1,720,999 research outputs found
Non-linearity in the cost-effectiveness frontier
No full textConventional cost-effectiveness decision rules rely on the assumptions that all health care programmes are divisible and exhibit constant returns to scale for a homogeneous population; hence, the path between adjacent programmes on a cost-effectiveness frontier must be linear. In this paper we build a framework to analyse non-linear 'expansion' paths. We model the impact of two key sources of non-linearity: economies of scale or scope in the production of health care; and prioritisation of patients who are most likely to benefit from more expensive and more effective treatments. We conclude that the expansion path might be linear, convex or concave, depending on the situation. The path might also exhibit vertical discontinuity due to fixed costs or horizontal discontinuity due to indivisibility. The efficiency of resource allocation might be improved by empirical estimation of expansion paths. We discuss the advantages and disadvantages of this approach compared with a standard stratified analysi
Health care resource allocation: Is the threshold rule good enough?
No full textWe review the foundations of resource allocation rules based on cost-effectiveness information. Comprehensive approaches, where a total budget is allocated in one go, require estimation of the costs and effects of all available health care programmes, which is unlikely to be practical. A common alternative is to assess individual programmes against a cost-effectiveness threshold. This has been shown to be efficient if the threshold is well calibrated and all programmes can be wholly or partially implemented with constant returns to scale. We discuss the feasibility of these assumptions, and the effects of relaxing them, concluding that programme indivisibility is unlikely to be a serious problem at a national level, but that miscalibration of the threshold and non-constant returns to scale might be. A rule that avoids these difficulties has been proposed previously: a new programme should only be implemented if it can be funded by cancelling another less effective programme. This could never reduce efficiency, unlike the threshold rule, though we show that it might sometimes fail to recommend an efficiency-improving change. We suggest a refinement of this reallocation rule based on explicit estimation of the costs and effects of partial implementation of the programmes under review. Research is required to assess the practicality of this optio
Overview of the clinical effectiveness of positron emission tomography imaging in selected cancers. [Review] [272 refs]
No full textOBJECTIVES: To assess the clinical effectiveness of positron emission tomography (PET) using 2-[18F]-fluoro-2-deoxy-D-glucose (FDG) in breast, colorectal, head and neck, lung, lymphoma, melanoma, oesophageal and thyroid cancers. Management decisions relating to diagnosis, staging/restaging, recurrence, treatment response and radiotherapy (RT) planning were evaluated separately. DATA SOURCES: Major electronic databases were searched up to August 2005 and a survey of UK PET facilities was performed in February 2006. REVIEW METHODS: This assessment augments the systematic search undertaken in a previous review. Studies were limited to those using commercial dedicated PET or PET/computed tomography (CT) devices with FDG, in one of the eight cancers. RESULTS: The new search identified six systematic reviews and 158 primary studies. An economic model for England showed that in non-small cell lung cancer (NSCLC) FDG-PET was cost-effective in CT node-negative patients, but not in CT node-positive patients. A less robust model also showed that FDG-PET was cost-effective in RT planning for NSCLC. A model for Scotland showed that in late-stage Hodgkin's lymphoma (HL), FDG-PET was cost-effective for restaging after induction therapy. For staging/restaging colorectal cancer, FDG-PET changed patient management in a way that can impact on curative therapy. For detection of solitary pulmonary nodule (SPN) there was also impact on patient management, but the resulting effect on patient outcomes was unclear. FDG-PET had an impact on patient management across paediatric lymphoma decisions, but further study of individual management decisions is required. For other cancer management decisions, the evidence on patient management is weak. FDG-PET was accurate in detecting distant metastases across several sites, but sensitivity was variable for detection of lymph-node metastases and poor in early stage disease where sentinel lymph-node biopsy would be used and for small lesions. There were 61 studies of treatment response. These were generally small and covered all cancers except melanoma. They showed that FDG-PET imaging could be correlated with response, in some cases, but the impact on patient management was not documented. There were 17 small studies of RT planning in four cancers; here, FDG-PET led to alteration of RT volumes and doses, but the impact on patient outcomes was not studied. FDG-PET improved diagnostic accuracy compared with alternatives in a number of other cancer management decisions, but more comparative evidence is needed. There were 23 studies of PET/CT in six cancers (excluding breast and melanoma). In these FDG-PET/CT generally improved accuracy by 10-15% over PET, resolving some equivocal images. The survey of PET facilities in the UK showed that PET and PET/CT are being used for a variety of cancer indications. PET facilities are not distributed evenly across the UK and use is inconsistent. Various research studies are underway in most centres, but only a few of these are collaborative studies. There is major variation in throughput and cost per scan (635-1300 pounds). CONCLUSIONS: The strongest evidence for the clinical effectiveness of FDG-PET is in staging NSCLC, restaging HL, staging/restaging colorectal cancer and detection of SPN. Some of these may still require clinical audit to augment the evidence base. Other management decisions require further research to show the impact of FDG-PET on patient management or added value in the diagnostic pathway. It is likely that capital investment will be in the newer PET/CT technology, for which there is less evidence. However, as this technology appears to be slightly more accurate than PET/CT, the PET clinical effectiveness results presented here can be extrapolated to cover PET/CT. PET research could be undertaken on FDG-PET or FDG-PET/CT, using a standard cancer work-up process on typical patients who are seen within the NHS in England. For treatment response and RT planning, the need for larger studies using consistent methods across the UK is highlighted as a priority for all cancers. For all studies, consideration should be given to collaboration across sites nationally and internationally, taking cognisance of the work of the National Cancer Research Institute. [References: 272
The economics of diagnosis
No full textAny population can be divided into two groups, one with the presence of a given disease or condition, and the other without. Diagnosis consists of using tests to sort the population into these groups. Diagnostic tests use a threshold value of a diagnostic variable to distinguish between disease-positive and disease-negative individuals. The analysis of error in diagnostic tests has typically been undertaken using receiver-operator characteristic (ROC) curves. More recently, economic value of information (VOI) methods have characterised the costs and consequences of testing. This paper develops a new method for economic test evaluation, which we call ROTS analysis. The ROTS curve plots the costs and effects of changing test thresholds, in cost-effectiveness space. We illustrate the use of our method with a worked example, and show how it can answer three key questions: (1) Is there any test that is worth doing? (2) What is a test's optimum operating point in terms of sensitivity and specificity? (3) If two tests are available, which is best? We contrast the merits of our method with those of established ROC and VOI analysis. We argue that ROTS analysis more clearly reveals the link between changing test thresholds and the cost-effectiveness of different treatments. Copyright © 2006 John Wiley & Sons, Ltd.
Decision science in cancer research: Evaluation of FDG-PET in the surgical management of NSCLC
No full text
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
- …
