Varying Data Quality Research Articles

Spatial and temporal epidemiological analysis in the Big Data era

Concurrent with global economic development in the last 50 years, the opportunities for the spread of existing diseases and emergence of new infectious pathogens, have increased substantially. The activities associated with the enormously intensified global connectivity have resulted in large amounts of data being generated, which in turn provides opportunities for generating knowledge that will allow more effective management of animal and human health risks. This so-called Big Data has, more recently, been accompanied by the Internet of Things which highlights the increasing presence of a wide range of sensors, interconnected via the Internet. Analysis of this data needs to exploit its complexity, accommodate variation in data quality and should take advantage of its spatial and temporal dimensions, where available. Apart from the development of hardware technologies and networking/communication infrastructure, it is necessary to develop appropriate data management tools that make this data accessible for analysis. This includes relational databases, geographical information systems and most recently, cloud-based data storage such as Hadoop distributed file systems. While the development in analytical methodologies has not quite caught up with the data deluge, important advances have been made in a number of areas, including spatial and temporal data analysis where the spectrum of analytical methods ranges from visualisation and exploratory analysis, to modelling. While there used to be a primary focus on statistical science in terms of methodological development for data analysis, the newly emerged discipline of data science is a reflection of the challenges presented by the need to integrate diverse data sources and exploit them using novel data- and knowledge-driven modelling methods while simultaneously recognising the value of quantitative as well as qualitative analytical approaches. Machine learning regression methods, which are more robust and can handle large datasets faster than classical regression approaches, are now also used to analyse spatial and spatio-temporal data. Multi-criteria decision analysis methods have gained greater acceptance, due in part, to the need to increasingly combine data from diverse sources including published scientific information and expert opinion in an attempt to fill important knowledge gaps. The opportunities for more effective prevention, detection and control of animal health threats arising from these developments are immense, but not without risks given the different types, and much higher frequency, of biases associated with these data.

When to conduct probabilistic linkage vs. deterministic linkage? A simulation study

IntroductionWhen unique identifiers are unavailable, successful record linkage depends greatly on data quality and types of variables available. While probabilistic linkage theoretically captures more true matches than deterministic linkage by allowing imperfection in identifiers, studies have shown inconclusive results likely due to variations in data quality, implementation of linkage methodology and validation method. The simulation study aimed to understand data characteristics that affect the performance of probabilistic vs. deterministic linkage. MethodsWe created ninety-six scenarios that represent real-life situations using non-unique identifiers. We systematically introduced a range of discriminative power, rate of missing and error, and file size to increase linkage patterns and difficulties. We assessed the performance difference of linkage methods using standard validity measures and computation time. ResultsAcross scenarios, deterministic linkage showed advantage in PPV while probabilistic linkage showed advantage in sensitivity. Probabilistic linkage uniformly outperformed deterministic linkage as the former generated linkages with better trade-off between sensitivity and PPV regardless of data quality. However, with low rate of missing and error in data, deterministic linkage performed not significantly worse. The implementation of deterministic linkage in SAS took less than 1min, and probabilistic linkage took 2min to 2h depending on file size. DiscussionOur simulation study demonstrated that the intrinsic rate of missing and error of linkage variables was key to choosing between linkage methods. In general, probabilistic linkage was a better choice, but for exceptionally good quality data (<5% error), deterministic linkage was a more resource efficient choice.

Quality assessment for Linked Data: A Survey

The development and standardization of semantic web technologies has resulted in an unprecedented volume of data being published on the Web as Linked Data (LD). However, we observe widely varying data quality ranging from extensively curated datasets to crowdsourced and extracted data of relatively low quality. In this article, we present the results of a systematic review of approaches for assessing the quality of LD. We gather existing approaches and analyze them qualitatively. In particular, we unify and formalize commonly used terminologies across papers related to data quality and provide a comprehensive list of 18 quality dimensions and 69 metrics. Additionally, we qualitatively analyze the 30 core approaches and 12 tools using a set of attributes. The aim of this article is to provide researchers and data curators a comprehensive understanding of existing work, thereby encouraging further experimentation and development of new approaches focused towards data quality, specifically for LD.

