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Optimal Threshold (optimal + threshold)
Selected AbstractsBrain Natriuretic Peptide and Diastolic Dysfunction in the Elderly: Influence of GenderCONGESTIVE HEART FAILURE, Issue 2 2005Chanwit Roongsritong MD Diastolic heart failure is common in the elderly, particularly women. Previous studies on the value of brain natriuretic peptide in diastolic dysfunction have been largely limited to male subjects. The authors found that female gender, in addition to diastolic function, is an independent predictor of brain natriuretic peptide levels in the elderly without systolic ventricular dysfunction. The authors' data indicate that an optimal threshold of brain natriuretic peptide for detecting diastolic dysfunction should be qender-specific. [source] A CRITICAL LOOK AT PAP ADEQUECY: ARE OUR CRITERIA SATISFACTORY?CYTOPATHOLOGY, Issue 2006D.R. Bolick Liquid based Pap (LBP) specimen adequacy is a highly documented, yet poorly understood cornerstone of our GYN cytology practice. Each day, as cytology professionals, we make adequacy assessments and seldom wonder how the criteria we use were established. Are the criteria appropriate? Are they safe? What is the scientific data that support them? Were they clinically and statistically tested or refined to achieve optimal patient care? In this presentation, we will take a fresh look at what we know about Pap specimen adequacy and challenge some of the core assumptions of our daily practice. LBP tests have a consistent, well-defined surface area for screening, facilitating the quantitative estimates of slide cellularity. This provides an unprecedented opportunity to establish reproducible adequacy standards that can be subjected to scientific scrutiny and rigorous statistical analysis. Capitalizing on this opportunity, the TBS2001 took the landmark step to define specimen adequacy quantitatively, and set the threshold for a satisfactory LBP at greater than 5,000 well visualized squamous epithelial cells. To date, few published studies have attempted to evaluate the validity or receiver operator characteristics for this threshold, define an optimal threshold for clinical utility or assess risks of detection failure in ,satisfactory' but relatively hypocellular Pap specimens. Five years of cumulative adequacy and cellularity data of prospectively collected Pap samples from the author's laboratory will be presented, which will serve as a foundation for a discussion on ,Pap failure'. A relationship between cellularity and detection of HSIL will be presented. Risk levels for Pap failure will be presented for Pap samples of different cellularities. The effect of different cellularity criterion on unsatisfactory Pap rates and Pap failure rates will be demonstrated. Results from this data set raise serious questions as to the safety of current TBS2001 adequacy guidelines and suggest that the risk of Pap failure in specimens with 5,000 to 20 000 squamous cells on the slide is significantly higher than those assumed by the current criteria. TBS2001 designated all LBP to have the same adequacy criterion. Up to this point, it has been assumed that ThinPrep, SurePath, or any other LBP would be sufficiently similar that they should have the same adequacy criteria. Data for squamous cellularity and other performance characteristics of ThinPrep and SurePath from the author's laboratory will be compared. Intriguing data involving the recently approved MonoPrep Pap Test will be reviewed. MonoPrep clinical trial data show the unexpected finding of a strong correlation between abundance of endocervical component and the detection of high-grade lesions, provoking an inquiry of a potential new role for a quantitative assessment of the transition zone component. The current science of LBP adequacy criteria is underdeveloped and does not appear to be founded on statistically valid methods. This condition calls us forward as a body of practitioners and scientists to rigorously explore, clarify and define the fundamental nature of cytology adequacy. As we forge this emerging science, we will improve diagnostic performance, guide the development of future technologies, and better serve the patients who give us their trust. Reference:, Birdsong GG: Pap smear adequacy: Is our understanding satisfactory? Diagn Cytopathol. 2001 Feb; 24(2): 79,81. [source] Adaptive directional-aware location update strategyINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 2 2004Tracy Tung Abstract In this paper, a new tracking strategy, the directivity-aware location updating scheme was developed to better utilize the distinct characteristics of individual users on travelling directions. In this new adaptive scheme, an optimal distance-based update threshold is selected according to the call-to-mobility ratio and a transitional directivity index, introduced to give indications of the mobile's travelling patterns. It is found that as far as mobility characteristics are concerned, the actual transitional direction of roaming mobiles plays a significant role in selecting the optimal threshold in addition to the usual perception about mobility rate. Its advantage becomes even more visible when an optimal threshold is not theoretically obtainable due to certain restrictions imposed by the network during times of high system loadings. Simulation results show that the additional information made available about roaming mobile's transitional directivity is critical to ensure that the best available sub-optimal threshold is realizable. Other advances in this paper include the simplification of existing Markovian movement model. With the improved model presentation, the number of states necessary to simulate such memoryless movements is reduced. Consequently, the computational complexity involved is also lessened. Copyright © 2004 John Wiley & Sons, Ltd. [source] In silico prediction and screening of ,-secretase inhibitors by molecular descriptors and machine learning methodsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 6 2010Xue-Gang Yang Abstract ,-Secretase inhibitors have been explored for the prevention and treatment of Alzheimer's disease (AD). Methods for prediction and screening of ,-secretase inhibitors are highly desired for facilitating the design of novel therapeutic agents against AD, especially when incomplete knowledge about the mechanism and three-dimensional structure of ,-secretase. We explored two machine learning methods, support vector machine (SVM) and random forest (RF), to develop models for predicting ,-secretase inhibitors of diverse structures. Quantitative analysis of the receiver operating characteristic (ROC) curve was performed to further examine and optimize the models. Especially, the Youden index (YI) was initially introduced into the ROC curve of RF so as to obtain an optimal threshold of probability for prediction. The developed models were validated by an external testing set with the prediction accuracies of SVM and RF 96.48 and 98.83% for ,-secretase inhibitors and 98.18 and 99.27% for noninhibitors, respectively. The different feature selection methods were used to extract the physicochemical features most relevant to ,-secretase inhibition. To the best of our knowledge, the RF model developed in this work is the first model with a broad applicability domain, based on which the virtual screening of ,-secretase inhibitors against the ZINC database was performed, resulting in 368 potential hit candidates. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010 [source] An objective, rapid and reproducible method for scoring AFLP peak-height data that minimizes genotyping errorMOLECULAR ECOLOGY RESOURCES, Issue 4 2008R. WHITLOCK Abstract Amplified fragment length polymorphism (AFLP) fingerprint data are now commonly collected using DNA sequencers. AFLP genotypes are still often scored by eye from such data , a time-consuming, error-prone and subjective process. We present a semi-automated method of genotyping sequencer-collected AFLPs at predefined fragment locations (loci) within the fingerprint. Our method uses thresholds of AFLP-polymerase chain reaction-product fluorescence intensity (peak height) in order to: (i) exclude AFLP loci that are likely to contribute high rates of error to data sets, and (ii) determine the AFLP phenotype (fragment presence or absence) at the retained loci. Error rate analysis is an integral part of this process and is used to determine optimal thresholds that minimize genotyping error, while maximizing the numbers of retained loci. We show that application of this method to a large AFLP data set allows genotype calls that are rapid, objective and repeatable, facilitating the extraction of reliable genotype data for molecular ecological studies. [source] | ||||||||||