oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2019 ( 6 )

2018 ( 22 )

2017 ( 14 )

2016 ( 34 )

Custom range...

Search Results: 1 - 10 of 4222 matches for " Caroline CW Klaver "
All listed articles are free for downloading (OA Articles)
Page 1 /4222
Display every page Item
A Method of Drusen Measurement Based on the Geometry of Fundus Reflectance
R Theodore Smith, Takayuki Nagasaki, Janet R Sparrow, Irene Barbazetto, Caroline CW Klaver, Jackie K Chan
BioMedical Engineering OnLine , 2003, DOI: 10.1186/1475-925x-2-10
Abstract: An interactive semi-automated procedure was developed to level the macular background reflectance for the purpose of morphometric analysis of drusen. 12 color fundus photographs of patients with age-related macular degeneration and drusen were analyzed. After digitizing the photographs, the underlying background pattern in the green channel was leveled by an algorithm based on the elliptically concentric geometry of the reflectance in the normal macula: the gray scale values of all structures within defined elliptical boundaries were raised sequentially until a uniform background was obtained. Segmentation of drusen and area measurements in the central and middle subfields (1000 μm and 3000 μm diameters) were performed by uniform thresholds. Two observers using this interactive semi-automated software measured each image digitally. The mean digital measurements were compared to independent stereo fundus gradings by two expert graders (stereo Grader 1 estimated the drusen percentage in each of the 24 regions as falling into one of four standard broad ranges; stereo Grader 2 estimated drusen percentages in 1% to 5% intervals).The mean digital area measurements had a median standard deviation of 1.9%. The mean digital area measurements agreed with stereo Grader 1 in 22/24 cases. The 95% limits of agreement between the mean digital area measurements and the more precise stereo gradings of Grader 2 were -6.4 % to +6.8 % in the central subfield and -6.0 % to +4.5 % in the middle subfield. The mean absolute differences between the digital and stereo gradings 2 were 2.8 +/- 3.4% in the central subfield and 2.2 +/- 2.7% in the middle subfield.Semi-automated, supervised drusen measurements may be done reproducibly and accurately with adaptations of commercial software. This technique for macular image analysis has potential for use in clinical research.Color fundus photographs have been routinely employed for diagnostic purposes for many years, and fundus photo gradings are c
Understanding Ferguson's δ: time to say good-bye?
Berend Terluin, Dirk L Knol, Caroline B Terwee, Henrica CW de Vet
Health and Quality of Life Outcomes , 2009, DOI: 10.1186/1477-7525-7-38
Abstract: Recently Hankins (re-)introduced Ferguson's coefficient δ as an index of discrimination, to be distinguished from the well-known measurement properties validity and reliability [1,2]. Hankins presented Ferguson's δ as a useful index of the degree to which an instrument discriminates between individuals, being "the ratio of the observed number of between-person differences to the theoretical maximum number possible" [1]. The value of δ varies between 0 (no discrimination at all) and 1 (maximal possible discrimination). The calculation is straightforward and Hankins provided a generalized formula for calculating δ for questionnaires with dichotomous as well as polytomous items.Hankins' paper [1] elicited two critical comments [3,4]. Wyrwich referred to the work of Guyatt [5] who related discrimination tot reliability, theoretically consistent correlations with other measures, and interpretability of small but important differences. Since Hankins failed to present relevant information regarding these issues, Wyrwich concluded that it is impossible to make a judgement on whether Ferguson's δ is a useful index or not [3]. Whereas Hankins stated that discrimination is something else than reliability, Norman expressed the opposite view, i.e. that "reliability is discrimination". Scrutinizing Hankins' examples and adding one of his own, Norman illustrated his main point that Ferguson's δ fails to distinguish between true differences and measurement error [4]. In his response, Hankins remarked that both Norman and Wyrwich made too much of his examples, and seemed to have missed his point, which is that Ferguson's δ is an additional index of an instruments' measurement properties, beside reliability, validity and interpretability, and that Ferguson's δ can only be computed on the assumption that the measurement is valid and reliable [6].In this letter, we will examine how exactly Ferguson's δ 'works' and what δ actually measures. More specifically, we will show that the magni
Measuring Semileptonic Asymmetries in LHCb
Suzanne Klaver,for the LHCb Collaboration
Physics , 2015,
