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.

Pathological Mechanisms and Novel Testing Methods in Thrombotic Thrombocytopenic Purpura.

Thrombotic thrombocytopenic purpura (TTP) is an uncommon, but potentially disabling or even deadly, thrombotic microangiopathy with a well-studied mechanism of ADAMTS13 deficiency or dysfunction. While established treatments are largely effective, the standard ADAMTS13 testing required to definitively diagnose TTP may cause delays in diagnosis and treatment, highlighting the need for rapid and effective diagnostic methods. Additionally, the heterogeneous presentation and varied inciting events of TTP suggest more variation in its mechanism than previously thought, implying three potential pathways rather than the accepted two. The recent discovery of ADAMTS13 conformation as a potential contributor to TTP in addition to the proposal of using the absolute immature platelet count (A-IPC) as a biomarker, present novel areas for monitoring and treatment. A-IPC in particular may serve as a more rapid and accurate diagnostic test to distinguish TTP from non-TTP TMAs and to monitor treatment response and relapse. These considerations highlight the need to further study TTP in order to improve best practices and patient care.

Bacterial Contamination of Platelet Products.

Transfusion of bacterially contaminated platelets, although rare, is still a major cause of mortality and morbidity despite the introduction of many methods to limit this over the past 20 years. The methods used include improved donor skin disinfection, diversion of the first part of donations, use of apheresis platelet units rather than whole-blood derived pools, primary and secondary testing by culture or rapid test, and use of pathogen reduction. Primary culture has been in use the US since 2004, using culture 24 h after collection of volumes of 4-8 mL from apheresis collections and whole-blood derived pools inoculated into aerobic culture bottles, with limited use of secondary testing by culture or rapid test to extend shelf-life from 5 to 7 days. Primary culture was introduced in the UK in 2011 using a "large-volume, delayed sampling" (LVDS) protocol requiring culture 36-48 h after collection of volumes of 16 mL from split apheresis units and whole-blood derived pools, inoculated into aerobic and anaerobic culture bottles (8 mL each), with a shelf-life of 7 days. Pathogen reduction using amotosalen has been in use in Europe since 2002, and was approved for use in the US in 2014. In the US, recent FDA guidance, effective October 2021, recommended several strategies to limit bacterial contamination of platelet products, including pathogen reduction, variants of the UK LVDS method and several two-step strategies, with shelf-life ranging from 3 to 7 days. The issues associated with bacterial contamination and these strategies are discussed in this review.

Apheresis collection of mononuclear cells for chimeric-antigen receptor therapies.

Collections of lymphocytes to be genetically modified to treat hematologic malignancies have seen a dramatic increase over the last few years as commercial products have been approved. Reports of new products in development that can possibly treat solid organ malignancies represent a massive change in the field. Apheresis is at the center of the collection of cells for the manufacture of these chimeric-antigen receptor therapy products. The expansion of these collections represents one of the areas of apheresis procedures growth. This review will summarize concepts important to this type of collection and variables that need to be optimized to obtain desired cell yields while increasing patients' safety.

Comparison of absolute immature platelet count to the PLASMIC score at presentation in predicting ADAMTS13 deficiency in suspected thrombotic thrombocytopenic purpura.

INTRODUCTION: Thrombotic thrombocytopenic purpura (TTP) demands rapid initiation of therapeutic plasma exchange to avoid severe complications associated with it. ADAMTS13 activity <10% defines TTP, however, this is a send-out test at most institutions. We have previously reported our experience looking at absolute immature platelet counts (A-IPC) in TTP patients. Thus, we compared A-IPC on admission to the PLASMIC score to predict ADAMTS13 deficiency. MATERIALS AND METHODS: Of seventy-two patients identified, 52 met inclusion criteria. All patients were suspected of new-onset TTP and had A-IPC on admission. Of these patients, 25/52 were later shown to have ADAMTS13 <10%, defined as TTP group, and 27/52 had ADAMTS13 >10% and are henceforth classified as non-TTP. RESULTS: Patients with TTP were found to have A-IPC below reference range (<1.5 × 109/L) and responded to therapy as shown by fold-increases in A-IPC (p < 0.0001), neither seen in non-TTP patients. A-IPC had a significant correlation with ADAMTS13 deficiency (p = 0.0001) with high sensitivity, specificity, positive and negative predictive values. Comparison of A-IPC to PLASMIC score indicated that the former identified all TTP patients compared to PLASMIC score even in patients obtaining scores of 4 and 5. Finally, Receiver Operating Characteristic curves showed A-IPC had area under the curve of 0.986. CONCLUSIONS: A-IPC below reference range and A-IPC fold-increases were only observed in TTP patients. There was strong association between A-IPC and ADAMTS13 deficiency and A-IPC predicted patients with ADAMTS13 deficiency. Future larger studies are needed to determine ways to apply findings in suspected TTP patients.