The Human Story, edited by Graham Lawton. New Scientist, The Collection, Issue 4, 2014. No. of pages: 128. Price: UK£9‐99. ISSN 2054‐6386 (paperback).

It has happened to me more than once. Telling some new acquaintance that I am a palaeontologist, I am expected to be an expert on some extinct backboned vermin that they saw reanimated on television, commonly a dinosaur, but it might be a mammoth or caveman. If the latter, they are soon frustrated by my reply that my knowledge of hominins is no more up to date than Piltdown Man. But no longer; I have enthusiastically devoured The Human Story, and my head is stuffed full of relevant facts, ideas and tit-bits. This book/magazine is ‘…a compilation of classic articles from New Scientist…’ (p. 1) most of which I missed the first time around, but they are now reproduced on higher quality paper than the originals. Although a compilation, changes from one subject to the next within and between chapters are not too jarring. The Human Story follows the well-known style and page size of New Scientist, with the usual zesty intermingling of well-written text, and easily intelligible line drawings (including excellent timelines) and relevant images, all in colour. I emphasise the well-written aspect; subjects as diverse as ancient DNA, viruses, Neogene palaeontology and skeletal morphology are all explained with equal clarity. Each ‘chapter’ is made up of two or more essays. The most relevant to the geologist are ‘The big picture’, ‘Distant origins’, ‘Around the world’ and ‘Extinct cousins’. If I have one criticism of such a readable and well-illustrated volume, it is that there is inconsistency between the diagrams involving geological time between different chapters. Thus, on p. 21, the Paleocene to Recent transition proceeds from left to right; on p. 28, the Recent is at the top of the page; and on p. 32 it has moved to the bottom of the page. All confusing to the casual reader, I am sure. I would also have been more pleased if advertisements were not included. A strength of The Human Story is that it presents science as ideas, not facts. We know what the questions are (but they may change), we have data of variable quality (such as the poor fossil record of hominins) and we think we know what they mean, but different research leaders interpret them in different ways. Multiple interpretations make the text all that more interesting. This is an enthralling way to present ideas that are not trivial or easy to understand, in a format designed to keep the reader riveted. It also demonstrates that the question may be much easier to pose than to answer. The main discussion of the fossil evidence, ‘The origin of our species’ in ‘The big picture’, is brief, but fittingly is the first chapter, and further related aspects pop up in many subsequent sections. The poor fossil record of hominins continues to improve, as it must, and with australopithecines now dating back about 6 million years, the split from the chimpanzee clade is almost discernible from fossils rather than just DNA. The discussion of the bushiness (or not) of the hominin evolutionary phylogenetic tree is all too brief, but alternative topologies are given in later chapters. The Human Story is for any scientist, amateur, student or professional, with an interest in our own evolution. It pulls together our fossil record with the myriad other methods of studying human evolution now available to science. I give this reasonably priced and well-produced volume my full recommendation.

Enhancing 3D post‐stack seismic data acquired in hardrock environment using 2D curvelet transform

ABSTRACTSeismic data acquired in hardrock environment pose a special challenge for processing. Frequent lack of clear coherent events hinders imaging and interpretation. Additional difficulty arises from the presence of significant amount of cultural noise associated with production and processing of ore, which often remains in the processed, stacked data. Motivated by those challenges, we developed an efficient workflow of denoising 3D post‐stack seismic data by using 2D discrete curvelet transform aimed at improving signal‐to‐noise ratio of the data. Our approach is based on the adjustment of the thresholds according to scales and angles in the curvelet domain, making parameterization flexible. We demonstrate effectiveness of our method using 3D post‐stack volumes from the three different mining camps in Canada, which were characterized by variable data quality. Remarkable signal enhancement, confirmed by the improvements in the mean signal‐to‐noise ratio of the dataset, is obtained not only due to random energy attenuation but also by removal of certain features corrupting the data (e.g., acquisition footprint). Comparison with the F‐X/F‐XY deconvolution results shows the superiority of our algorithm in respect to signal enhancement, signal preservation, and amount of the removed noise. Imaged structures, even if initially dominated by random energy, are easier to follow after curvelet denoising and enhanced for interpretation. Therefore, our approach can significantly reduce interpretation uncertainties when dealing with the seismic data acquired in the hardrock environment.

The state of population health surveillance using electronic health records: a narrative review.

