diaphragmatic hernia assessed by prenatal ultrasound.

CONCLUSIONS

We conclude that these parameters are associated with disease severity in congenital diaphragmatic hernia newborns and may be considered potentially predictive biomarkers for the necessity of ECMO support.

Tie2 protects the vasculature against thrombus formation in systemic inflammation

Disordered coagulation contributes to death in sepsis and lacks effective treatments. Existing markers of disseminated intravascular coagulation (DIC) reflect its sequelae rather than its causes, delaying diagnosis and treatment. Here we show that disruption of the endothelial Tie2 axis is a sentinel event in septic DIC. Proteomics in septic DIC patients revealed a network involving inflammation and coagulation with the Tie2 antagonist, angiopoietin-2 (Angpt-2), occupying a central node. Angpt-2 was strongly associated with traditional DIC markers including platelet counts, yet more accurately predicted mortality in 2 large independent cohorts (combined N = 1,077). In endotoxemic mice, reduced Tie2 signaling preceded signs of overt DIC. During this early phase, intravital imaging of microvascular injury revealed excessive fibrin accumulation, a pattern remarkably mimicked by Tie2 deficiency even without inflammation. Conversely, Tie2 activation normalized prothrombotic responses by inhibiting endothelial tissue factor and phosphatidylserine exposure. Critically, Tie2 activation had no adverse effects on bleeding. These results mechanistically implicate Tie2 signaling as a central regulator of microvascular thrombus formation in septic DIC and indicate that circulating markers of the Tie2 axis could facilitate earlier diagnosis. Finally, interventions targeting Tie2 may normalize coagulation in inflammatory states while averting the bleeding risks of current DIC therapies.

Time course of immature platelet count and its relation to thrombocytopenia and mortality in patients with sepsis

Introduction

The pathogenesis of thrombocytopenia in patients with sepsis is not fully understood. The aims of this study were to investigate changes in thrombopoietic activity over time by using absolute immature platelet counts (AIPC) and to examine the impact of platelet production on thrombocytopenia and mortality in patients with sepsis.

Methods

This retrospective observational study included adult patients with sepsis admitted to the intensive care unit at a university hospital. Two hundred five consecutive sepsis patients were stratified into four groups according to nadir platelet count: severe (nadir ≤40×10³/μL), moderate (41–80×10³/μL), or mild thrombocytopenia (81–120×10³/μL), or normal-increased platelet count (>120×10³/μL). The development of thrombocytopenia was assessed during the first week; mortality was assessed at day 28.

Result

Of the 205 patients included, 61 (29.8%) developed severe thrombocytopenia. On admission, AIPC did not differ among the four groups. In patients with severe thrombocytopenia, AIPC decreased significantly from days 2 to 7, but remained within or above the normal range in the other three groups (overall group comparison, P<0.0001). Multivariate analysis including coagulation biomarkers revealed that AIPC was independently associated with the development of severe thrombocytopenia (day 3 AIPC, odds ratio 0.49 [95% confidence interval (CI) 0.35–0.66], P<0.0001; day 5 AIPC, 0.59 [95% CI 0.45–0.75], P<0.0001). AIPC was a significant predictor of 28-day mortality in Cox hazard models adjusted for Acute Physiology and Chronic Health Evaluation II and Sequential Organ Failure Assessment scores (day 3 AIPC, hazard ratio 0.70 [95% CI 0.52–0.89], P = 0.0029; day 5 AIPC, 0.68 [95% CI 0.49–0.87], P = 0.0012).

Conclusions

Thrombopoietic activity was generally maintained in the acute phase of sepsis. However, a decrease in AIPC after admission was independently associated with the development of severe thrombocytopenia and mortality, suggesting the importance of suppressed thrombopoiesis in the pathophysiology of sepsis-induced thrombocytopenia.

The immature platelet fraction: creating neonatal reference intervals and using these to categorize neonatal thrombocytopenias

OBJECTIVE

The immature platelet fraction (IPF) is a laboratory measurement analogous to the reticulocyte count, but reflecting the thrombopoietic state. Similar to a reticulocyte count, it can be expressed as a percent (IPF%=percent of platelets that are immature) or as an absolute number per μl blood; the immature platelet count (IPC=IPF% × platelets per μl of blood).

STUDY DESIGN

Using a retrospective analysis of de-identified data from non-thrombocytopenic neonates, we created reference intervals for IPF% and IPC. We then tested the value of these measurements for categorizing thrombocytopenic neonates.

RESULTS

New charts display reference intervals for IPF% and IPC on the day of birth according to gestational age, and during the first 90 days after birth. Neonates with hyporegenerative varieties of thrombocytopenias (syndromes, small for gestational age, birth asphyxia) had lower IPF% and IPC than did neonates with consumptive thrombocytopenias (immune-mediated, infection, disseminated intravascular coagulation, necrotizing enterocolitis; both P<0.0001).

