Anne M. Winkler

Initiation and Regulation of Complement during Hemolytic Transfusion Reactions

Hemolytic transfusion reactions represent one of the most common causes of transfusion-related mortality. Although many factors influence hemolytic transfusion reactions, complement activation represents one of the most common features associated with fatality. In this paper we will focus on the role of complement in initiating and regulating hemolytic transfusion reactions and will discuss potential strategies aimed at mitigating or favorably modulating complement during incompatible red blood cell transfusions.

Integrating Molecular Technologies for Red Blood Cell Typing and Compatibility Testing Into Blood Centers and Transfusion Services

Nucleic acid-based technology is now at a point where the field of transfusion medicine is ready for its widespread application. In the donor center, genotyping of red blood cell (RBC) products provides phenotype-matched products for special patient populations or antigen-negative products for patients with alloantibodies. In the immunohematology reference laboratory, molecular technologies aid in discerning blood types in the situation of a typing discrepancy and improve pretransfusion RBC testing reagents. In the hospital transfusion service, genotyping patients aids in providing phenotype-matched RBC products. In prenatal testing, genotyping for RHD aids in the decision for Rh immune globulin prophylaxis and predicting risk of hemolytic disease of the fetus and newborn. Before genotyping is accepted as the universal standard for pretransfusion and donor testing, important limitations of this technology must be addressed, including the fact that the genotype does not always predict the phenotype and the need for creating the ideal high-throughput platform. Clinical trials are needed to answer important questions, and a donor and patient database is needed. A stepwise plan for progressive introduction into the donor centers and transfusion services must be established. In conclusion, the field of transfusion medicine is ready to expand the use of molecular diagnostics.

Pathophysiology of Early Trauma Induced Coagulopathy: Emerging Evidence for Hemodilution and Coagulation Factor Depletion

BACKGROUND Trauma patients present with a coagulopathy, termed early trauma-induced coagulopathy (ETIC), that is associated with increased mortality. This study investigated hemostatic changes responsible for ETIC. METHODS Case-control study of trauma patients with and without ETIC, defined as prolonged prothrombin time (PT), was performed from prospective cohort of consecutive trauma patients who presented to Level I trauma center. Univariate and multivariate analyses were performed. RESULTS The case-control study group (n = 91) was 80% male, with mean age of 37 years, 17% penetrating trauma and 7% mortality rate. Patients with ETIC demonstrated decreased common and extrinsic pathway factor activities (factors V and VII) and decreased inhibition of the coagulation cascade (antithrombin and protein C activities) when compared with the matched control patients without ETIC. Both cohorts had evidence of increased thrombin and fibrin generation (prothrombin fragment 1.2 levels, thrombin-antithrombin complexes, and soluble fibrin monomer), increased fibrinolysis (d-dimer levels), and increased inhibition of fibrinolysis (plasminogen activator inhibitor-1 activity) above normal reference values. Patients with versus without ETIC had increased mortality and received increased amount of blood products. CONCLUSION ETIC following injury is associated with decreased factor activities without significant differences in thrombin and fibrin generation, suggesting that despite these perturbations in the coagulation cascade, patients displayed a balanced hemostatic response to injury. The lower factor activities are likely secondary to increased hemodilution and coagulation factor depletion. Thus, decreasing the amount of crystalloid infused in the early phases following trauma and administration of coagulation factors may prevent the development.

Laboratory test support for Ebola patients within a high-containment facility.

Two adult United States (US) nationals contracted the Ebola virus while on a humanitarian mission in Africa amidst a large Ebola outbreak there. They were admitted to our medical center (Emory University Hospital in Atlanta, GA) during the first week of August 2014 for treatment. Both survived their illness and were released after approximately 3 weeks of inpatient care. We received approximately 3 days’ advance notice that the first patient would be transported from Africa to our medical center; the second patient arrived 3 days after the first. The diagnosis in each case had been confirmed virologically by detecting Ebola-specific nucleic acid in blood specimens sent to a World Health Organization laboratory in Europe; however, few details of either patient’s condition had been available to us before their arrival. Herein, we summarize the approach we used to plan for and provide laboratory diagnostic testing during their treatment. Both patients were admitted to a specialized isolation unit that had been established at our hospital 12 years previously, in collaboration with the Centers for Disease Control and Prevention (CDC), as a resource for safely quarantining, evaluating, and caring for small numbers of patients with unidentified or highly contagious infectious diseases. At the core of this unit are 3 patient rooms that are physically separate from other patient-care areas of the hospital, are maintained under negative air pressure, and have highly restricted access. A small, specially trained team of volunteer caregivers (primarily infectious disease physicians and critical care nurses) who have planned and rehearsed for incidents of this type for more than a decade staffs the facility. The degree of containment afforded by this facility substantially exceeds CDC guidelines for managing Ebola,1 a nonairborne …

Impact of red blood cell alloimmunization on sickle cell disease mortality: a case series.

