Cancer-associated venous thromboembolism: Incidence and features in a racially diverse population

BACKGROUND

Data on the population-based incidence of cancer-associated venous thromboembolism (VTE) from racially diverse populations are limited.

OBJECTIVE

To evaluate the incidence and burden of cancer-associated VTE, including demographic and racial subgroups in the general population of Oklahoma County-which closely mirrors the United States.

DESIGN

A population-based prospective study.

SETTING

We conducted surveillance of VTE at tertiary care facilities and outpatient clinics in Oklahoma County, Oklahoma, from 2012-2014. Surveillance included reviewing all imaging reports used to diagnose VTE and identifying VTE events from hospital discharge data and death certificates. Cancer status was determined by linkage to the Oklahoma Central Cancer Registry.

MEASUREMENTS

We used Poisson regression to calculate crude and age-adjusted incidence rates of cancer-associated VTE per 100 000 general population per year, with 95% confidence intervals (95% CI).

RESULTS

The age-adjusted incidence (95% CI) of cancer-associated VTE among adults age ≥ 18 was 70.0 (65.1-75.3). The age-adjusted incidence rates (95% CI) were 85.9 (72.7-101.6) for non-Hispanic Blacks, 79.5 (13.2-86.5) for non-Hispanic Whites, 18.8 (8.9-39.4) for Native Americans, 15.6 (7.0-34.8) for Asian/Pacific Islanders, and 15.2 (9.2-25.1) for Hispanics. Recurrent VTE up to 2 years after the initial diagnosis occurred in 38 of 304 patients (12.5%) with active cancer and in 34 of 424 patients (8.0%) with a history of cancer > 6 months previously.

CONCLUSION

Age-adjusted incidence rates of cancer-associated VTE vary substantially by race and ethnicity. The relatively high incidence rates of first VTE and of recurrence warrant further assessment of strategies to prevent VTE among cancer patients.

Incidence of Venous Thromboembolism in a Racially Diverse Population of Oklahoma County, Oklahoma

Background  Contemporary incidence data for venous thromboembolism (VTE) from racially diverse populations are limited. The racial distribution of Oklahoma County closely mirrors that of the United States.

Objective  To evaluate VTE incidence and mortality, including demographic and racial subgroups.

Design  Population-based prospective study.

Setting  We conducted VTE surveillance at all relevant tertiary care facilities and outpatient clinics in Oklahoma County, Oklahoma during 2012 to 2014, using both active and passive methods. Active surveillance involved reviewing all imaging reports used to diagnose VTE. Passive surveillance entailed identifying VTE events from hospital discharge data and death certificate records.

Measurements  We used Poisson regression to calculate crude, age-stratified, and age-adjusted incidence and mortality rates per 1,000 population per year and 95% confidence intervals (CIs).

Results  The incidence rate of all VTE was 3.02 (2.92–3.12) for those age ≥18 years and 0.05 (0.04–0.08) for those <18 years. The age-adjusted incidence rates of all VTE, deep vein thrombosis, and pulmonary embolism were 2.47 (95% CI: 2.39–2.55), 1.47 (1.41–1.54), and 0.99 (0.93–1.04), respectively. The age-adjusted VTE incidence and the 30-day mortality rates, respectively, were 0.63 and 0.121 for Asians/Pacific Islanders, 3.25 and 0.355 for blacks, 0.67 and 0.111 for Hispanics, 1.25 and 0.195 for Native Americans, and 2.71 and 0.396 for whites.

Conclusion  The age-adjusted VTE incidence and mortality rates vary substantially by race. The incidence of three per 1,000 adults per year indicates an important disease burden, and is informative of the burden in the U.S. population.