Electronic health records (EHRs) are transforming the practice of clinical medicine, but the extent to which they are being harnessed to advance public health goals remains uncertain. Data extracted from integrated EHR networks offer the potential for almost real-time determination of the health status of populations in care, for targeting interventions to vulnerable populations, and for monitoring the impact of such initiatives over time. This is especially true in ambulatory care settings, which are uniquely suited for monitoring population health indicators including risk factors and disease management indicators associated with chronic diseases. As efforts gather steam to integrate health data across delivery systems, large networks of electronic patient information are increasingly emerging. Few of the national population health surveillance systems that rely on EHR data have progressed beyond laying groundwork to launch and maintain EHR-based surveillance, but a limited number of more focused or local efforts have demonstrated innovation in population health surveillance. Common challenges include incompleteness of population coverage, lack of interoperability across data systems, and variable data quality. This review defines progress, opportunities, and challenges in using EHR data for population health surveillance.

Genomic Dissection of the Fcγ Receptor Region in the Context of Monoclonal Antibody Therapy

Development of the anti-CD20 antibody, rituximab, heralded the start of monoclonal antibody (mAb) therapy as an effective means of treating cancer. Despite its undoubted impact, clinical responses remain variable and cures are rarely achieved. Evidence from pre-clinical models and human trials indicates that mAbs primarily act through engaging low-affinity Fc gamma receptor (FcγR)-expressing effector immune cells. The low-affinity FcγR genes, FCGR2A, FCGR2B, FCGR2C, FCGR3A and FCGR3B, are located within a highly homologous 200 kb region at 1q23, which is the result of an ancestral segmental duplication event (Figure 1). The locus also contains numerous single nucleotide polymorphisms (SNPs), many of which can affect receptor affinity and/or function and are associated with differential responses following mAb immunotherapy. Moreover, the region contains extensive copy number variation (CNV) that also can affect the expression and function of these receptors, but its impact on mAb immunotherapy remains unknown.To investigate the full impact of SNPs and CNV in the FcγR locus, we have optimised a number of sensitive and specific assays which are amenable to formalin fixed paraffin embedded (FFPE) material in order to apply them to clinical trial samples in a high-throughput manner. Initially we assessed the accuracy of established TaqMan and novel allele-specific (KASP) genotyping assays for FCGR2A-131H/R (rs1801274), FCGR3A-158F/V (rs396991) and FCGR2B-232I/T (rs1050501) SNPs by analysing 2085 DNA samples derived from peripheral blood lymphocytes (PBL) from a large, multi-centre cohort. Our data showed that although clear discrimination was possible at the FCGR2A-131H/R SNP, we needed additional selective Sanger sequencing to discriminate the FF/FV and IT/TT genotypes for the FCGR3A-158F/V and FCGR2B-232I/T SNPs, respectively. This difficulty in genotype discrimination in the cases of FCGR3A and FCGR2B is likely due to sequence homology with other genes and CNV in the gene regions which complicate assay design and interpretation of certain genotypes. Secondly, we applied a combined KASP genotyping and Sanger sequencing approach to matched PBL DNA and FFPE-extracted DNA from follicular lymphoma (FL) patients [n=14] and showed that while FFPE material was more likely to fail genotyping, successfully genotyped cases were concordant with the matched genomic DNA samples. FFPE samples which failed to amplify PCR products of at least 100 bp using the BIOMED-2 multiplex PCR protocol were more likely to fail genotyping assays.Finally, we assessed the ability of a multiplex ligation-dependent probe amplification (MLPA) assay to concurrently determine SNP genotype and CNV in the low-affinity FCGR locus in a cohort of 155 normal donors and DNA from seven matched PBL-/FFPE-derived FL cases. We employed a paralog ratio test (PRT) assay for FCGR3A and FCGR3B CNV confirmation. In our normal donors, MLPA and PRT results were concordant. 16% of normal donors harboured a deletion [n=15] or duplication [n=10] affecting the FCGR2C locus (A summary of regions of CNV is shown in Figure 1). CNV of FCGR3B was associated with variation at FCGR2C and no CNV was observed in FCGR2A and FCGR2B. CNV affecting FCGR3A was observed in 5% of donors with deletions and duplications in 4 and 5 donors, respectively. In the FFPE-derived DNA samples, we observed elevated variability in data quality that was most noticeable in probes targeting HSPA6, FCGR2C exon 4 and HSPA7. Poor quality data correlated with samples that failed to amplify at least the 100 bp PCR product using the BIOMED-2 multiplex PCR protocol. As such, the preclusion of HSPA6, FCGR2C exon 4 and HSPA7 probes and FFPE samples that failed to amplify any BIOMED-2 PCR product from the analysis permitted the production of high-quality MLPA data. Finally, we designed, and are currently optimising, a targeted re-sequencing platform (Haloplex, Agilent) to interrogate informative regions of the FcγR region, which includes those with unique sequence identify for CNV analysis, and those that include known SNPs.In conclusion, we have evaluated a suite of assays for the genomic analysis of the FcγR locus that are scalable for application in large clinical trials of antibody therapy. This work will ultimately provide a detailed architecture of the region and establish the importance of FcγR genetics in predicting response to antibody therapeutics. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Development of a robust classifier for quality control of reverse-phase protein arrays.

