Alexander Duncan

Dengue virus–induced hemorrhage in a nonhuman primate model

Lack of a dengue hemorrhagic animal model recapitulating human dengue virus infection has been a significant impediment in advancing our understanding of the early events involved in the pathogenesis of dengue disease. In efforts to address this issue, a group of rhesus macaques were intravenously infected with dengue virus serotype 2 (strain 16 681) at 1 x 10(7) PFU/animal. A classic dengue hemorrhage developed 3 to 5 days after infection in 6 of 6 animals. Blood chemistry appeared to be normal with exception of creatine phosphokinase, which peaked at 7 days after infection. A modest thrombocytopenia and noticeable neutropenia concomitant with slight decrease of hemoglobin and hematocrit were registered. In addition, the concentration of D-dimer was elevated significantly. Viremia peaked at 3 to 5 days after infection followed by an inverse relationship between T and B lymphocytes and a bimodal pattern for platelet-monocytes and platelet-neutrophil aggregates. Dengue virus containing platelets engulfed by monocytes was noted at 8 or 9 days after infection. Thus, rhesus macaques inoculated intravenously with a high dose of dengue virus produced dengue hemorrhage, which may provide a unique platform to define the early events in dengue virus infection and help identify which blood components contribute to the pathogenesis of dengue disease.

Antithrombin deficiency: Issues in laboratory diagnosis

OBJECTIVE To review the current understanding of the pathophysiology of antithrombin deficiency and its role in congenital thrombophilia. Recommendations for diagnostic testing of antithrombin function and concentration, derived from the medical literature and consensus opinions of recognized experts in the field, are included. These recommendations specify whom, how, and when to test. DATA SOURCES Review of the published medical literature. DATA EXTRACTION AND SYNTHESIS A summary of the medical literature and proposed testing recommendations were prepared and presented at the College of American Pathologists Conference XXXVI: Diagnostic Issues in Thrombophilia. After discussion at the conference, consensus recommendations presented in this article were accepted after a two-thirds majority vote by the participants. CONCLUSIONS Antithrombin deficiency is an infrequent genetic abnormality that may be a significant contributing cause of thrombophilia. Antithrombin deficiency also may be observed in conjunction with other genetic or acquired risk factors. Assay of antithrombin plasma levels is appropriate in the laboratory evaluation of individuals with thrombophilia, preferably using a functional, amidolytic antithrombin assay. The diagnosis of antithrombin deficiency should be established only after other acquired causes of antithrombin deficiency, such as liver disease, consumptive coagulopathy, or heparin therapy, are excluded. A low antithrombin level should be confirmed with a subsequent assay on a fresh specimen, and family studies may be helpful to establish the diagnosis. Antigenic antithrombin assays may be of benefit in subclassification of the type of antithrombin deficiency and to confirm the decreased antithrombin level in patients with type I deficiency.

Successful ABO-incompatible pediatric liver transplantation utilizing standard immunosuppression with selective postoperative plasmapheresis

Transplanting blood group A, B, or O (ABO)‐incompatible (ABO‐I) liver grafts has resulted in lower patient and graft survival with an increased incidence of vascular and biliary complications and rejection. We report that, without modification of our standard immunosuppression protocol, crossing blood groups is an acceptable option for children requiring liver transplantation. In our study, ABO‐I liver grafts—regardless of recipient age—have comparable long‐term survival (mean follow‐up of 3.25 yr) with ABO‐compatible grafts without any difference in rejection, vascular or biliary complications. From January 1, 1999 to October 1, 2005, we studied 138 liver transplants in 121 children: 16 (13.2%) received an ABO incompatible liver allograft. One‐year actuarial patient survival for ABO‐matched grafts vs. ABO‐I grafts was 93.0% and 100%, respectively, whereas graft survival was 83.4% and 92.3%. Additionally, 6 of 16 (37.5%) ABO‐I transplanted children had 8 rejection episodes, whereas 47 patients (44.8%) had 121 rejection episodes in the ABO‐compatible group. There were no vascular complications and 2 biliary strictures in the ABO‐I group. Plasmapheresis was not used for pretransplantation desensitization and was only required in 1 posttransplantation recipient. No child was splenectomized. Six of the 16 children were older than 13 yr of age, suggesting the possibility of successfully expanding this technique to an older population. In conclusion, our outcomes may support the concept of using ABO‐I grafts in a more elective setting associated with split and living donor liver transplants. Liver Transpl 12:972–978, 2006.

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 …

Malignant angioendotheliomatosis presenting as disseminated intravascular coagulopathy

Disseminated intravascular coagulopathy (DIC) occurred in a patient with hemolytic anemia and anasarca. Skin and muscle biopsy showed intravascular lymphomatosis (malignant angioendotheliomatosis). Combination chemotherapy resulted in resolution of the DIC and anasarca. After an unmaintained 8‐month clinical remission, the patient had central nervous system relapse and died. Malignant angioendotheliomatosis is a rare disorder that should be considered among the occult causes of DIC. Cancer 68:2319–2323, 1991.