Incidence and characteristics of cancer-associated thrombosis in a racially diverse population: A population-based study

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Background: Venous thromboembolism (VTE) is a common complication in cancer patients, but contemporary data on the incidence and characteristics of cancer-associated VTE in different racial populations is limited. We sought to measure the incidence rate and characteristics of cancer-associated VTE in a racially diverse population. Methods: We performed a prospective, population–based cohort study of VTE in Oklahoma County, OK during April 1, 2012–March 31, 2014. Surveillance staff regularly visited all tertiary care and relevant outpatient facilities in the county and reviewed the text from all imaging results of chest computed tomography or magnetic resonance imaging, lung perfusion scans, and ultrasound of the extremities to identify cases of VTE. Data on patient characteristics were collected from the electronic medical record. VTE was considered cancer-associated if the patient had a history of cancer other than basal or squamous cell skin cancer. Cancer was defined as “active” if metastatic or diagnosed within 6 months prior to VTE. Associations and incidence were calculated using the chi-square test and Poisson regression, respectively. Results: Of 3,255 patients with ≥1 VTE event (deep-vein thrombosis and/or pulmonary embolism), 732 (23%) had a history of cancer, of whom 309 had active cancer. The types of cancer varied widely. The age-adjusted incidence of cancer-associated VTE was 648 per 100,000 adult population (age ≥ 18). Incidence increased with each decade of age. The racial/ethnic-specific incidence rates were as follows (each per 100,000): Whites non-hispanic (607), Blacks non-Hispanic (557), Native Americans (128), Asian/Pacific Islanders (113) and Hispanics (70). Risk factors for VTE among the 732 with cancer-associated VTE included previous VTE (19%), hospitalization (37%), surgery (33%), and central venous catheter (22%). Of those with a history of cancer ≥ 6 months previously, 32% had no other identifiable VTE risk factor. Conclusions: Cancer-associated VTE comprised about 20-25% of the total population burden of VTE. The incidence varied substantially by race/ethnicity. An appreciable proportion of those with a history of cancer ≥ 6 months previously subsequently developed VTE in the absence of other risk factors.

Risk of venous thromboembolism among hospitalizations of adults with selected autoimmune diseases

Previous research has suggested autoimmune diseases are risk factors for developing venous thromboembolism (VTE). We assessed whether having diagnoses of selected autoimmune diseases associated with antiphospholipid antibodies--autoimmune hemolytic anemia (AIHA), immune thrombocytopenic purpura (ITP), rheumatoid arthritis (RA), and systemic lupus erythematosus (SLE)--were associated with having a VTE diagnosis among US adult hospitalizations. A cross-sectional study was conducted using the 2010 Nationwide Inpatient Sample of the Healthcare Cost and Utilization Project, Agency for Healthcare Research and Quality. VTE and autoimmune diseases were identified using International Classification of Diseases, Ninth Revision, Clinical Modification coded diagnoses information. The percentages of hospitalizations with a VTE diagnosis among all non-maternal adult hospitalizations without any of the four autoimmune diseases of interest and among those with AIHA, ITP, RA, and SLE diagnoses were 2.28, 4.46, 3.35, 2.65 and 2.77%, respectively. The adjusted odds ratios (OR) for having a diagnosis of VTE among non-maternal adult hospitalizations with diagnoses of AIHA, ITP, RA, and SLE were 1.25 [95% confidence interval (CI) 1.05-1.49], 1.20 (95% CI 1.07-1.34), 1.17 (95% CI 1.13-1.21), and 1.23 (95% CI 1.15-1.32), respectively, when compared to those without the corresponding conditions. The adjusted OR for a diagnosis of VTE associated with a diagnosis of any of the four autoimmune diseases was 1.20 (95% CI 1.16-1.24). The presence of a diagnosis of AIHA, ITP, RA, and SLE was associated with an increased likelihood of having a VTE diagnosis among the group of all non-maternal adult hospitalizations.

Determinants of venous thromboembolism among hospitalizations of US adults: a multilevel analysis

Background

Venous thromboembolism (VTE) is a significant clinical and public health concern. We evaluated a variety of multilevel factors—demographics, clinical and insurance status, preexisting comorbid conditions, and hospital characteristics—for VTE diagnosis among hospitalizations of US adults.

