1,721,067 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Carcinoembryonic antigen monitoring to detect recurrence of colorectal cancer: how should we interpret the test results?
Full text linkTo the Editor:It is routine clinical practice, supported by national guidelines in both North America and Europe, to measure blood carcinoembryonic antigen (CEA)1 to detect recurrence of colorectal cancer during follow-up after primary treatment. Blood CEA is usually measured every 3–6 months, and patients with a CEA concentration above an absolute threshold (5 ?g/L according to American Society of Clinical Oncology guidelines) are investigated further by radiological imaging. However, the evidence underpinning both guidelines and routine practice is weak.We recently reported the interim results of the Follow-up After Colorectal Surgery (FACS) trial, a clinical trial comparing different types of posttreatment follow-up in 1200 patients with colorectal cancer (1). This trial confirmed that measuring CEA is an effective way of detecting recurrence at an early stage, thus increasing the number of recurrences that can be treated with curative intent. However, the threshold we applied to define an abnormal CEA concentration (7 ?g/L above the patient's postoperative concentration at trial entry) was more conservative than current guidelines, so we decided to reevaluate our data to assess retrospectively whether we could have done better by applying a different strategy to interpret the CEA result and trigger further investigation.We assessed 3 strategies for interpreting the CEA result based on (a) the result of each test individually; (b) the difference between the individual test result and the patient's own postoperative baseline; and (c) the trend in results over time, calculated by linear regression of the log-transformed CEA values. For each strategy, we assessed the outcome of applying different cutoff thresholds by ROC analysis.In the CEA arms of the FACS trial, blood CEA was measured every 3 months for 2 years after primary treatment was complete, followed by every 6 months for 3 years. All CEA measurements were made by use of a Siemens Centaur XP analyzer using a chemiluminescence immunoassay, at the John Radcliffe Hospital in Oxford, U.K. (which participates in the national external quality assurance scheme). The analysis we report here is based on 6259 individual CEA measurements in 559 patients (90 of whom experienced recurrence). Patients with <2 CEA measurements, repeat tests, and measurements taken after confirmation of cancer recurrence were excluded.The ROC curves for each strategy are shown in Fig. 1. This figure illustrates why CEA should not be used as the only method of monitoring, since no strategy achieved 100% diagnostic sensitivity even when applying cutoff thresholds with unacceptably low levels of diagnostic specificity. The figure also shows that calculating the difference from the patient's baseline concentration is no better than considering the result of each test individually [area under the curve (AUC) 0.73 and 0.74]. However, taking account of the trend in CEA concentrations over time was substantially better than either of the other 2 strategies (AUC 0.90, 95% CI 0.85–0.95). The CEA slope that provided maximal diagnostic sensitivity and specificity was a monthly increase of 1.02 ?g/L
Variations on the Author
Full text link“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
Full text linkWe 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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
What carcinoembryonic antigen level should trigger further investigation during colorectal cancer follow-up? A systematic review and secondary analysis of a randomised controlled trial
Full text linkBackground
Following primary surgical and adjuvant treatment for colorectal cancer, many patients are routinely followed up with blood carcinoembryonic antigen (CEA) testing.
Objective
To determine how the CEA test result should be interpreted to inform the decision to undertake further investigation to detect treatable recurrences.
Design
Two studies were conducted: (1) a Cochrane review of existing studies describing the diagnostic accuracy of blood CEA testing for detecting colorectal recurrence; and (2) a secondary analysis of data from the two arms of the FACS (Follow-up After Colorectal Surgery) trial in which CEA testing was carried out.
Setting and participants
The secondary analysis was based on data from 582 patients recruited into the FACS trial between 2003 and 2009 from 39 NHS hospitals in England with access to high-volume services offering surgical treatment of metastatic recurrence and followed up for 5 years. CEA testing was undertaken in general practice.
Results
In the systematic review we identified 52 studies for meta-analysis, including in aggregate 9717 participants (median study sample size 139, interquartile range 72–247). Pooled sensitivity at the most commonly recommended threshold in national guidelines of 5 µg/l was 71% [95% confidence interval (CI) 64% to 76%] and specificity was 88% (95% CI 84% to 92%). In the secondary analysis of FACS data, the diagnostic accuracy of a single CEA test was less than was suggested by the review [area under the receiver operating characteristic curve (AUC) 0.74, 95% CI 0.68 to 0.80]. At the commonly recommended threshold of 5 µg/l, sensitivity was estimated as 50.0% (95% CI 40.1% to 59.9%) and lead time as about 3 months. About four in 10 patients without a recurrence will have at least one false alarm and six out of 10 tests will be false alarms (some patients will have multiple false alarms, particularly smokers). Making decisions to further investigate based on the trend in serial CEA measurements is better (AUC for positive trend 0.85, 95% CI 0.78 to 0.91), but to maintain approximately 70% sensitivity with 90% specificity it is necessary to increase the frequency of testing in year 1 and to apply a reducing threshold for investigation as measurements accrue.
Limitations
The reference standards were imperfect and the main analysis was subject to work-up bias and had limited statistical precision and no external validation.
Conclusions
The results suggest that (1) CEA testing should not be used alone as a triage test; (2) in year 1, testing frequency should be increased (to monthly for 3 months and then every 2 months); (3) the threshold for investigating a single test result should be raised to 10 µg/l; (4) after the second CEA test, decisions to investigate further should be made on the basis of the trend in CEA levels; (5) the optimal threshold for investigating the CEA trend falls over time; and (6) continuing smokers should not be monitored with CEA testing. Further research is needed to explore the operational feasibility of monitoring the trend in CEA levels and to externally validate the proposed thresholds for further investigation.
Study registration
This study is registered as PROSPERO CRD42015019327 and Current Controlled Trials ISRCTN93652154.
Funding
The main FACS trial and this substudy were funded by the National Institute for Health Research Health Technology Assessment programme
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