Linda J. Young

Combining Incompatible Spatial Data

Global positioning systems (GPSs) and geographical information systems (GISs) have been widely used to collect and synthesize spatial data from a variety of sources. New advances in satellite imagery and remote sensing now permit scientists to access spatial data at several different resolutions. The Internet facilitates fast and easy data acquisition. In any one study, several different types of data may be collected at differing scales and resolutions, at different spatial locations, and in different dimensions. Many statistical issues are associated with combining such data for modeling and inference. This article gives an overview of these issues and the approaches for integrating such disparate data, drawing on work from geography, ecology, agriculture, geology, and statistics. Emphasis is on state-of-the-art statistical solutions to this complex and important problem.

Clinical Significance of Primary Vesicoureteral Reflux and Urinary Antibiotic Prophylaxis After Acute Pyelonephritis: A Multicenter, Randomized, Controlled Study

OBJECTIVES. To evaluate the role of primary vesicoureteral reflux (VUR) in increasing the frequency and severity of urinary tract infections (UTIs) and renal parenchymal damage among patients with acute pyelonephritis and to determine whether urinary antibiotic prophylaxis reduces the frequency and/or severity of UTIs and/or prevents renal parenchymal damage among patients with mild/moderate VUR. METHODS. Patients 3 months to 18 years of age with acute pyelonephritis, with or without VUR, were assigned randomly to receive urinary antibiotic prophylaxis or not. Patients were monitored every 3 months for 1 year. Dimercaptosuccinic acid renal scans were repeated at 6 months or if there was a recurrence of febrile UTI. Urinalysis and urine culture were performed at each clinic visit. Renal ultrasound scans and voiding cystourethrograms were repeated at the end of 1 year of follow-up monitoring. RESULTS. Of the 236 patients enrolled in the study, 218 completed the 1-year follow-up monitoring. Groups were similar with respect to age, gender, and reflux grade distribution for those with VUR. No statistically significant differences were found among the groups with respect to rate of recurrent UTI, type of recurrence, rate of subsequent pyelonephritis, and development of renal parenchymal scars. CONCLUSIONS. After 1 year of follow-up monitoring, mild/moderate VUR does not increase the incidence of UTI, pyelonephritis, or renal scarring after acute pyelonephritis. Moreover, a role for urinary antibiotic prophylaxis in preventing the recurrence of infection and the development of renal scars is not supported by this study.

RNA-seq: technical variability and sampling.

BackgroundRNA-seq is revolutionizing the way we study transcriptomes. mRNA can be surveyed without prior knowledge of gene transcripts. Alternative splicing of transcript isoforms and the identification of previously unknown exons are being reported. Initial reports of differences in exon usage, and splicing between samples as well as quantitative differences among samples are beginning to surface. Biological variation has been reported to be larger than technical variation. In addition, technical variation has been reported to be in line with expectations due to random sampling. However, strategies for dealing with technical variation will differ depending on the magnitude. The size of technical variance, and the role of sampling are examined in this manuscript.ResultsIn this study three independent Solexa/Illumina experiments containing technical replicates are analyzed. When coverage is low, large disagreements between technical replicates are apparent. Exon detection between technical replicates is highly variable when the coverage is less than 5 reads per nucleotide and estimates of gene expression are more likely to disagree when coverage is low. Although large disagreements in the estimates of expression are observed at all levels of coverage.ConclusionsTechnical variability is too high to ignore. Technical variability results in inconsistent detection of exons at low levels of coverage. Further, the estimate of the relative abundance of a transcript can substantially disagree, even when coverage levels are high. This may be due to the low sampling fraction and if so, it will persist as an issue needing to be addressed in experimental design even as the next wave of technology produces larger numbers of reads. We provide practical recommendations for dealing with the technical variability, without dramatic cost increases.