CONCLUSION

The new reference interval charts can be used to recognize abnormal IPFs. The IPF parameters can help clarify the kinetic mechanism responsible for thrombocytopenias in neonates.

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.

Developmental differences between newborn and adult mice in response to romiplostim

Thrombocytopenia is frequent among sick neonates. While most cases are transient, some neonates experience prolonged and severe thrombocytopenia. These infants often pose diagnostic and therapeutic challenges, and may receive large numbers of platelet transfusions. Romiplostim (ROM) is a thrombopoietin (TPO)-receptor-agonist approved for treatment of adults with chronic immune thrombocytopenia (ITP). The immature platelet fraction (IPF) is a novel measure of newly produced platelets, which could aid with the diagnostic evaluation of thrombocytopenic neonates. This study had the following two objectives: (1) compare the response of newborn and adult mice to escalating doses of ROM in vivo and (2) assess the correlation between IPF and megakaryocyte (MK) mass in newborn and adult treated and untreated mice. In the first set of studies, newborn (day 1) and adult mice received a single subcutaneous (SC) dose of ROM ranging from 0 to 300 ng/g, and platelet counts were followed every other day for 14 days. Both sets of mice responded with dose-dependent platelet and IPF increases, peaking on days 5-7 post-treatment, but neonates had a blunted response (2.1-fold compared to 4.2-fold maximal increase in platelet counts, respectively). On day 5 post-treatment with 300 ng/g ROM, MKs in the bone marrow (BM) and spleen of adult mice were significantly increased in numbers and size (p < 0.0001 for both) compared to controls. MKs in the spleen and BM (but not liver) of treated neonates also increased in number, but not in size. The immature platelet count (IPC, calculated as IPF x platelet count) was highly correlated with the MK number and size in neonatal and adult BM and spleen, but not neonatal liver. The lack of response of neonatal liver MKs was not due to a cell-intrinsic reduced responsiveness to TPO, since neonatal liver progenitors were more sensitive to murine TPO (mTPO) in vitro than adult BM progenitor. In vivo treatment of newborn mice with high mTPO doses or with higher doses of ROM (900 ng/g) resulted in peak platelet counts approaching 3-fold of controls. Taken together, our data indicate that newborn mice are less responsive to ROM than adult mice in vivo, due to a combination of likely pharmacokinetic differences and developmental differences in the response of MKs to thrombopoietic stimulation, evidenced by neonatal MKs increasing in numbers but not in size. PK/PD studies in human infants treated with ROM are warranted.

Neonatal mice with necrotizing enterocolitis-like injury develop thrombocytopenia despite increased megakaryopoiesis

BACKGROUND

Thrombocytopenia is frequently encountered in infants with necrotizing enterocolitis (NEC). To develop a preclinical model of NEC-related thrombocytopenia, we measured serial platelet counts in 10-d-old (P10) mouse pups with trinitrobenzene sulfonic acid (TNBS)-induced NEC-like injury. We also measured platelet volume indices, immature platelet fraction (IPF), and megakaryocyte number/ploidy in these animals.

METHODS

Platelet counts, platelet volume indices, and IPF were measured in control (N = 65) and TNBS-treated pups (N = 104) using an automated hematology analyzer. Bone marrow megakaryocyte number, ploidy and CD41 expression were measured by flow cytometry. These findings were confirmed in a small cohort of P3 mice with NEC-like injury.

RESULTS

Murine pups with TNBS-mediated NEC-like injury developed thrombocytopenia at 15-24 h after exposure to TNBS. Intestinal injury was associated with increased platelet volume indices (mean platelet volume, platelet-to-large cell ratio, and platelet distribution width), and IPF, indicating increased thrombopoiesis. These mice also showed increased megakaryocyte number, ploidy, and CD41 expression, indicating increased megakaryocyte differentiation.

CONCLUSION

Similar to human NEC, murine NEC-like injury was also associated with decreased platelet counts. There was evidence of increased megakaryocyte differentiation and thrombopoiesis, which favors peripheral consumption of platelets as the likely mechanism of thrombocytopenia in these animals, over decreased platelet production.

Determination of reference ranges for immature platelet and reticulocyte fractions and reticulocyte hemoglobin equivalent

Introduction

The immature platelet and immature reticulocyte fractions represent the ratios of platelets and reticulocytes recently released into the circulation and thus with higher RNA content. They are considered early indicators of bone marrow recovery.

Objective

The aim of this study was to determine the reference ranges for the immature platelet and reticulocyte fractions of hematologically normal individuals in a university hospital.

Methods

Venous blood samples collected in ethylenediaminetetraacetic acid K3 were analyzed using a Sysmex XE-5000™ analyzer. Individuals with platelet and reticulocyte counts within the reference ranges, and a blood count within the laboratory's screening criteria were included. Individuals with clinical conditions that could affect hematological results were excluded. The immature platelet fraction, high, medium and low fluorescence reticulocyte fractions and reticulocyte hemoglobin equivalent were evaluated. The reference ranges were determined according to the recommendations of the International Federation of Clinical Chemistry.