High-throughput reverse-phase protein array (RPPA) technology allows for the parallel measurement of protein expression levels in approximately 1000 samples. However, the many steps required in the complex protocol (sample lysate preparation, slide printing, hybridization, washing and amplified detection) may create substantial variability in data quality. We are not aware of any other quality control algorithm that is tuned to the special characteristics of RPPAs. We have developed a novel classifier for quality control of RPPA experiments using a generalized linear model and logistic function. The outcome of the classifier, ranging from 0 to 1, is defined as the probability that a slide is of good quality. After training, we tested the classifier using two independent validation datasets. We conclude that the classifier can distinguish RPPA slides of good quality from those of poor quality sufficiently well such that normalization schemes, protein expression patterns and advanced biological analyses will not be drastically impacted by erroneous measurements or systematic variations. The classifier, implemented in the "SuperCurve" R package, can be freely downloaded at http://bioinformatics.mdanderson.org/main/OOMPA:Overview or http://r-forge.r-project.org/projects/supercurve/. The data used to develop and validate the classifier are available at http://bioinformatics.mdanderson.org/MOAR.

A systematic review of the effectiveness and cost-effectiveness of peer-based interventions to maintain and improve offender health in prison settings

BackgroundOffender health is deemed a priority issue by the Department of Health. Peer support is an established feature of prison life in England and Wales; however, more needs to be known about the effectiveness of peer-based interventions to maintain and improve health in prison settings.ObjectivesThe study aimed to synthesise the evidence on peer-based interventions in prison settings by carrying out a systematic review and holding an expert symposium. Review questions were (1) what are the effects of peer-based interventions on prisoner health and the determinants of prisoner health?, (2) what are the positive and negative impacts on health services within prison settings of delivering peer-based interventions?, (3) how do the effects of peer-based approaches compare with those of professionally led approaches? and (4) what are the costs and cost-effectiveness of peer-based interventions in prison settings?Data sourcesFor the systematic review, 20 electronic databases including MEDLINE, PsycINFO, the Cumulative Index to Nursing and Allied Health Literature and EMBASE were searched from 1985. Grey literature and relevant websites were also searched. To supplement the review findings 58 delegates, representing a variety of organisations, attended an expert symposium, which provided contextual information.Review methodsTwo reviewers independently selected studies using the following inclusion criteria: population – prisoners resident in prisons and young offender institutions; intervention – peer-based interventions; comparators: review questions 3 and 4 compared peer-led and professionally led approaches; outcomes – prisoner health or determinants of health, organisational/process outcomes or views of prison populations; study design: quantitative, qualitative and mixed-methods evaluations. Two reviewers extracted data and assessed validity using piloted electronic forms and validity assessment criteria based on published checklists. Results from quantitative studies were combined using narrative summary and meta-analysis when appropriate; results from qualitative studies were combined using thematic synthesis.ResultsA total of 15,320 potentially relevant papers were identified of which 57 studies were included in the effectiveness review and one study was included in the cost-effectiveness review; most were of poor methodological quality. A typology of peer-based interventions was developed. Evidence suggested that peer education interventions are effective at reducing risky behaviours and that peer support services provide an acceptable source of help within the prison environment and have a positive effect on recipients; the strongest evidence came from the Listener scheme. Consistent evidence from many predominantly qualitative studies suggested that being a peer deliverer was associated with positive effects across all intervention types. There was limited evidence about recruitment of peer deliverers. Recurring themes were the importance of prison managerial and staff support for schemes to operate successfully, and risk management. There was little evidence on the cost-effectiveness of peer-based interventions. An economic model, developed from the results of the effectiveness review, although based on data of variable quality and a number of assumptions, showed the cost-effectiveness of peer-led over professionally led education in prison for the prevention of human immunodeficiency virus (HIV) infection.LimitationsThe 58 included studies were, on the whole, of poor methodological quality.ConclusionsThere is consistent evidence from a large number of studies that being a peer worker is associated with positive health. Peer support services can also provide an acceptable source of help within the prison environment and can have a positive effect on recipients. This was confirmed by expert evidence. Research into cost-effectiveness is sparse but a limited HIV-specific economic model, although based on a number of assumptions and evidence of variable quality, showed that peer interventions were cost-effective compared with professionally led interventions. Well-designed intervention studies are needed to provide robust evidence including assessing outcomes for the target population, economic analysis of cost-effectiveness and impacts on prison health services. More research is needed to examine issues of reach, utilisation and acceptability from the perspective of recipients and those who choose not to receive peer support.Study registrationThis study was registered as PROSPERO CRD42012002349.FundingThe National Institute for Health Research Health Services and Delivery Research programme.