Abstract: The $C\!P$-violating flavour-specific asymmetry in neutral $b$ mesons provides a method for testing the Standard Model. The measurements from the D0 experiment yield values of this asymmetry that disagree with the Standard Model at a level of 3.6 $\sigma$. This contribution discusses the latest LHCb measurements in this sector both from $B^0$ mesons ($a_{\mathrm{sl}}^d$) and $B^0_s$ mesons ($a_{\mathrm{sl}}^s$). Using their 2011 dataset, corresponding to an integrated luminosity of 1.0 $\mathrm{fb}^{-1}$ obtained in 2011, LHCb measured a value of $a_{\mathrm{sl}}^s = (-0.06 \pm 0.50_{\text{stat}} \pm 0.36_{\text{syst}}) \%$. Combining the 2011 and 2012 datasets, with an integrated luminosity of 3 $\mathrm{fb}^{-1}$, LHCb measured $a_{\mathrm{sl}}^d = (-0.02 \pm 0.19_{\text{stat}} \pm 0.30_{\text{syst}}) \%$. These are the most precise measurements of the parameters $a_{\mathrm{sl}}^s$ and $a_{\mathrm{sl}}^d$ to date. Plans for an updated result for $a_{\mathrm{sl}}^s$ using the full 3 $\mathrm{fb}^{-1}$ dataset are discussed. This will include new methods to determine detection asymmetries which are the dominating systematic uncertainty of the 2011 measurement.
Inter-rater agreement and reliability of the COSMIN (COnsensus-based Standards for the selection of health status Measurement Instruments) Checklist
Lidwine B Mokkink, Caroline B Terwee, Elizabeth Gibbons, Paul W Stratford, Jordi Alonso, Donald L Patrick, Dirk L Knol, Lex M Bouter, Henrica CW de Vet
BMC Medical Research Methodology , 2010, DOI: 10.1186/1471-2288-10-82
Abstract: 75 articles evaluating measurement properties were randomly selected from the bibliographic database compiled by the Patient-Reported Outcome Measurement Group, Oxford, UK. Raters were asked to assess the methodological quality of three articles, using the COSMIN checklist. In a one-way design, percentage agreement and intraclass kappa coefficients or quadratic-weighted kappa coefficients were calculated for each item.88 raters participated. Of the 75 selected articles, 26 articles were rated by four to six participants, and 49 by two or three participants. Overall, percentage agreement was appropriate (68% was above 80% agreement), and the kappa coefficients for the COSMIN items were low (61% was below 0.40, 6% was above 0.75). Reasons for low inter-rater agreement were need for subjective judgement, and accustom to different standards, terminology and definitions.Results indicated that raters often choose the same response option, but that it is difficult on item level to distinguish between articles. When using the COSMIN checklist in a systematic review, we recommend getting some training and experience, completing it by two independent raters, and reaching consensus on one final rating. Instructions for using the checklist are improved.Recently, a checklist for the evaluation of the methodological quality of studies on measurement properties of health-related patient-reported outcomes (HR-PROs) - the COSMIN checklist - was developed in an international Delphi study [1]. COSMIN is an acronym for COnsensus-based Standards for the selection of health status Measurement INstruments. This checklist can be used for the appraisal of the methodological quality of studies included in a systematic review of measurement properties of HR-PROs. It can also be used to design and report a study on measurement properties. Also, reviewers and editors could use it to identify shortcomings in studies on measurement properties, and to assess whether the methodological quality of s
The COSMIN checklist for evaluating the methodological quality of studies on measurement properties: A clarification of its content
Lidwine B Mokkink, Caroline B Terwee, Dirk L Knol, Paul W Stratford, Jordi Alonso, Donald L Patrick, Lex M Bouter, Henrica CW de Vet
BMC Medical Research Methodology , 2010, DOI: 10.1186/1471-2288-10-22
Abstract: The issues described in this paper are a reflection of the Delphi process in which 43 panel members participated.The topics discussed are internal consistency (relevance for reflective and formative models, and distinction with unidimensionality), content validity (judging relevance and comprehensiveness), hypotheses testing as an aspect of construct validity (specificity of hypotheses), criterion validity (relevance for PROs), and responsiveness (concept and relation to validity, and (in) appropriate measures).We expect that this paper will contribute to a better understanding of the rationale behind the items, thereby enhancing the acceptance and use of the COSMIN checklist.For the measurement of health-related patient-reported outcomes (HR-PROs) it is important to evaluate the methodological quality of studies in which the measurement properties of these instruments are assessed. When studies on measurement properties have