Overview of Pharmacogenetics in Anticoagulation Therapy

Although used for many years, a detailed understanding of the mechanism of action and metabolism of anticoagulants has become available only recently. After the addition of pharmacogenetic data to the drug label by the U.S. Food and Drug Administration, interest in the pharmacogenetics of warfarin and its clinical application has grown exponentially. Dosing algorithms have been developed and continue to be refined that incorporate the polymorphisms of P450 2C9 and vitamin K epoxide reductase. Widespread adoption of these algorithms has been slow because of factors such as physician education, timely testing, complexity of dosing calculations, dietary variations, and other confounding variables. Although most useful before the first dose, these tests are also being used to explain labile responses to warfarin. Current protocols are capable of predicting a large portion of interindividual dosing variation and, as more data become available, truly personalized dosing of warfarin should be achievable, improving patient safety and clinical efficacy.

Effects of storage duration and volume on the quality of leukoreduced apheresis-derived platelets: implications for pediatric transfusion medicine

BACKGROUND: Platelet (PLT) storage adversely affects PLT structure and function in vitro and is associated with decreased PLT recovery and function in vivo. In pediatric transfusion medicine, it is not uncommon for small residual volumes to remain in parent units after aliquot preparation of leukoreduced apheresis‐derived PLTs (LR‐ADP). However, limited data exist regarding the impact of storage on residual small‐volume LR‐ADP.

Chemotherapy-induced hemolytic uremic syndrome: description of a potential animal model.

Hemolytic uremic syndrome (HUS) is an uncommon complication of chemotherapy that contributes to the morbidity of oncology and bone marrow transplant patients. The pathogenesis is not well understood and no established clinical animal model exists. We studied four rhesus monkeys (RM) that developed fatal HUS following high‐dose chemotherapy. Microangiopathic hemolytic anemia (pre‐Hct 40% and day 5–8 Hct 31 % (P <.05), increased BUN (168 mg/dl), creatinine (8.2 mg/dl), and lactate dehydrogenase (1458 IU/L) (mean day 5–8 measurements) were observed. Platelets counts decreased to 39±15 × 109/l from a mean of 397±31 × 109/L (P < .0001). vWF, ATIII, thrombin:anti‐thrombin complex (T:AT) and prothrombin fragment F1.2 levels were not different from a control group (N = 2). The data presented describe chemotherapy‐induced HUS with typical clinical and laboratory features which may provide an animal model for the study of this important syndrome.

Is the Incidence of Heparin-Induced Thrombocytopenia Affected by the Increased Use of Heparin for VTE Prophylaxis?

BACKGROUND The increased exposure to heparin products for thromboprophylaxis against VTE in hospitalized patients raises concerns for an increase in the incidence of heparin-induced thrombocytopenia(HIT). METHODS We analyzed, among 90,875 patients exposed to heparin products between 2005 and 2009, the number of hematologic consultations for thrombocytopenia, requests for heparin induced antibodies by enzyme-linked immunosorbent assay, and cases given a diagnosis of HIT by the hematology consult service. RESULTS We observed that despite a doubling in the number of patients receiving pharmacoprophylaxis with heparin, there was no significant increase in the number of consultations for thrombocytopenia,the number of requests for HIT tests, the number of positive HIT test results, or the number of HIT diagnoses. The number of cases of HIT was low and represented < 0.1% of patients exposed to heparin. CONCLUSIONS We conclude that concerns about HIT should not be a limiting factor for the systematic implementation of heparin-based VTE prophylaxis.

Laboratory Quality Control For All Can This Be Achieved

Visiting hospitals in Africa and meeting with clinicians, pathologists, and laboratory directors, it rapidly becomes apparent that confidence in any diagnostic services is lacking. Clinicians cite many reasons. Some days complete blood cell counts and chemistries are available, while on other days, because there are no reagents available, physicians have no results to guide treatment for their patients. Blood cultures, when available, are frequently contaminated by fungi and bacteria and you cannot be sure if the organism identified is the cause of the patients fever. Turnaround times are incredibly long, and by the time a result is available, it is too late to be clinically relevant. Consequently, clinicians continue to practice medicine using a syndromic approach rather than defining a specific diagnosis. Unfortunately, this happens routinely, even in large African academic centers and in much of the developing world. One of the things that clinicians in developed countries take for granted are efficient laboratories that deliver credible results. For example, clinicians order blood work as the patient is leaving their office, and the results appear in the electronic medical record that afternoon. They get a call from the laboratory when budding yeasts show up in a blood culture obtained 2 days ago in a patient with a transplant who had been admitted with fever and treat the patient accordingly; they know blood culture contamination rates in the hospital are low and are confident that there is little likelihood that these yeasts are a contaminant. Two days after a patient with a gastric ulcer undergoes an endoscopic biopsy, a pathologists report shows adenocarcinoma, and thus staging and treatment can be started. Having reagents daily in the laboratory and working with well-maintained instruments allow for dependable turnaround times. Using internal and external quality controls is indispensable for consistency of laboratory results. These …