Data Quality and the Comparative Method: The Case of Primate Group Size

The comparative method is frequently employed to study primate behavior and evolution. The method is used to infer adaptations, and considerable improvements have been made with respect to its implementation. Despite these advances, scant attention has been given to the nature of the data that are used in comparative analyses. This creates a potential problem as data are often compiled from studies conducted by multiple researchers, whose methods may differ, resulting in variation in data quality. In this article, we investigate the quality of data employed in studies of primate group size. Several issues concerning data quality arise when assembling data on group size. For example, data quality may be compromised if group sizes are estimated from censuses, unhabituated groups, or groups with unrecognized individuals. To mitigate these and other data quality issues, we gathered data from the literature on 23 monkeys and apes using well-defined and biologically relevant criteria for inclusion. We compare our results with those of eight published compilations of group size. Most studies did not provide details regarding the criteria for including data. We found that our group size values were uncorrelated or weakly correlated with those from three other studies and differed in a consistent fashion from those of one other study. Because conclusions derived from comparative analyses are only as accurate as the data that they use, future studies should provide details regarding data collection to ensure their reliability.

GraFIX: A semiautomatic approach for parsing low- and high-quality eye-tracking data

Fixation durations (FD) have been used widely as a measurement of information processing and attention. However, issues like data quality can seriously influence the accuracy of the fixation detection methods and, thus, affect the validity of our results (Holmqvist, Nyström, & Mulvey, 2012). This is crucial when studying special populations such as infants, where common issues with testing (e.g., high degree of movement, unreliable eye detection, low spatial precision) result in highly variable data quality and render existing FD detection approaches highly time consuming (hand-coding) or imprecise (automatic detection). To address this problem, we present GraFIX, a novel semiautomatic method consisting of a two-step process in which eye-tracking data is initially parsed by using velocity-based algorithms whose input parameters are adapted by the user and then manipulated using the graphical interface, allowing accurate and rapid adjustments of the algorithms’ outcome. The present algorithms (1) smooth the raw data, (2) interpolate missing data points, and (3) apply a number of criteria to automatically evaluate and remove artifactual fixations. The input parameters (e.g., velocity threshold, interpolation latency) can be easily manually adapted to fit each participant. Furthermore, the present application includes visualization tools that facilitate the manual coding of fixations. We assessed this method by performing an intercoder reliability analysis in two groups of infants presenting low- and high-quality data and compared it with previous methods. Results revealed that our two-step approach with adaptable FD detection criteria gives rise to more reliable and stable measures in low- and high-quality data.