good methodological quality, their conclusions are more trustworthy. A checklist containing standards for design requirements and preferred statistical methods is a useful tool for this purpose. However, there is not much empirical evidence for the content of such a tool. A Delphi study is a useful study design in fields lacking empirical evidence. It is particularly valued for its ability to structure and organize group communication [1].In an international Delphi study we developed the COSMIN (COnsensus-based Standards for the selection of health status Measurement INstruments) checklist for evaluating the methodological quality of studies on measurement properties [2,3]. The checklist contains twelve boxes. Ten boxes can be used to assess whether a study meets the standards for good methodological quality. Nine of these boxes contain standards for the included measurement properties (internal consistency, reliability, measurement error, content validity (including face validity), structural validity, hypotheses testing, and cross-cultural va
Surveillance as an Option for the Treatment of Small Renal Masses
S. Klaver,S. Joniau,H. Van Poppel
Advances in Urology , 2008, DOI: 10.1155/2008/705958
Abstract: Objectives. To review the natural history and biological potential of small renal masses in order to evaluate surveillance as a treatment option. Methods. Literature search of Medline and additional references from non-Medline-indexed publications concerning surveillance of small renal masses. Results. The natural history and biological potential of small renal masses can still not be unambiguously predicted at present. There seems to be no clear correlation between tumour size and presence of benign histology. The majority of small renal masses grow and the majority are cancer, but one cannot safely assume that a lack of growth on serial CT scans is the confirmation of absence of malignancy. Needle core biopsies could be used to help in decision making. They show a high accuracy for histopathological tumour type but are less accurate in evaluating Fuhrman grade. Conclusions. At present, surveillance of small renal masses should only be considered in elderly and/or infirm patients with competing health risks, in those with a limited life expectancy, and in those for whom minimal invasive treatment or surgery is not an option. In all other patients, active surveillance should only be considered in the context of a study protocol. Long-term, prospective studies are needed to provide a more accurate assessment of the natural history and metastastic potential of small renal masses.
Fibroblast biology: Development and differentiation of synovial fibroblasts in arthritis
Jonathan CW Edwards
Arthritis Research & Therapy , 2000, DOI: 10.1186/ar110
Abstract: To follow fibroblast nomenclature, synovial fibroblasts should be defined as nonvascular, nonepithelial cells in synovium that arise locally, by division, during embryogenesis, that are replaced by local division, and that synthesise fibrous matrix proteins. Establishing cell origins and functions is not easy, and it is not absolutely certain that such cells even exist. There is no reliable positive fibroblast marker. However, circumstantial evidence suggests that most common leucocyte antigen (CD45)-negative, nonvascular cells in normal synovium fit the definition.In normal human synovium, fibroblasts show two phenotypes: intimal and subintimal [1] (Fig. 1). Intimal fibroblasts express a specialised range of gene products, including UDPGD, VCAM-1 and complement DAF [1,2,3,4]. The rabbit has two intimal forms, one UDPGD-positive and one VCAM-1-positive. In contrast, both human and rabbit subintimal fibroblasts appear unspecialised. Intimal fibroblasts are known as `fibroblast-like' or `type B' synoviocytes/synovial lining cells [5]. The intimal and subintimal fibroblasts do not remain distinct in tissue culture so the general term `synovial fibroblast' has to be applied (a common source of confusion).Intimal and subintimal fibroblasts may be independent lineages, but the simplest view is of a single lineage that can take on an intimal phenotype in response to local stimuli. Several observations, including that of phenotypic convergence in vitro, support this view. The local stimuli are not known, but the intima does fail to form in immobilised chick embryos [6].In arthritis, defining fibroblast populations is more difficult [1]. It is similar to watching a football game in which the players have randomly swapped shirts. Numerous different functions and origins have been ascribed to cell subpopulations, but the picture currently remains consistent with a single fibroblast population responding to a mixture of normal intimal environmental signals and the signals of an
Can IgG Rheumatoid Factors Explain Everything?