Methods

We generated adjusted odds ratios with 95% confidence intervals (CIs) and determined sources of outcome variation by conducting multilevel logistic regression analysis of data from the 2011 Nationwide Inpatient Sample that included 6,710,066 hospitalizations of US adults nested within 1,039 hospitals.

Results

Among hospitalizations of adults, age, sex, race or ethnicity, total days of hospital stay, status of health insurance, and operating room procedure were important determinants of VTE diagnosis; each of the following preexisting comorbid conditions—acquired immune deficiency syndrome, anemia, arthritis, congestive heart failure, coagulopathy, hypertension, lymphoma, metastatic cancer, other neurological disorders, obesity, paralysis, pulmonary circulation disorders, renal failure, solid tumor without metastasis, and weight loss—was associated independently with 1.04 (95% CI: 1.02−1.06) to 2.91 (95% CI: 2.81−3.00) times increased likelihood of VTE diagnosis than among hospitalizations of adults without any of these corresponding conditions. The presence of 2 or more of such conditions was associated a 180%−450% increased likelihood of a VTE diagnosis. Hospitalizations of adults who were treated in urban hospitals were associated with a 14%−15% increased likelihood of having a VTE diagnosis than those treated in rural hospitals. Approximately 7.4% of the total variation in VTE diagnosis occurred between hospitals.

Conclusion

The presence of certain comorbidities and hospital contextual factors is associated with significantly elevated likelihood of VTE diagnosis among hospitalizations of adults. The findings of this study underscore the importance of clinical risk assessment and adherence to evidence-based clinical practice guidelines in preventing VTE, as well as the need to evaluate potential contextual factors that might modify the risk of VTE among hospitalized patients.

Whole blood gene expression profiles distinguish clinical phenotypes of venous thromboembolism

INTRODUCTION

Recurrent venous thromboembolism (VTE) occurs infrequently following a provoked event but occurs in up to 30% of individuals following an initial unprovoked event. There is limited understanding of the biological mechanisms that predispose patients to recurrent VTE.

OBJECTIVES

To identify whole blood gene expression profiles that distinguished patients with clinically distinct patterns of VTE.

PATIENTS/METHODS

We studied 107 patients with VTE separated into 3 groups: (1) 'low-risk' patients had one or more provoked VTE; (2) 'moderate-risk' patients had a single unprovoked VTE; (3) 'high-risk' patients had ≥2 unprovoked VTE. Each patient group was also compared to twenty-five individuals with no personal history of VTE. Total RNA from whole blood was isolated and hybridized to Illumina HT-12V4 Beadchips to assay whole genome expression.

RESULTS

Using class prediction analysis, we distinguished high-risk patients from low-risk patients and healthy controls with good receiver operating curve characteristics (AUC=0.81 and 0.84, respectively). We also distinguished moderate-risk individuals and low-risk individuals from healthy controls with AUC's of 0.69 and 0.80, respectively. Using differential expression analysis, we identified several genes previously implicated in thrombotic disorders by genetic analyses, including SELP, KLKB1, ANXA5, and CD46. Protein levels for several of the identified genes were not significantly different between the different groups.

CONCLUSION

Gene expression profiles are capable of distinguishing patients with different clinical presentations of VTE, and genes relevant to VTE risk are frequently differentially expressed in these comparisons.

Public health surveillance of nonmalignant blood disorders

Nonmalignant blood disorders currently affect millions of Americans, and their prevalence is expected to grow over the next several decades. This is owing to improvements in treatment leading to increased life expectancy of people with hereditary conditions, like sickle cell disease and hemophilia, but also the rising occurrence of risk factors for venous thromboembolism. The lack of adequate surveillance systems to monitor these conditions and their associated health indicators is a significant barrier to successfully assess, inform, and measure prevention efforts and progress toward national health goals. CDC is strengthening surveillance activities for blood disorders by improving and developing new methods that are tailored to best capture and monitor the epidemiologic characteristics unique to each disorder. These activities will provide a robust evidence base for public health action to improve the health of patients affected by or at risk for these disorders.