Validity of the Surveillance Quality Indicators - Timeliness and Completeness - in Surveillance Systems with Variable Data Quality

Timeliness and Completeness of the routine surveillance reports are surveillance quality indicators which are widely used for monitoring the surveillance quality. However our study shows that in maturing surveillance systems with variable data quality these quality indicators do not provide valid indication of quality. Maturing surveillance systems that have variable data quality should have more comprehensive indicators - including all surveillance system components and core and support surveillance functions - for monitoring surveillance quality.

Abstract 18324: Complication Rates of Atrial Fibrillation Ablations: A Comparison of Outcomes From a National Administrative Database to Contemporary Randomized Control Trials

Introduction: The availability, national scope and perceived unbiased nature of administrative data make it the preferred choice for evaluating quality and outcomes. We calculated Atrial Fibrillation ablation complication rates from national administrative data and compared them with data from randomized control trials (RCT). Methods: Using the Nationwide Inpatient Sample (NIS) we identified patients treated with AF ablations. We investigated complications described with AF ablation and defined them by validated Clinical Modification (ICD-9-CM) diagnosis codes. We compared them with the complication rates reported from AF ablation from widely quoted RCTs. (AF ablation vs. Antiarrhythmics) Results: We analyzed complication rates from 47042 AF ablations performed from the years 2000 to 2008 from the NIS. We also analyzed pooled complication rates from large RCTs. Cardiac tamponade and/or effusion and vascular access complication appear to be the most frequent complications. The NIS data had a higher rate of cardiac tamponade/effusion (21.5 vs. 12.5), vascular access complications (21.2 vs. 19.7) and deaths (4.0 vs. 3.0) when compared to RCTs. Interestingly, RCTs reported a higher rate of stroke/TIA (13.2 vs. 7) when compared to the national administrative data. Conclusion: Despite substantial improvement, “real-world” complication rates from administrative data remain higher than those reported in RCTs. The discrepancy may be attributable to differences in operator skills, selection bias and variation in data quality.

Recovery Trends in Marine Mammal Populations

Marine mammals have greatly benefitted from a shift from resource exploitation towards conservation. Often lauded as symbols of conservation success, some marine mammal populations have shown remarkable recoveries after severe depletions. Others have remained at low abundance levels, continued to decline, or become extinct or extirpated. Here we provide a quantitative assessment of (1) publicly available population-level abundance data for marine mammals worldwide, (2) abundance trends and recovery status, and (3) historic population decline and recent recovery. We compiled 182 population abundance time series for 47 species and identified major data gaps. In order to compare across the largest possible set of time series with varying data quality, quantity and frequency, we considered an increase in population abundance as evidence of recovery. Using robust log-linear regression over three generations, we were able to classify abundance trends for 92 spatially non-overlapping populations as Significantly Increasing (42%), Significantly Decreasing (10%), Non-Significant Change (28%) and Unknown (20%). Our results were comparable to IUCN classifications for equivalent species. Among different groupings, pinnipeds and other marine mammals (sirenians, polar bears and otters) showed the highest proportion of recovering populations, likely benefiting from relatively fast life histories and nearshore habitats that provided visibility and protective management measures. Recovery was less frequent among cetaceans, but more common in coastal than offshore populations. For marine mammals with available historical abundance estimates (n = 47), larger historical population declines were associated with low or variable recent recoveries so far. Overall, our results show that many formerly depleted marine mammal populations are recovering. However, data-deficient populations and those with decreasing and non-significant trends require attention. In particular, increased study of populations with major data gaps, including offshore small cetaceans, cryptic species, and marine mammals in low latitudes and developing nations, is needed to better understand the status of marine mammal populations worldwide.

Quality assurance of near-surface wind velocity measurements in Mexico

A comprehensive quality assurance (QA) procedure applied to the wind velocity records of the automated surface observation network of the Mexican National Weather Service has been conducted for the first time. The analysis covers a total of 139 stations with site-specific measurement periods ranging from 1 to 12 years. The QA process integrates 11 QA checks grouped into 4 categories (plausible value check, internal consistency, temporal consistency, and systematic errors). The fraction of the records flagged by the quality-control (QC) filters is substantial, with nearly 26% of all wind speed records and 5% of all wind direction records showing anomalies. Most error candidates were found to fall in the systematic error and temporal consistency categories, with 10 and 12% of the cases occurring in these categories, respectively. A significant variation of data quality over time was observed, showing both a build-up of errors over time in early stations as well as the results of a learning curve in stations installed more recently. In the case of the earliest stations, installed between 1999 and 2001, a peak in anomalies is observed about 4 years after installation with a subsequent reduction and a second peak after about 10 years. While stations installed between 2002 and 2004 show similar patterns, with error frequency peaking after about 5 years, stations installed more recently, between 2002 and 2006 show a greatly improved behaviour. The results communicated in this paper should provide useful input information for validation of mesoscale wind maps and improved data assimilation procedures.

