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.
Conference Paper: OFDM modem for ATM based point-multipoint systems[Show abstract] [Hide abstract]
ABSTRACT: In this paper an application of the OFDM modulation to the "last mile" problem and the main algorithms involved are described. Moreover, the architectures of the most important blocks (namely modulator and demodulator) are illustrated and the design methodology is described. The system has been simulated in FPL and FXP arithmetic and a VHDL description has been automatically generated by using COSSAP. Finally the architecture has been synthesized and mapped on FPGAs.Circuits and Systems for Communications, 2002. Proceedings. ICCSC '02. 1st IEEE International Conference on; 02/2002
- [Show abstract] [Hide abstract]
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
- [Show abstract] [Hide abstract]
ABSTRACT: The incidence of colorectal cancer (CRC) has been increasing during the past decades, and the lifetime risk for CRC in industrialised countries is about 5%. CRC is a good candidate for screening, because it is a disease with high prevalence, has recognised precursors, and early treatment is beneficial. This paper outlines the evidence for efficacy from randomised trials for the most commonly used CRC screening tests to reduce CRC incidence and mortality in the average-risk population. Four randomised trials have investigated the effect of guaiac-based fecal occult blood screening on CRC mortality, with a combined CRC mortality risk reduction of 15-17% in an intention-to-screen analysis, and 25% for those people who attended screening. Flexible sigmoidoscopy screening has been evaluated in three randomised trials. The observed reduction in CRC incidence varied between 23 and 80%, and between 27 and 67% for CRC mortality, respectively (intention-to-screen analyses) in the trials with long follow-up time. No randomised trials exist in other CRC screening tools, included colonoscopy screening. FOBT and flexible sigmoidoscopy are the two CRC screening methods which have been tested in randomised trials and shown to reduce CRC mortality. These tests can be recommended for CRC screening.Best practice & research. Clinical anaesthesiology 08/2010; 24(4):417-25. DOI:10.1016/j.bpg.2010.06.005