Differences in thrombotic risk factors in black and white women with adverse pregnancy outcome

INTRODUCTION

Black women have an increased risk of adverse pregnancy outcomes and the characteristics of thrombotic risk factors in this population are unknown. The objective of this study was to examine the racial differences in thrombotic risk factors among women with adverse pregnancy outcomes.

METHODS

Uniform data were collected in women with adverse pregnancy outcomes (pregnancy losses, intrauterine growth restriction (IUGR), prematurity, placental abruption and preeclampsia) referred to Thrombosis Network Centers funded by the Centers for Disease Control and Prevention (CDC).

RESULTS

Among 343 white and 66 black women seen for adverse pregnancy outcomes, protein S and antithrombin deficiencies were more common in black women. The prevalence of diagnosed thrombophilia was higher among whites compared to blacks largely due to Factor V Leiden mutation. The prevalence of a personal history of venous thromboembolism (VTE) did not differ significantly by race. A family history of VTE, thrombophilia, and stroke or myocardial infarction (MI) was higher among whites. Black women had a higher body mass index, and a higher prevalence of hypertension, while the prevalence of sickle cell disease was approximately 27 fold higher compared to the general US black population.

CONCLUSIONS

Thrombotic risk factors differ significantly in white and black women with adverse pregnancy outcomes. Such differences highlight the importance of considering race separately when assessing thrombotic risk factors for adverse pregnancy outcomes.

Predictive accuracy of 29-comorbidity index for in-hospital deaths in US adult hospitalizations with a diagnosis of venous thromboembolism

Background

Venous thromboembolism (VTE), comprising deep vein thrombosis (DVT) and pulmonary embolism (PE), is a significant source of mortality and morbidity worldwide. By analyzing data of the 2010 Nationwide Inpatient Sample from the Agency for Healthcare Research and Quality (AHRQ), we evaluated the predictive accuracy of the AHRQ’s 29-comorbidity index with in-hospital death among US adult hospitalizations with a diagnosis of VTE.

Methods

We assessed the case-fatality and prevalence of comorbidities among a sample of 153,518 adult hospitalizations with a diagnosis of VTE that comprised 87,605 DVTs and 65,913 PEs (with and without DVT). We estimated adjusted odds ratios and 95% confidence intervals with multivariable logistic regression models by using comorbidities as predictors and status of in-hospital death as an outcome variable. We assessed the c-statistics for the predictive accuracy of the logistic regression models.

Results

In 2010, approximately 41,944 in-hospital deaths (20,212 with DVT and 21,732 with PE) occurred among 770,137 hospitalizations with a diagnosis of VTE. When compared separately to hospitalizations with VTE, DVT, or PE that had no corresponding comorbidities, congestive heart failure, chronic pulmonary disease, coagulopathy, liver disease, lymphoma, fluid and electrolyte disorders, metastatic cancer, other neurological disorders, peripheral vascular disorders, pulmonary circulation disorders, renal failure, solid tumor without metastasis, and weight loss were positively and independently associated with 10%−125% increased likelihoods of in-hospital death. The c-statistic values ranged from 0.776 to 0.802.

Conclusion

The results of this study indicated that comorbidity was associated independently with risk of death among hospitalizations with VTE and among hospitalizations with DVT or PE. The AHRQ 29-comorbidity index provides acceptable to excellent predictive accuracy for in-hospital deaths among adult hospitalizations with VTE and among those with DVT or PE.