Anti-CD20 therapeutic options in immune-mediated thrombotic thrombocytopenic purpura.

Immunosuppression with rituximab in immune-mediated thrombotic thrombocytopenic purpura helps decrease production of autoantibody mediating ADAMTS13 clearance from circulation. Failure to respond to rituximab in a satisfactory way or made difficult by adverse events to the medication does not represent a reason to stop considering anti-CD20 therapies to control antibody production. Therefore, both of atumumab and obinutuzumab with specificity to CD20, represent potentially valuable therapeutic tools in patients who are not candidates for rituximab. Commentary on: Doyle et al. The use of obinutuzumab and ofatumumab in the treatment of immune thrombotic thrombocytopenic purpura. Br J Haematol. 2022;198:391-396.1.

Initial assessment of α-synuclein structure in platelets.

Over the last few years data from our group have indicated that α-synuclein is important in development of immune cells as well as potentially erythrocytes and platelets. The latter is important since this protein may work as negative regulator of granule release. Thus, we sought to begin to understand the structure of this protein in platelets. Flow cytometric analysis of this protein using region-specific (N-terminus, central region and C-terminus) monoclonal antibodies was performed. Antibody to the central region gave the strongest shift among all three antibodies, with the C-terminus having intermediate shift and N-terminus minimal shift. Western blotting using the same antibodies showed similar binding of all antibodies to α-synuclein. These results suggest a similar arrangement of this protein in platelets as seen in neurons. Future studies ought to look at the role that each protein region plays in platelets.

Absolute Immature Platelet Counts Suggest Platelet Production Suppression during Complicated Relapsing Thrombotic Thrombocytopenic Purpura.

Absolute immature platelet counts (A-IPC) aid in diagnosis and treatment follow-up in thrombotic thrombocytopenic purpura (TTP). A-IPC was used to follow a patient on mycophenolate mofetil (MMF) maintenance therapy treated with a prolonged therapeutic plasma exchange (TPE) regimen for relapsing TTP. On admission, the platelet (PLT) count was 95 × 109/L declining to 14 × 109/L in 5 days. Daily TPE was initiated for suspected TTP, and MMF was discontinued. A-IPC and PLT count were 1 × 109/L and 14 × 109/L, respectively, prior to first TPE. A-IPC improved to 3.2 × 109/L with 1 TPE, and on day 5, A-IPC and PLT count were 7.5 × 109/L and 218 × 109/L, respectively. On day 6, A-IPC and PLT count decreased to 4.8 × 109/L and 132 × 109/L further worsening to 0.4 × 109/L and 13 × 109/L, respectively. ADAMTS13 activity remained <5% with an inhibitor; counts did not recover. Initial improvement followed by rapidly declining A-IPC despite therapy suggested production suppression. In TTP, A-IPC may aid in establishing early therapy effects over PLT production.

Immature platelet dynamics correlate with ADAMTS13 deficiency and predict therapy response in immune-mediated thrombotic thrombocytopenic purpura.

INTRODUCTION: Thrombotic thrombocytopenic purpura (TTP) requires prompt initiation of therapeutic plasma exchange (TPE) to avoid significant morbidity and mortality. ADAMTS13 activity testing defines TTP, however, at most institutions this is a send-out test and therapy is often initiated prior to measurement availability. We describe our experience looking at absolute immature platelet counts (A-IPC) in patients suspected with TTP at presentation and in response to therapy. MATERIALS AND METHODS: Forty-eight patients treated for suspected TTP with A-IPC measure on admission and during hospitalization met inclusion criteria. Of these patients, sixteen had new-onset TTP (ADAMTS13 < 10%), ten were relapsing patients (first diagnosis prior to study period), and 22 were classified as non-TTP (ADAMTS13 ≥ 10%). RESULTS: Patients with ADAMTS13 deficiency (TTP) had A-IPC different from those without deficiency. A-IPC of 1-2 × 109/L at presentation had high sensitivity and specificity with a negative predictive value of 95.5 to 100%. Two-to-three-fold increases in A-IPC from count prior to TPE initiation was limited to ADAMTS13 deficient patients who was the group responding to therapy. Increases were higher in patients with new disease onset compared to relapsing patients (p = 0.018). Likewise, relapsing patients' A-IPC appeared dependent upon platelet count at time of relapse. A-IPC predicted and correlated with ADAMTS13 deficiency in new-onset TTP (p = 0.0002). CONCLUSIONS: Only patients with A-IPC-fold increases responded to TPE with platelet count normalization. Our results represent a proof of concept that A-IPC measurements can supplement ADAMTS13 testing and determine response to TPE. Future studies are needed to establish ways to apply these findings in the setting of suspected TTP.