Core-Analysis Elephant in the Formation-Evaluation Room

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 158087, ’The Core-Analysis Elephant in the Formation-Evaluation Room,’ by Colin McPhee, SPE, Senergy Limited, prepared for the 2012 SPE Annual Technical Conference and Exhibition, San Antonio, Texas, 8-10 October. The paper has not been peer reviewed. The variable data quality of core analysis, the sensitivity of results to different test methods, poor reporting standards, and the reluctance of some vendors to share experience and expertise have contributed to basic mistakes and poor data quality. In many cases, an inconsistent or inappropriate approach to the design, management, and interpretation of the core-analysis program has been adopted and exacerbated by the conflicting requests from the end users. In combination, approximately 70% of legacy special-core-analysis-laboratory (SCAL) data are not fit for purpose. A core-analysis-management road map was designed to increase the value from core-analysis investments by enabling a more-proactive, more-coherent, and more-consistent approach to program design and data acquisition. Introduction In hydrocarbons-in-place and core analysis, the volume of stock-tank oil initially in place in a reservoir can be calculated. The gross rock volume and gross factor in the net-/gross-pay ratio are the primary responsibilities of geophysicists and geologists. The reservoir engineer is responsible for oil-formation-volume factor from pressure/volume/temperature experiments. The petrophysicist is responsible for net reservoir thickness, porosity ø, and water saturation. Data input relies principally on logs, but log interpretation must be calibrated or verified by measurements on cores. For example, net reservoir thickness normally is defined by a permeability cutoff, and high-resolution permeability data are available only from core analysis. Porosity interpretation (e.g., from density logs) should be verified by, or calibrated to, stressed-core porosity data. Resistivity logs require Archie’s cementation and saturation exponents m and n, respectively, to determine water saturation quantitatively in clean formations. These exponents are measured on cores. Water saturation can be determined directly by extracting water from cores with Dean-Stark methods, or indirectly from core-derived capillary pressure measurements. Importance of Core Data and Data Issues. Core analysis is the only direct and quantitative measurement of the intact-reservoir properties, and it should provide the foundation for formation evaluation. However, the author found an unfortunate negativity about the value of core data. In a multiple-laboratory comparative SCAL study, it was found that some core-service contractors provided very-poor-quality data on some of the tests, and it was concluded that some of the laboratories do not have in-house quality-control protocols and report data just as acquired. Other studies have found inexplicable relative- permeability-data discrepancies between commercial laboratories testing exactly the same core material and fluids. Too often, core-analysis programs are ill considered, badly designed, and poorly supervised and the results are only crudely integrated with other well and reservoir data. The results, in terms of data acquired, often are unrepresentative or even contradictory. A conservative estimate from review and audit of more than 30,000 SCAL measurements of different vintages indicates that approximately 70% of the data are unfit for purpose because of their unreliability, inapplicability, or inappropriateness.

Focus

Focus

Flow-R, a model for susceptibility mapping of debris flows and other gravitational hazards at a regional scale