Characteristics of abdominal vein thrombosis in children and adults

The demographic and clinical characteristics of adults and children with lower extremity deep-vein thrombosis and/or pulmonary embolism (LE DVT/PE) may differ from those with abdominal vein thrombosis (abdominal VT). Abdominal VT can be a presenting sign of an underlying prothrombotic state, and its presence in the setting of known disease might have prognostic implications different from LE DVT/PE. This study describes clinical presentations of abdominal VT compared to LE DVT/PE in adults and children. We analysed prospectively-collected data from consecutive consenting patients enrolled in one of seven Centers for Disease Control and Prevention (CDC) funded Thrombosis and Hemostasis Network Centers from August 2003 to April 2011 to compare the demographic and clinical characteristics of adults and children with abdominal VT. Both adults and children with abdominal VT tended to be younger and have a lower body mass index (BMI) than those with LE DVT/PE. Of patients with abdominal VT, children were more likely to have inferior vena cava (IVC) thrombosis than adults. For adults with venous thromboembolism (VTE), relatively more women had abdominal VT than LE DVT/PE, while the proportions with LE DVT/PE and abdominal VT by sex were similar in children. Children with abdominal VT were more likely to have diagnosed inherited thrombophilia, while trauma was more common in children with LE DVT/PE. In conclusion, both children and adults with abdominal VT were younger with a lower BMI than those with LE DVT/PE. Significant differences exist between children and adults in respect to abdominal VT compared to LE DVT/PE.

Predictors of major bleeding in peri-procedural anticoagulation management

BACKGROUND

Appropriate periprocedural management for chronically anticoagulated patients requires assessment of patient-specific thrombosis and bleeding risks. However, predictors of post-procedure bleeding are unknown.

OBJECTIVES

To determine the 3-month cumulative incidence and independent predictors of peri-procedural bleeding in chronically anticoagulated patients requiring temporary warfarin interruption for an invasive procedure.

METHODS

In a protocol driven, cohort study design, all patients referred to the Mayo Clinic Thrombophilia Center for peri-procedural anticoagulation management (1997-2007; n = 2182), were followed forward in time to determine the 3-month cumulative incidence of peri-procedural bleeding (Kaplan-Meier product limit) and potential predictors of bleeding (Cox proportional hazards). Decisions to 'bridge' with low-molecular-weight heparin were based on estimated thromboembolism and bleeding risk.

RESULTS

Indications for chronic anticoagulation included venous thromboembolism (38%), atrial fibrillation (30%) and mechanical heart valves (27%). Of these, 1496 (69%) patients received bridging therapy. The 3-month cumulative incidence rates of major and overall bleeding were 2.1% and 5.1%, respectively. Major bleeding occurred more frequently in patients receiving bridging therapy (3% vs. 1%; P = 0.017). Independent predictors (hazard ratio; 95% confidence interval) of major bleeding included mitral mechanical heart valve (2.2; 1.1-4.3), active cancer (1.8; 1.0-3.1), prior bleeding history (2.6; 1.5-4.5) and re-initiation of heparin therapy within 24 h after the procedure (1.9; 1.1-3.4).

CONCLUSION

Factors predisposing to peri-procedural bleeding are primarily patient-specific. Premature heparin re-initiation is an avoidable provider-specific variable to consider.

Developing public health surveillance for deep vein thrombosis and pulmonary embolism

Deep vein thrombosis (DVT) and pulmonary embolism (PE), collectively known as venous thromboembolism (VTE), are an important and growing public health issue, associated with considerable morbidity and mortality. Presently, there is no national surveillance for DVT and PE. This article provides a summary of an expert workgroup meeting convened January 12, 2010, by the CDC. The purpose of the meeting was to inform CDC on the development of U.S. population-based public health surveillance activities for DVT/PE. Topics discussed included: (1) stakeholders, needs, gaps, and target populations; (2) requirements of surveillance systems; (3) challenges, limitations, and potential barriers to implementation of surveillance activities; and (4) integration of research and education with surveillance activities.