Bacterial contamination and septic transfusion reaction rates associated with platelet components before and after introduction of primary culture: experience at a US Academic Medical Center 1991 through 2017.

BACKGROUND: The high incidence of septic transfusion reactions (STRs) led to testing being mandated by AABB from 2004. This was implemented by primary culture of single-donor apheresis platelets (APs) from 2004 and prestorage pooled platelets (PSPPs) from 2007. STUDY DESIGN/METHODS: Platelet (PLT) aliquots were cultured at issue and transfusion reactions evaluated at our hospital. Bacterial contamination and STR rates (shown as rates per million transfusions in Results) were evaluated before and after introduction of primary culture by blood centers that used a microbial detection system (BacT/ALERT, bioMerieux) or enhanced bacterial detection system (eBDS, Haemonetics). RESULTS: A total of 28,457 PLTs were cultured during pre-primary culture periods (44.7% APs; 55.3% at-issue pooled PLTs [AIPPs]) and 97,595 during post-primary culture periods (79.3% APs; 20.7% PSPPs). Forty-three contaminated units were identified in preculture and 34 in postculture periods (rates, 1511 vs. 348; p < 0.0001). Contamination rates of APs were significantly lower than AIPPs in the preculture (393 vs. 2415; p < 0.0001) but not postculture period compared to PSPPs (387 vs. 198; p = 0.9). STR rates (79 vs. 90; p = 0.98) were unchanged with APs but decreased considerably with pooled PLTs (826 vs. 50; p = 0.0006). Contamination (299 vs. 324; p = 0.84) and STR rates (25 vs. 116; p = 0.22) were similar for PLTs tested by BacT/ALERT and eBDS primary culture methods. A change in donor skin preparation method in 2012 was associated with decreased contamination and STR rates. CONCLUSION: Primary culture significantly reduced bacterial contamination and STR associated with pooled but not AP PLTs. Measures such as secondary testing near time of use or pathogen reduction are needed to further reduce STRs.

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.

Non-O blood group thrombotic thrombocytopenic purpura patients take longer to recover as measured by number of therapeutic plasma exchanges needed for platelet recovery.

INTRODUCTION: Therapeutic plasma exchange (TPE) is mainstay therapy for thrombotic thrombocytopenic purpura (TTP). However, it remains controversial if ABO type influences diagnosis or time to remission. MATERIALS AND METHODS: We investigated if ABO type influences length of TPE regimen in TTP patients with ADAMTS13 deficiency at our institution. Seventy out of 71 patients with suspected TTP who had ADAMTS13 activity measured were included. ADAMTS13 activity <10% defined those with idiopathic/acquired TTP (41/70). RESULTS: We found that among patients with ADAMTS13 deficiency, non-O patients required a significantly greater number of TPE (NoP) compared to O patients (p = 0.039). Additionally, patients with ADAMTS13 deficiency regardless of ABO type needed more TPE to achieve platelet recovery compared to those patients without deficiency (p = 0.00002). In regard to other variables that may affect response to therapy in TTP patients, we found no association between obesity and NoP; however, obesity rate was higher among ADAMTS13 deficient patients compared to overall obesity rate of our regional general population. Likewise, were found that blood group O did not occur with greater frequency in our cohort. CONCLUSIONS: Our data indicates that ABO may affect the NoP patients required for disease remission. We found that non-O patients needed more procedures to overcome their disease. Further work with greater number of patients will be needed to determine if specific non-O blood types require more procedures to recover their platelet count.

Alpha synuclein in hematopoiesis and immunity.

Parkinson's disease (PD) is the second most common neurodegenerative condition and intracellular deposition of Lewy bodies in the substantia nigra (SN), which can cause dopaminergic neuronal death, is the hallmark of this syndrome. α-synuclein (syn) is a small protein expressed mainly in neurons but can also be found in a number of tissues. It can be present as a soluble monomer under normal physiological conditions, but can be toxic in its oligomeric or fibrillary forms. Most of the available literature has focused on the effects of α-syn pathology in the mechanisms leading to PD. However, the normal functions of α-syn still remain to be fully elucidated. Notably, α-syn in the hematopoietic system seems to mediate important functions as indicated by anemia and incomplete cell maturation when this protein is absent. This review will summarize basic genetic and structural findings, and critical information that suggests an essential role of α-syn in the development and activation of the hematopoietic system and immunity.