Assessment of the multiple components of the variability in the adenoma detection rate in sigmoidoscopy screening, and lessons for training.
ABSTRACT The determinants of the observed variability of adenoma detection rate (ADR) in endoscopy screening have not yet been fully explained.
Between November 1999 and November 2006 13 764 people (7094 men, 6670 women; age range 55-64) underwent screening flexible sigmoidoscopy at five hospital endoscopy units in Turin. To study the determinants of the ADR for distal adenomas, accounting for patient, examiner, and hospital characteristics, we applied a multivariate multilevel regression model.
Average ADRs for all adenomas and for advanced adenomas (size > or = 10 mm, villous component > 20 %, high grade dysplasia) were 13.5 % (range 5.2 %-25.0 %) and 6.4 % (3.1 %-10.7 %) for men, and 8.0 % (2.5 %-14.0 %) and 3.7 % (0.2 % - 7.4 %) for women. In multivariate analysis, increased ADR of advanced adenomas was associated with male gender (odds ratio [OR] 1.78, 95 %CI 1.49 - 2.11), self-report of one first-degree relative with colorectal cancer (CRC) (1.44, 1.11-1.86), or of recent-onset rectal bleeding (1.73, 1.24-2.40). Adjusting for these variables, a significantly lower ADR was found for endoscopists with either a lower rate of incomplete sigmoidoscopy (< 9 %; OR 0.59, 95 %CI 0.41-0.87) or a higher rate (> 12 %; 0.64, 0.45-0.91), or with low activity volume (< 85 sigmoidoscopies/year; 0.66, 0.50-0.86). Residual variability explained by the endoscopy center effect was about 1 % and statistically significant.
Endoscopist performance in flexible sigmoidoscopy CRC screening is highly variable. Low volume of screening activity independently predicts lower ADR, suggesting that operators devoting more time to screening sigmoidoscopy may perform better. Variability among pathologists in adenoma classification might explain part of the residual variability across endoscopy units.
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ABSTRACT: For the design of MIMO (multiple input multiple output) systems, channel models are required that properly describe the behavior of the physical channel. The propagation environment around a mobile station (MS) and a base station (BS) is a multipath environment. Multipath components can be grouped together into so called clusters. We define a cluster as a group of paths with similar directions of departure or arrival in azimuth and elevation and similar time delay of arrival. A 3D deterministic ray-tracing tool is used to calculate the double-directional MIMO channel. The advantage of deterministic ray-tracing in contrast to measurements is that ray-tracing offers the possibility of detailed characterization of all multipaths and investigation of the propagation effects without any constraint concerning the antenna or the measurement equipment. A new automatic procedure to identify clusters in azimuth, elevation and delay at the transmitter and the receiver from ray-tracing data is presented. Based on the ray-tracing simulations, we propose a new iterative procedure to extract multipath clusters. The extracted parameters show clearly that, in macrocellular environments, the number of MS-clusters is much greater than the number of BS-clusters. The presented cluster characteristics help to parameterize MIMO channel models and to make simulation results more realistic.Antennas and Propagation Society International Symposium, 2005 IEEE; 08/2005
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ABSTRACT: Emerging results indicate that screening improves survival of patients with colorectal cancer. Therefore, screening programs are already implemented or are being considered for implementation in Asia, Europe and North America. At present, a great variety of screening methods are available including colono- and sigmoidoscopy, CT- and MR-colonography, capsule endoscopy, DNA and occult blood in feces, and so on. The pros and cons of the various tests, including economic issues, are debated. Although a plethora of evaluated and validated tests even with high specificities and reasonable sensitivities are available, an international consensus on screening procedures is still not established. The rather limited compliance in present screening procedures is a significant drawback. Furthermore, some of the procedures are costly and, therefore, selection methods for these procedures are needed. Current research into improvements of screening for colorectal cancer includes blood-based biological markers, such as proteins, DNA and RNA in combination with various demographically and clinically parameters into a "risk assessment evaluation" (RAE) test. It is assumed that such a test may lead to higher acceptance among the screening populations, and thereby improve the compliances. Furthermore, the involvement of the media, including social media, may add even more individuals to the screening programs. Implementation of validated RAE and progressively improved screening methods may reform the cost/benefit of screening procedures for colorectal cancer. Therefore, results of present research, validating RAE tests, are awaited with interest.Scandinavian journal of gastroenterology 08/2011; 46(11):1283-94. · 2.08 Impact Factor
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ABSTRACT: Although faecal and endoscopic tests appear to be effective in reducing colorectal cancer incidence and mortality, further technological and organizational advances are expected to improve the performance and acceptability of these tests. Several attempts to improve endoscopic technology have been made in order to improve the detection rate of neoplasia, especially in the proximal colon. Based on the latest evidence on the long-term efficacy of screening tests, new strategies including endoscopic and faecal modalities have also been proposed in order to improve participation and the diagnostic yield of programmatic screening. Overall, several factors in terms of both efficacy and costs of screening strategies, including the high cost of biological therapy for advanced colorectal cancer, are likely to affect the cost-effectiveness of CRC screening in the future.Gastroenterology Research and Practice 01/2012; 2012:846985. · 1.62 Impact Factor