Developing a public health research agenda for women with blood disorders

Bleeding and clotting in women is an issue that directly affects the life of every woman, child, and family worldwide. This article summarizes recent activities undertaken by the Division of Blood Disorders (DBD) at the Centers for Disease Control and Prevention (CDC) to identify risk factors through evidence-based research and surveillance to prevent complications of blood disorders in women. Specific focus is given to our efforts to improve early identification and diagnosis of blood disorders among women, improve our understanding of maternal and infant outcomes, and develop surveillance systems to monitor the prevalence and incidence of these events.

Comparison of characteristics from White- and Black-Americans with venous thromboembolism: a cross-sectional study

When compared with Whites, Black-Americans may have a 40% higher incidence venous thromboembolism (VTE) incidence. However, whether other VTE characteristics and risk factors vary by race is uncertain. To compare demographic and baseline characteristics among White- and Black-Americans with VTE, we used data prospectively collected from consecutive consenting adults enrolled in seven Centers for Disease Control (CDC) Thrombosis and Hemostasis Centers from August 2003 to March 2009. These characteristics were compared among Whites (n = 2002) and Blacks (n = 395) with objectively diagnosed VTE, both overall, and by age and gender. When compared with Whites, Blacks had a significantly higher proportion with pulmonary embolism (PE), including idiopathic PE among Black women, and a significantly higher proportion of Blacks were women. Blacks had a significantly higher mean BMI and a significantly lower proportion with recent surgery, trauma or infection, family history of VTE, and documented thrombophilia (solely from reduced factor V Leiden and prothrombin G20210A prevalence). Conversely, Blacks had a significantly higher proportion with hypertension, diabetes mellitus, chronic renal disease and dialysis, HIV, and sickle cell disease. When compared with White women, Black women had a significantly lower proportion with recent oral contraceptive use or hormone therapy. We conclude that Whites and Blacks differ significantly regarding demographic and baseline characteristics that may be risk factors for VTE. The prevalence of transient VTE risk factors and idiopathic VTE among Blacks appears to be lower and higher, respectively, suggesting that heritability may be important in the etiology of VTE among Black-Americans.

Venous thromboembolism: a public health concern

Venous thromboembolism (VTE), defined as deep vein thrombosis, pulmonary embolism, or both, affects an estimated 300,000-600,000 individuals in the U.S. each year, causing considerable morbidity and mortality. It is a disorder that can occur in all races and ethnicities, all age groups, and both genders. With many of the known risk factors-advanced age, immobility, surgery, obesity-increasing in society, VTE is an important and growing public health problem. Recently, a marked increase has occurred in federal and national efforts to raise awareness and acknowledge the need for VTE prevention. Yet, many basic public health functions-surveillance, research, and awareness-are still needed. Learning and understanding more about the burden and causes of VTE, and raising awareness among the public and healthcare providers through a comprehensive public health approach, has enormous potential to prevent and reduce death and morbidity from deep vein thrombosis and pulmonary embolism throughout the U.S.