Although red blood cell (RBC) transfusion represents an integral component of sickle cell disease (SCD) care, transfusion support for some patients can result in alloimmunization to RBC antigens. Alloimmunized patients with SCD appear to experience worse survival compared to nonalloimmunized patients. While this difference in mortality may in part be due to underlying immunologic differences related to disease severity, it may also reflect direct clinical consequences of RBC alloimmunization. Alloimmunized patients have an increased risk of serious hemolytic transfusion reactions (HTRs) and may not receive adequate RBC transfusion support due to lack of compatible RBC units.

Effect of antiplatelet therapy and platelet function testing on hemorrhagic and thrombotic complications in patients with cerebral aneurysms treated with the pipeline embolization device: a review and meta-analysis.

Purpose The pipeline embolization device (PED) necessitates dual antiplatelet therapy (APT) to decrease thrombotic complications while possibly increasing bleeding risks. The role of APT dose, duration, and response in patients with hemorrhagic and thromboembolic events warrants further analysis. Methods A PubMed and Google Scholar search from 2009 to 2014 was performed using the following search terms individually or in combination: pipeline embolization device, aneurysm(s), and flow diversion, excluding other flow diverters. Review of the bibliographies of the retrieved articles yielded 19 single and multicenter studies. A statistical meta-analysis between aspirin (ASA) dose (low dose ≤160 mg, high dose ≥300 mg), loading doses of APT agents, post-PED APT regimens, and platelet function testing (PFT) with hemorrhagic or thrombotic complications was performed. Results ASA therapy for ≤6 months post-PED was associated with increased hemorrhagic events. High dose ASA ≤6 months post-PED was associated with fewer thrombotic events compared with low dose ASA. Post-PED clopidogrel for ≤6 months demonstrated an increased incidence of symptomatic thrombotic events. Loading doses of ASA plus clopidogrel demonstrated a decreased incidence of permanent symptomatic hemorrhagic events. PFT did not show a statistically significant relationship with symptomatic hemorrhagic or thrombotic complications. Conclusions High dose ASA >6 months is associated with fewer permanent thrombotic and hemorrhagic events. Clopidogrel therapy ≤6 months is associated with higher rates of thrombotic events. Loading doses of ASA and clopidogrel were associated with a decreased incidence of hemorrhagic events. PFT did not have any significant association with symptomatic events.

A diagnosis of heparin-induced thrombocytopenia with combined clinical and laboratory methods in cardiothoracic surgical intensive care unit patients.

BACKGROUND:Diagnosing postoperative heparin-induced thrombocytopenia (HIT) in cardiothoracic surgical patients is complicated because of the profound thrombocytopenia that occurs with cardiopulmonary bypass (CPB). CPB predisposes patients to develop a frequent incidence of antibodies directed against platelet factor 4 (PF4)/heparin complexes and HIT. The sensitivity of readily available antibody immunoassays is high, but specificity is quite low. The use of both a clinical probability score and rapid laboratory immunoassay has been shown to increase specificity, which is of particular importance in the CPB setting. Prompt diagnosis is crucial because cessation of heparin and treatment with alternative anticoagulation can reduce the risk of thromboembolic events. METHODS:We retrospectively reviewed records from cardiothoracic surgical patients whose serum was tested with both the serotonin release assay (SRA) and the PF4/heparin immunoassay from January 2007 through December 2010. We assigned a high, intermediate, or low clinical “4Ts” probability score that quantifies thrombocytopenia, timing of platelet decrease, and thrombotic complications in each patient. We then compared the clinical score and the PF4/heparin immunoassay against the “gold standard” diagnostic test, the SRA. RESULTS:The sensitivity and specificity for PF4/heparin optical density >0.40 were 100% and 26%, respectively. Sensitivity and specificity for the diagnosis of HIT with a combination of PF4/heparin optical density >0.40 and high/intermediate 4Ts score were 100% and 70%, respectively. The negative predictive value was 100% for low 4Ts score. CONCLUSIONS:We demonstrated that the use of the 4Ts clinical score combined with the PF4/heparin immunoassay for HIT diagnosis increases the sensitivity and specificity of HIT testing compared with the PF4/heparin immunoassay alone. Furthermore, with an intermediate 4Ts score and positive PF4/heparin antibody test, a confirmatory platelet activation assay such as the SRA is necessary. Physicians treating patients after cardiothoracic surgery should recognize the need for an antibody test and confirmation with a platelet activation assay with even moderate clinical probability of HIT.