The Impact of Poststroke Depression on Healthcare Use by Veterans With Acute Stroke

Background and Purpose— Poststroke depression (PSD) is common among stroke survivors, and it is associated with worse functional outcomes and increased poststroke mortality. Limited information is available about its impact on healthcare use. This study assessed the impact of PSD on healthcare use by veterans with acute stroke. Methods— In this retrospective, observational national study, 5825 veterans with acute stroke were identified from Veterans Affairs’ (VA) inpatient databases. To determine the patients’ comprehensive PSD and use status, VA and Medicare fee-for-service inpatient and outpatient as well as VA pharmacy data were used. PSD was established if a patient had an inpatient or outpatient depression diagnosis or if a patient received one of the antidepressants within the VA 12 months postindex stroke. Healthcare use referred to the number of hospital stays, outpatient visits, and cumulative length of inpatient stays under both VA and Medicare fee-for-service programs. Poisson regression was fitted to estimate the impact of PSD on use controlling for sociodemographic, clinical, and disease severity factors. Results— Forty-one percent of the sample had PSD. After adjusting for patient demographic and clinical factors, we found that the patients with stroke with PSD had significantly (P<0.0001) more hospitalizations, outpatient visits, and longer length of stays 12 months poststroke compared with these patients with stroke without PSD. Conclusions— Patients with PSD had greater 12-month poststroke healthcare use even when controlling for other demographic and clinical variables. Early detection and appropriate management of PSD for veterans with acute stroke may help reduce their poststroke healthcare use.

Dispersal of Adult European Corn Borer (Lepidoptera: Crambidae) Within and Proximal to Irrigated and Non-irrigated Corn

Abstract The European corn borer, Ostrinia nubilalis (Hübner), causes economic damage to corn, Zea mays L., throughout the Corn Belt. Because this insect has become the primary target of Bacillus thuringiensis Berliner (Bt) transgenic corn, current efforts addressing the management of O. nubilalis resistance to Bt corn require information on adult European corn borer dispersal and factors affecting its dispersal. In 1998 we conducted mark-release-recapture, release-recapture, and caged-mating studies to directly measure and compare local dispersal patterns of O. nubilalis adults within and proximal to irrigated and non-irrigated cornfields. Releases of marked adults were made corresponding to the first and second flight of O. nubilalis in eastern Nebraska. Adult dispersal was significantly different between irrigated and non-irrigated cornfields. Released adults tended to remain in and near irrigated cornfields, but dispersed out of and away from non-irrigated cornfields. When released at the edge of the cornfield, neither male nor unmated female O. nubilalis displayed an initial tendency to move out of irrigated corn and into the mixed smooth bromegrass (Bromus inermis Leyss) and broadleaf-weed field edge. Mating efficiency in a late-season cornfield was not significantly different than in dense foxtail (Setaria spp.). Generally, we found that adult O. nubilalis dispersal may vary depending on variables such as action-site availability and agronomic practices and their interaction with O. nubilalis life history.

Influence of Corn Phenology on Adult Western Corn Rootworm (Coleoptera: Chrysomelidae) Distribution

Abstract Field studies were designed to more clearly determine how adult western corn rootworm, Diabrotica virgifera virgifera LeConte, population distribution patterns are altered over time by changes and contrasts in corn (Zea mays L.) plant phenology using whole-plant beetle counts as the sampling tool. In 1994, studies were conducted in a model system consisting of a late-planted corn strip placed in the middle of an early-planted cornfield. The system was replicated over three fields. Large-scale variation was modeled using trend-surface regression analysis to describe the relationship between beetle counts and distance from the center of the late-planted strip. In each field, the beetle distribution became greatly skewed toward the late-planted strip when the strip was either in the tassel or silk stage and the surrounding field was ≥ blister stage. In 1995, studies were conducted in and at the interface of two adjacent cornfields that were planted 9 d apart. Count data were analyzed to quantify population density changes at different sampling locations within and among fields over time as crop phenology changed. Rapid positive or negative changes in beetle densities occurred within and among fields as contrasts in corn phenology changed. In both years, the stability of the beetle distribution was strongly influenced by the length of time that a contrast in plant phenology was maintained between adjacent patches of corn. Directional movements of beetles toward pollinating corn and associated semiochemicals could be inferred from both 1994 and 1995 data analyses. Data suggest that contrasts in crop phenology at the interface and among cornfields should be considered when developing beetle sampling programs and interpreting scouting data to improve the accuracy of rootworm management decisions.

Influences of Trees on Abundance of Natural Enemies of Insect Pests: A Review

In this article we review the use of natural enemies in crop pest management and describe research needed to better meet information needs for practical applications. Endemic natural enemies (predators and parasites) offer a potential but understudied approach to controlling insect pests in agricultural systems. With the current high interest in environmental stewardship, such an approach has special appeal as a method to reduce the need for pesticides while maintaining agricultural profitability. Habitat for sustaining populations of natural enemies occurs primarily at field edges where crops and edge vegetation meet. Conservation and enhancement of natural enemies might include manipulation of plant species and plant arrangement, particularly at these edges; and consideration of optimum field sizes, number of edges, and management practices in and near edges. Blending the benefits of agricultural and forestry (windbreak) systems is one promising approach to field edge management that has additional benefits of wind protection and conservation of desirable wildlife species.