Results

One hundred and thirty-two outpatients were evaluated. The mean age was 44 years (range: 13–80 years), 72 (54.5%) were women treated in a university hospital. The mean platelet count was 250.8 × 10⁹/L and the mean reticulocyte count was 0.052 × 10⁹/L. The following reference ranges were obtained: immature reticulocyte fraction 1.6–12.1%, the high, medium and low fluorescence reticulocyte fractions were 0.0–1.7%, 1.6–11.0% and 87.9–98.4%, respectively, the reticulocyte hemoglobin equivalent was 30.0–37.6% and immature platelet fraction was 0.8–5.6%. There was a statistically significant difference (p-value = 0.006) between genders in respect to the immature platelet fraction with 0.8–4.7% for females and 0.7–6.1% for males. The immature reticulocyte fraction was directly correlated with the reticulocyte count.

Conclusion

Determining the reference range is critical to the introduction of a new parameter. The reference ranges obtained herein corroborate those reported in previous publications and will contribute to the clinical and laboratory application of the indices.

Thrombocytopenia and platelet transfusion in the neonate

Neonatal thrombocytopenia is widespread in preterm and term neonates admitted to neonatal intensive care units, with up to one-third of infants demonstrating platelet counts <150 × 10(9)/L. Thrombocytopenia may arise from maternal, placental or fetal/neonatal origins featuring decreased platelet production, increased consumption, or both mechanisms. Over the past years, innovations in managing neonatal thrombocytopenia were achieved from prospectively obtained clinical data on thrombocytopenia and bleeding events, animal studies on platelet life span and production rate and clinical use of fully automated measurement of reticulated platelets (immature platelet fraction). This review summarizes the pathophysiology of neonatal thrombocytopenia, current management including platelet transfusion thresholds and recent developments in megakaryopoietic agents. Furthermore, we propose a novel index score for bleeding risk in thrombocytopenic neonates to facilitate clinician's decision-making when to transfuse platelets.

Platelet Mass Predicts Intracranial Hemorrhage in Neonates With Gram-negative Sepsis

Neonatal sepsis due to gram-negative bacteria is associated with severe hemorrhagic conditions, such as intracranial hemorrhage (ICH). The aim of the study was to investigate the significance of platelet (PLT) count and platelet mass (PM) in predicting promptly neonatal ICH. Demographics, species, PLT, PM, ICH, and outcome for neonates with gram-negative sepsis for the period 2005 to 2012 were retrospectively recorded. Eighty-four infants were enrolled with median gestational age 30 weeks, median birthweight 1481.5 g, and median age at sepsis diagnosis 23 days. The most frequently isolated bacteria were Enterobacter spp. (38.1%). ICH occurred in 16 neonates (19%), whereas the mortality rate was 25% (21 neonates). The median PLT count and PM at days 1, 2, and 3 after diagnosis of gram-negative sepsis was significantly associated with the presence of ICH. Regression analysis revealed the cutoff predictive value of 355 fL/nL for the PM at day 3 (area under the curve: 75, sensitivity 90%, P=0.002). PM levels could play an important role in predicting the occurrence of ICH in high-risk neonates.

Hematologic Aspects of Early and Late-Onset Sepsis in Preterm Infants

This article reviews and updates the state of the art on the hematologic aspects related to neonatal sepsis in preterm neonates in the neonatal intensive care unit and overviews all hematologic changes occurring during neonatal infections and their implications both as diagnostic and prognostic parameters to guide clinicians at the patients' bedside.

Evaluation and management of thrombocytopenic neonates in the intensive care unit

Thrombocytopenia is a very frequent problem among sick neonates, affecting up to 35% of all infants admitted to the neonatal intensive care unit (NICU), and serves as an important indicator of multiple clinical conditions. The cause of the thrombocytopenia is unclear in up to 60% of affected neonates. A clinical classification of thrombocytopenia is based on the time of presentation, early (≤72 hours of life) vs. late (>72 hours of life). Early thrombocytopenia is commonly associated with feto-maternal conditions, is most commonly caused by disorders associated with placental insufficiency, and is generally mild to moderate and resolves spontaneously within 7-10 days without any intervention. In contrast, neonates who develop late-onset thrombocytopenia frequently have bacterial sepsis or necrotizing enterocolitis. It is often severe (platelets <50,000/μL), prolonged and frequently requires multiple platelet transfusions. Platelet transfusions represent the only specific therapy currently available for most thrombocytopenic neonates, even though much evidence suggests that platelet transfusions are not benign. Many of the prophylactic platelet transfusions currently given to NICU patients are unnecessary, convey no benefits, and carry known and unknown risks. For this reason, pharmacological alternatives have been investigated as potential therapies for thrombocytopenia, but they still have limited use treating the common varieties of neonatal thrombocytopenia.