The U.S. Thrombosis and Hemostasis Centers pilot sites program

Venous thromboembolism (VTE) is a common disorder associated with significant morbidity and mortality. Despite important advances in understanding the etiology of VTE, delivery of care to patients with thrombosis and thrombophilia is frequently incomplete and highly variable. A comprehensive model of health care has been used successfully to treat and prevent complications for people with hemophilia and other chronic disorders. The effectiveness of an integrated healthcare model for patients with all coagulation disorders has yet to be evaluated. The Division of Hereditary Blood Disorders of the Centers for Disease Control and Prevention (CDC) is collaborating with eight Thrombosis and Hemostasis Centers (pilot sites) to provide health-related services and conduct research directed toward the reduction or prevention of complications of thrombosis and thrombophilia. The initial objectives of the collaboration are to (1) determine the efficacy of integrated multidisciplinary care and prevention services for people with hemostatic disorders, (2) assess unmet needs for service delivery and identify outreach strategies to improve access to care, (3) develop effective messages aimed at disease management and prevention, and (4) foster the development of training programs to enhance provider skills for the delivery of patient care. To address these objectives, the investigators and CDC have developed and implemented a web-based patient registry to follow prospectively service allocation and patient outcomes. Funding for the program began in October 2001. All eight funded centers are affiliated with U.S. medical schools. Principal investigators at the centers are hematologists (five adult, two pediatric) or cardiologists. Faculty in obstetrics-gynecology, surgery, and multiple other specialties are integral to the model of care at the centers. Other critical components at the centers are clinical laboratory services, training programs, research networks, and education and outreach programs. From August 2003 to March 2006, over 2,600 patients were enrolled in the registry, accounting for a total of more than 5,000 visits to the centers. Immediate goals of the data collection at the centers are to characterize patients receiving care at centers and document the state of health services provided. Long-term goals are to evaluate prospectively clinical outcomes for patients receiving multidisciplinary care and prevention services at centers. The network of data collection across centers will facilitate future collaborative clinical and epidemiologic investigations and enhance collective expertise in hemostasis and coagulation disorders.

Asynchronous transfer mode distribution network by use of an optoelectronic VLSI switching chip

We describe a new optoelectronic switching system demonstration that implements part of the distribution fabric for a large asynchronous transfer mode (ATM) switch. The system uses a single optoelectronic VLSI modulator-based switching chip with more than 4000 optical input-outputs. The optical system images the input fibers from a two-dimensional fiber bundle onto this chip. A new optomechanical design allows the system to be mounted in a standard electronic equipment frame. A large section of the switch was operated as a 208-Mbits/s time-multiplexed space switch, which can serve as part of an ATM switch by use of an appropriate out-of-band controller. A larger section with 896 input light beams and 256 output beams was operated at 160 Mbits/s as a slowly reconfigurable space switch.

Five-stage free-space optical switching network with field-effect transistor self-electro-optic-effect-device smart-pixel arrays

The design, construction, and operational testing of a five-stage, fully interconnected 32 × 16 switching fabric by the use of smart-pixel (2, 1, 1) switching nodes are described. The arrays of switching nodes use monolithically integrated GaAs field-effect transistors, multiple-quantum-well p-i-n detectors, and self-electro-optic-device modulators. Each switching node incorporates 25 field-effect transistors and 17 p-i-n diodes to realize two differential optical receivers, the 2 × 1 node switching logic, a single-bit node control memory, and one differential optical transmitter. The five stages of node arrays are interconnected to form a two-dimensional banyan network by the use of Fourier-plane computer-generated holograms. System input and output are made by two-dimensional fiber-bundle matrices, and the system optical hardware design incorporates frequency-stabilized lasers, pupil-division beam combination, and a hybrid micro-macro lens for fiber-bundle imaging. Optomechanical packaging of the system ut lizes modular kinematic component positioning and active thermal control to enable simple rapid assembly. Two preliminary operational experiments are completed. In the first experiment, five stages are operated at 50 Mbits/s with 15 active inputs and outputs. The second experiment attempts to operate two stages of second-generation node arrays at 155 Mbits/s, with eight of the 15 active nodes functioning correctly along the straight switch-routing paths.

Occurrence of Salmonella enteritidis in unpasteurized liquid egg in the United States

In order to gain a greater understanding of the occurrence and distribution of Salmonella enteritidis in the United States, a survey of unpasteurized liquid egg (collected at 20 egg-breaking plants across the United States) was conducted over a 52-week period. Weekly liquid egg samples were submitted for Salmonella culturing at the National Veterinary Services Laboratories. Group D positive salmonellae were serotyped and phage-typed. On a regional basis, the Northern Region of the United States had the highest S. enteritidis recovery, with 20% of the samples submitted from plants in that region culture-positive for this serotype. Salmonella enteritidis positives from the Southeast, Central, and Western regions were 10%, 15%, and 6% of the samples submitted, respectively.