Clinical Use of the Activated Partial Thromboplastin Time and Prothrombin Time for Screening: A Review of the Literature and Current Guidelines for Testing

Although the activated partial thromboplastin time, prothrombin time, and international normalized ratio are widely used in routine preoperative testing, these hemostatic tests are not reliable predictors of perioperative bleeding in patients without known bleeding risk factors. In contrast, a preoperative bleeding history and physical examination are usually obtained in an attempt to identify important bleeding risk factors. However, these coagulation tests are used extensively for monitoring anticoagulation with different pharmacologic agents.

Heparin-induced thrombocytopenia and cardiac surgery.

Purpose of review Heparin-induced thrombocytopenia (HIT) is an important, increasingly recognized antibody-mediated complication of heparin therapy occurring in approximately 0.5–5% of patients receiving heparin for at least 5 days. HIT is a prothrombotic disorder that typically presents with a 50% platelet count drop, thrombotic event manifesting usually 5–14 days after starting heparin, or both. HIT antibodies usually decrease to negative titers/levels within 3 months. When there is clinical suspicion of HIT, heparin should be discontinued and alternative anticoagulation should be considered, as well as laboratory evaluation for HIT. Recent findings HIT immunoassay results should be used for clinical decision-making about initial anticoagulation management. Recent data reevaluate the importance of absolute titers of HIT antibodies as a risk factor for clinical occurrence. Although laboratory assays are routinely used, current data suggest that increasing optical densities are more likely associated with a positive 14C-serotonin release assay and HIT. HIT is also associated with a greater risk for adverse events, so even though alternative anticoagulation is used, clinicians should be aware of this hypercoagulable syndrome. Summary For patients with HIT, alternative anticoagulation is available, but for cardiovascular surgery, if the operation cannot be delayed until HIT antibodies have become negative, alternative anticoagulation strategies are recommended, although patients with HIT are at a greater risk for adverse outcomes.

Immunophenotypic parameters and RBC alloimmunization in children with sickle cell disease on chronic transfusion

Alloimmunization against red blood cell (RBC) antigens is a cause of morbidity and mortality in transfused patients with sickle cell disease (SCD). To investigate distinguishing characteristics of patients who develop RBC alloantibodies after transfusion (responders) versus those who do not (non‐responders), a cross‐sectional study of 90 children with SCD on chronic RBC transfusion therapy at a single institution was conducted in which 18 immune parameters (including T and B cell subsets) were tested via flow cytometry, and medical records were reviewed. RBC alloimmunization was present in 26/90 (29%) patients, with anti‐E, K, and C among the most commonly detected alloantibodies despite prophylactic matching for these antigens at the study institution. In addition, RBC autoantibodies had been detected in 18/26 (69%) of alloimmunized versus 7/64 (11%) of non‐alloimmunized patients (P < 0.0001). Alloimmunized patients were significantly older (median 13.0 years vs. 10.7 years, P = 0.010) and had more RBC unit exposures (median 148 U vs. 82 U, P = 0.020) than non‐alloimmunized patients. Sex, age at initiation of chronic transfusion, splenectomy, stroke, and transfusion outside of the study institution were not significantly associated with RBC alloimmunization. Alloimmunized patients had a significantly increased percentage of CD4+ T memory cells compared to non‐alloimmunized patients (57% vs. 49%, P = 0.0047), with no other significant differences in immune cell subsets or laboratory values detected between these groups. Additional research of RBC alloimmunization is needed to optimize transfusion therapy and to develop strategies to prevent alloimmunization. Am. J. Hematol. 90:1135–1141, 2015.