Jo CW Edwards
Arthritis Research & Therapy , 1999, DOI: 10.1186/ar27
Abstract: Molecular modelling indicates that IgG1 RF-based complexes, comprising not more than two or three IgG molecules, should evade complement clearance, cross endothelium, and access tissue macrophages [2]. Recent work indicates that, of the three IgG Fc receptors on macrophages only FcγRIIIa will induce TNFα release in response to complexes of this size [3]. FcγRIIIa is expressed at high level only on macrophages in tissues targeted by rheumatoid arthritis and, in dermis, only at sites where nodules form [4]. The dominant involvement of synovium probably reflects the sensitivity of synovial fibroblasts to TNFα and the resulting tendency to synovial lymphoid metaplasia with local antibody production [5].If IgG RFs are responsible both for their own production and for clinical disease, deletion of IgG RF-committed B cells should produce long term-remission. Initial results from a phase-I therapeutic trial of B cell depletion will be presented.
Bioprospecting the African Renaissance: The new value of muthi in South Africa
Hanspeter CW Reihling
Journal of Ethnobiology and Ethnomedicine , 2008, DOI: 10.1186/1746-4269-4-9
Abstract: A growing demand for herbal medicines in North America and Europe as well as epidemics like Malaria, Tuberculosis and HIV/AIDS in Sub-Sahara African have created an expanding market for indigenous herbal medicines. Traditional healers, plant gatherers, petty traders, research institutions and private corporations have assembled around the issues of standardization and commercialization of local knowledge about plants. In South Africa this coincides with a nation-building project, which promotes the revitalization of local knowledge in the so called "African Renaissance" [1]. The idea of such renaissance is as old as the Pan-Africanist movement and its struggle for a regeneration of the continent after slavery and colonialism [2]. More recently, it was proclaimed by Thabo Mbeki's presidential campaigns as synonymous to a "second liberation struggle" for self-discovery, democratization and economic development. There is reason to assume that the transformation of so called Traditional Medicine (TM) sheds light onto this renaissance by indicating how different regimes of value are brought into conflict. Indeed, the translation of socially and culturally situated local knowledge into global pharmaceuticals creates new forms of agency as well as new power differentials between corporate investors, scientists, plant gatherers, and traditional healers. The present article alludes to the transformation of TM in South Africa by giving an overview of key moments in bioprospecting, the "exploration of biodiversity for commercially valuable genetic and biochemical resources" [3]. It will thereby trace social arenas in which plant based medicines have been assigned biovalue.Catherine Waldby first introduced the concept of biovalue to designate the relationship between the promotion of health, the production of capital and the question of ethics in the context of human tissue and stem cell research [4]. It is generated through the manipulation of biological processes in the labor
Translation and validation of the Dutch language version of the CDC Symptom Inventory for assessment of Chronic Fatigue Syndrome (CFS)
Ruud CW Vermeulen
Population Health Metrics , 2006, DOI: 10.1186/1478-7954-4-12
Abstract: One hundred thirty-nine consecutive patients who visited the CFS Center Amsterdam for the first time were asked to complete the CDC Symptom Inventory in the Dutch Language Version (DLV) together with the usual set of questionnaires. Sixty-one patients had Chronic Fatigue (CF) and 78 patients fulfilled the criteria for CFS. Forty-three healthy accompanying persons completed the CDC Symptom Inventory DLV, the Physical Functioning scale of the Medical Outcome Survey Short Form-36 DLV, and the Fatigue and Concentration scales of the Checklist Individual Strength (CIS-20).The healthy controls group contained fewer women and was overall older than the patient groups. The influence of gender on the CDC Symptom Inventory DLV was significant but the effect of age was not. The Dutch version had a good internal consistency and convergent validity. The results were comparable to the original English version, but the sex-related difference needs further study.The Dutch version of the CDC Symptom Inventory is a reliable tool for the assessment of the secondary criteria for CFS. The results show that it is comparable to the outcome of studies in English speaking countries.Chronic Fatigue Syndrome (CFS) is a disabling state that was defined by a working group in 1994 [1]. The main components of the definition are fatigue that is not related to exercise and not relieved by rest, and eight accompanying symptoms, of which four must be present. The CFS is incapacitating, with a serious reduction in daily activity.Several self-rating scales for the presence and severity of fatigue were developed. Of these, the Multidimensional Fatigue Inventory (MFI-20) [2] and the Checklist Individual Strength (CIS-20) [3] were selected by an international CFS study group [4]. The same group advised the Medical Outcomes Survey Short-Form-36 (SF-36) as the tool for the assessment of functional impairment. For the presence of the accompanying symptoms of CFS, a symptom checklist developed by the Centers
Page 1 /4222
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.