Abstract. The development of susceptibility maps for debris flows is of primary importance due to population pressure in hazardous zones. However, hazard assessment by process-based modelling at a regional scale is difficult due to the complex nature of the phenomenon, the variability of local controlling factors, and the uncertainty in modelling parameters. A regional assessment must consider a simplified approach that is not highly parameter dependant and that can provide zonation with minimum data requirements. A distributed empirical model has thus been developed for regional susceptibility assessments using essentially a digital elevation model (DEM). The model is called Flow-R for Flow path assessment of gravitational hazards at a Regional scale (available free of charge under http://www.flow-r.org) and has been successfully applied to different case studies in various countries with variable data quality. It provides a substantial basis for a preliminary susceptibility assessment at a regional scale. The model was also found relevant to assess other natural hazards such as rockfall, snow avalanches and floods. The model allows for automatic source area delineation, given user criteria, and for the assessment of the propagation extent based on various spreading algorithms and simple frictional laws. We developed a new spreading algorithm, an improved version of Holmgren's direction algorithm, that is less sensitive to small variations of the DEM and that is avoiding over-channelization, and so produces more realistic extents. The choices of the datasets and the algorithms are open to the user, which makes it compliant for various applications and dataset availability. Amongst the possible datasets, the DEM is the only one that is really needed for both the source area delineation and the propagation assessment; its quality is of major importance for the results accuracy. We consider a 10 m DEM resolution as a good compromise between processing time and quality of results. However, valuable results have still been obtained on the basis of lower quality DEMs with 25 m resolution.

Risk-based indicators of Canadians’ exposures to environmental carcinogens

BackgroundTools for estimating population exposures to environmental carcinogens are required to support evidence-based policies to reduce chronic exposures and associated cancers. Our objective was to develop indicators of population exposure to selected environmental carcinogens that can be easily updated over time, and allow comparisons and prioritization between different carcinogens and exposure pathways.MethodsWe employed a risk assessment-based approach to produce screening-level estimates of lifetime excess cancer risk for selected substances listed as known carcinogens by the International Agency for Research on Cancer. Estimates of lifetime average daily intake were calculated using population characteristics combined with concentrations (circa 2006) in outdoor air, indoor air, dust, drinking water, and food and beverages from existing monitoring databases or comprehensive literature reviews. Intake estimates were then multiplied by cancer potency factors from Health Canada, the United States Environmental Protection Agency, and the California Office of Environmental Health Hazard Assessment to estimate lifetime excess cancer risks associated with each substance and exposure pathway. Lifetime excess cancer risks in excess of 1 per million people are identified as potential priorities for further attention.ResultsBased on data representing average conditions circa 2006, a total of 18 carcinogen-exposure pathways had potential lifetime excess cancer risks greater than 1 per million, based on varying data quality. Carcinogens with moderate to high data quality and lifetime excess cancer risk greater than 1 per million included benzene, 1,3-butadiene and radon in outdoor air; benzene and radon in indoor air; and arsenic and hexavalent chromium in drinking water. Important data gaps were identified for asbestos, hexavalent chromium and diesel exhaust in outdoor and indoor air, while little data were available to assess risk for substances in dust, food and beverages.ConclusionsThe ability to track changes in potential population exposures to environmental carcinogens over time, as well as to compare between different substances and exposure pathways, is necessary to support comprehensive, evidence-based prevention policy. We used estimates of lifetime excess cancer risk as indicators that, although based on a number of simplifying assumptions, help to identify important data gaps and prioritize more detailed data collection and exposure assessment needs.

Appropriateness of ICD-coded Diagnostic Inpatient Hospital Discharge Data for Medical Practice Assessment

We performed a systematic review to investigate the quality of diagnostic hospital discharge data (DHDD) in order to gain insight in the usefulness of these data for medical practice assessment. We investigated the methods used to evaluate data quality, factors that determine data quality and its consequences for medical practice assessment. We selected studies in which both completeness (or sensitivity: SENS) and correctness (or positive predictive value: PPV) were measured. We used the random-effects model to calculate mean SENS and PPV and to explore the effect of a number of covariates. The 101 included studies were very heterogeneous. We distinguished six typical study designs. We found a mean SENS of 0.67 (95%CI: 0.62-0.73) and PPV of 0.76 (95%CI: 0.73-0.79); SENS was significantly lower for comorbidity and complication studies than for some single disease studies. PPV was significantly higher for Scandinavian countries than for other countries. Recoding compared to re-abstracting of the medical record as a gold standard gave a significantly lower PPV. Diagnostic data were considered appropriate by the authors of the studies for quality of care purposes when both SENS and PPV were at least 0.85. Only 13% of the studies fulfilled this criterion. Variability in quality of care between settings can easily be overshadowed by variability in data quality. However, the use of DHDD by physicians to evaluate their own medical practice may be useful. But only if physicians are willing to critically interpret the meaning of the information for their medical practice assessment.