Linking health and environmental data in geographical analysis: it's so much more than centroids.

Programs and studies increasingly use existing data from multiple sources (e.g., surveillance systems, health registries, or governmental agencies) for analysis and inference. These data usually have been collected on different geographical or spatial units, with each varying from the ones of interest. Combining such disparate data creates statistical challenges. Floridas efforts to move toward implementing the Centers for Disease Control and Prevention (CDC)s Environmental Public Health Tracking (EPHT) program aptly illustrate these concerns, which are typical of studies designed to measure the association between environmental and health outcomes. In this paper, we develop models of spatial associations between myocardial infarctions (MIs) and ambient ozone levels in Florida during August 2005 and use these models to illustrate the problems that can occur when making inferences from aggregated data, the concept of spatial support, and the importance of correct uncertainty assessment. Existing data on hospital discharges and emergency department visits were obtained from Floridas Agency for Health Care Administration. Environmental data were obtained from Floridas Department of Environmental Protection; sociodemographic data were obtained from the US Census Bureau; and data from CDCs Behavioral Risk Factor Surveillance System were used to provide additional information on other risk factors. We highlight the opportunities and challenges associated with combining disparate spatial data for EPHT analyses. We compare the results from two different approaches to data linkage, focusing on the need to account for spatial scale and the support of spatial data in the analysis. We use geographically weighted regression, not as a visual mapping tool, but as an inferential tool designed to indicate the need for spatial coefficients, a test that cannot be made by using the majority of Bayesian models. Finally, we use geostatistical simulation methods for uncertainty analysis to demonstrate its importance in models with predicted covariates. Our focus is on relatively simple methods and concepts that can be implemented with ESRIs(®) ArcGIS(®) software.

Effects of Sepsis on Neonatal Thrombopoiesis

We serially evaluated the effects of sepsis and/or necrotizing enterocolitis (NEC) on neonatal thrombopoiesis, using a panel of tests that included platelet counts, thrombopoietin concentrations (Tpo), circulating megakaryocyte progenitor concentrations (CMPs), and reticulated platelets (RPs). Variables analyzed included sepsis type, time after onset of sepsis, platelet counts, and gestational (GA) and postconceptional ages (PCA). Twenty neonates were enrolled. Ten had Gram-negative, six had Gram-positive, and four had presumed sepsis. Four neonates had NEC stage II or higher, and six developed thrombocytopenia. Overall, septic neonates had significantly elevated Tpo concentrations and circulating megakaryocyte progenitors. The highest Tpo levels were associated with Gram-negative or presumed sepsis. RP percentages were increased only in neonates with low platelet counts, while RP counts (RP% × platelet count) were elevated in neonates with high platelet counts. Our findings suggest that septic neonates up-regulate Tpo production, leading to increased megakaryocytopoiesis and platelet release, although the degree of upregulation is moderate. The changes in RP% and RP count most likely reflect increased thrombopoiesis with variable degrees of platelet consumption. In addition, our findings suggest that different factors, likely including level of illness and/or specific platelet or bacterial products, can down-regulate the magnitude of the thrombopoietic response.

Geostatistical Analysis of the Small-Scale Distribution of European Corn Borer (Lepidoptera: Crambidae) Larvae and Damage in Whorl Stage Corn

Abstract The small-scale spatial distribution of European corn borer, Ostrinia nubilalis (Hübner), larvae and damage in whorl stage corn, Zea mays L., was characterized using geostatistics. Spatial distribution of O. nubilalis larval feeding damage was studied at Clay Center, North Platte, and Concord, NE, during June–July 1992–1994, and spatial distribution of O. nubilalis larvae and damage was studied at Clay Center in June 1997. Semivariograms were calculated to model the change in spatial correlation with increasing distance between samples. Spatial distribution of larval damage during 1992–1994 was best described using a spherical model. Damage was spatially correlated among plants at distances up to 2.84 m apart. The spatial distribution of larvae in 1997 was best described using an exponential model for three of seven data sets, a spherical model for one of seven data sets and no model fit three of seven data sets. Larvae were spatially correlated among plants at distances up to 3.05 m apart. These data have implications for developing sampling plans for management of O. nubilialis, and for site-specific agriculture.