1,721,188 research outputs found
Optimalisatie van de formules ter inschatting van de glomerulaire filtratiesnelheid bij kinderen, adolescenten en volwassenen
No full textThe glomerular filtration rate (GFR) is widely considered as the best overall index of kidney function in health and disease. Direct measurements of GFR are technically complicated and impractical to perform in routine clinical settings. That is why more simple methods to estimate the GFR are so successful. The calculation of the estimated (e)GFR using mathematical formulas has been encouraged as a simple, rapid and reliable way of assessing kidney function. In those formulas, serum creatinine (Scr) is most commonly used as a marker for renal function. A typical problem related to the use of creatinine-based eGFR-formulas is the existing diversity of methods to determine Scr. It has been shown that small analytical changes in Scr can create major shifts in the distributions of eGFR-results, which then cause differences in the Chronic Kidney Disease (CKD) classification of patients. So it is clear that control of laboratory analysis of Scr and worldwide standardized Scr measurements are necessary. Manufacturers already made efforts to standardize their Scr measurements to have calibration traceable to the isotope dilution mass spectrometry (IDMS) gold standard method. However calibration traceability does not address (analytical) non-specificity which remains of concern. Lately there have been recommendations to abandon the Jaffe Scr assay in favor of the enzymatic Scr assay since the enzymatic assays have been reported to have generally fewer interferences than the Jaffe methods. However the higher cost of the enzymatic assay is the main reason why some clinical labs still use Jaffe or compensated (compensation made for the mean creatinine-interference) Jaffe assays. Because of the evolution in laboratory testing of Scr to IDMS-standardized techniques, new eGFR-formulas have been developed for adults and children during the last decade but no attempts have been undertaken to develop new formulas for adolescents. Pediatric eGFR-formulas are often used in the adolescent population although these equations were not developed to be used in these patients and are not accurate for the adolescent population. Besides the use of eGFR-formulas, clinicians also often rely on 24-hour creatinine clearance (24h-CrCl) to estimate the kidney function. An advantage over the use of eGFR-formulas is that CrCl can be performed in people of all ages and in patients for whom Scr-based eGFR-formulas are not applicable (eg. pregnant women). However CrCl-determination has also its own specific problems such as the lack of accuracy of the 24h-urine collection and the huge diversity in serum and urine creatinine measurement methods which may lead to different CrCl-results.
In the first part of this PhD-project (Chapter 2) we focused on the problems that may arise when working with Scr assays. To investigate the effect of Scr assays on 24h-CrCl we have set up a study to compare the CrCl calculated from three different type of assays (Jaffe (J), compensated Jaffe (CJ) and enzymatic (E) assay). We showed that CrCl determination is extremely assay-dependent. To evaluate the reliability of 24h-CrCl for estimating the kidney function, we compared the CrCl with eGFR-values calculated with the CKD-EPI eGFR-formula. The deviation of the body surface area indexed CrCl from the CKD-EPI eGFR illustrates that the use of CrCl in clinical practice remains questionable. Two compensating errors in the CrCl-J calculation result in a closer agreement with CKD-EPI eGFR, than between CrCl-CJ or CrCl-E and CKD-EPI eGFR. We therefore recommend clinical labs that work with compensated Jaffe assays not to compensate for the protein effect when a CrCl is requested. In a second study we investigated the accuracy and precision of commonly used Scr assays (J, CJ and E) in Flanders. Our interest was to study how results can vary among laboratories using different type of Scr assays and instruments. We conclude that although most assays claim to be traceable to IDMS, large inter-assay differences still exist. The inaccuracy in the lower concentration range is of particular concern and may lead to clinical misinterpretation when the creatinine-based eGFR of the patient is used for CKD staging.
The second objective of the PhD-project (Chapter 3) was to develop and validate an equation based on IDMS-standardized Scr for estimating the GFR in adolescents. The new formula is based on the concept of population-normalized Scr. We first introduced this concept by reshaping existing eGFR-formulas for adults. Then we showed that the same concept could be used to develop a simple height-independent eGFR-formula for children. Next we extended the idea of normalized Scr to develop and validate two new eGFR-equations for adolescents and young adults. We also illustrated that the newly developed formulas have their limitations and are not applicable in patients with abnormally low Scr, such as Duchenne muscular dystrophy patients. Since separate equations for children, adolescents, adults and elderly lack continuity with aging, we also proposed a GFR estimating equation (by extending the equations for children and adolescents based on population-normalized Scr) valid for the full age spectrum.
In the third part of the PhD-project (Chapter 4) we criticize the current CKD classification system which has been developed for adults, but is also considered to be applicable for children and adolescents. We presented an alternative CKD classification system based on normalized Scr. The alternative approach has the advantage of reducing the proportion of elderly that are (falsely) classified with CKD and increases sensitivity in classifying CKD in children and young adults. We also showed that abnormal GFR for children, adolescents and young adults starts below 75mL/min/1.73m², suggesting that this would be a good alternative for the CKD cut-off of 60 mL/min/1.73m².status: Publishe
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Laparoscopic right posterior sectionectomy: single-center experience and technical aspects
No full textPurposeLaparoscopic right posterior sectionectomy (LRPS) is a technically demanding procedure. The aim of this article is to share our experience with LRPS and to highlight technical aspects of this procedure.MethodsThis is a single-center retrospective analysis of all patients who underwent LRPS between September 2011 and October 2017. Data were retrieved from a prospectively maintained database. Video-in-picture (VIP) technology is used to facilitate and to highlight the technical aspects of this procedure.ResultsIn total, 18 patients underwent LRPS. Indication for surgery was mainly liver metastases (n=11) and hepatocellular carcinoma (n=6). The Glissonean approach for inflow control was used in 13 patients. Median operative time was 162 (140-190) minutes. Median blood loss was 325mL (IQR: 150-450). One conversion (5.5%) was required. There were two minor complications and one major complication. Median hospital stay was 6days (range 5-8days). All patients had an R0 resection. There was no 90-day mortality.ConclusionThe results of our experience in LRPS add weight to the feasibility and safety of this approach
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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