			Home About us Contact

Increased Precision (increased + precision)

Distribution by Scientific Domains

Medical Sciences	50%

Selected Abstracts

Using form analysis techniques to improve photogrammetric mass-estimation methods

MARINE MAMMAL SCIENCE, Issue 1 2008
Kelly M. Proffitt
Abstract Numerical characterization of animal body forms using elliptical Fourier decomposition may be a useful analytic technique in a variety of marine mammal investigations. Using data collected from the Weddell seal (Leptonychotes weddellii), we describe the method of body form characterization using elliptical Fourier analysis and demonstrated usefulness of the technique in photogrammetric mass-estimation modeling. We compared photogrammetric mass-estimation models developed from (1) standard morphometric measurement covariates, (2) elliptical Fourier coefficient covariates, and (3) a combination of morphometric and Fourier coefficient covariates and found that mass-estimation models employing a combination of morphometric measurements and Fourier coefficients outperformed models containing only one covariate type. Inclusion of Fourier coefficients in photogrammetric mass-estimation models employing standard morphometric measurements reduced the width of the prediction interval by 24.4%. Increased precision of photogrammetric mass-estimation models employing Fourier coefficients as model covariates may expand the range of ecological questions that can be addressed with estimated mass measurements. [source]

Estimation of stage-specific fibrosis progression rates in chronic hepatitis C virus infection: A meta-analysis and meta-regression,

HEPATOLOGY, Issue 2 2008
Hla-Hla Thein
Published estimates of liver fibrosis progression in individuals with chronic hepatitis C virus (HCV) infection are heterogeneous. We aimed to estimate stage-specific fibrosis progression rates and their determinants in these individuals. A systematic review of published prognostic studies was undertaken. Study inclusion criteria were as follows: (1) presence of HCV infection determined by serological assays; (2) available information about age at assessment of liver disease or HCV acquisition; (3) duration of HCV infection; and (4) histological and/or clinical diagnosis of cirrhosis. Annual stage-specific transition probabilities (F0,F1, , , F3,F4) were derived using the Markov maximum likelihood estimation method and a meta-analysis was performed. The impact of potential covariates was evaluated using meta-regression. A total of 111 studies of individuals with chronic HCV infection (n = 33,121) were included. Based on the random effects model, the estimated annual mean (95% confidence interval) stage-specific transition probabilities were: F0,F1 0.117 (0.104,0.130); F1,F2 0.085 (0.075,0.096); F2,F3 0.120 (0.109,0.133); and F3,F4 0.116 (0.104,0.129). The estimated prevalence of cirrhosis at 20 years after the infection was 16% (14%,19%) for all studies, 18% (15%,21%) for cross-sectional/retrospective studies, 7% (4%,14%) for retrospective-prospective studies, 18% (16%,21%) for studies conducted in clinical settings, and 7% (4%,12%) for studies conducted in nonclinical settings. Duration of infection was the most consistent factor significantly associated with progression of fibrosis. Conclusion: Our large systematic review provides increased precision in estimating fibrosis progression in chronic HCV infection and supports nonlinear disease progression. Estimates of progression to cirrhosis from studies conducted in clinical settings were lower than previous estimates. (HEPATOLOGY 2008.) [source]

Modeling Data with Excess Zeros and Measurement Error: Application to Evaluating Relationships between Episodically Consumed Foods and Health Outcomes

BIOMETRICS, Issue 4 2009
Victor Kipnis
Summary Dietary assessment of episodically consumed foods gives rise to nonnegative data that have excess zeros and measurement error. Tooze et al. (2006,,Journal of the American Dietetic Association,106, 1575,1587) describe a general statistical approach (National Cancer Institute method) for modeling such food intakes reported on two or more 24-hour recalls (24HRs) and demonstrate its use to estimate the distribution of the food's usual intake in the general population. In this article, we propose an extension of this method to predict individual usual intake of such foods and to evaluate the relationships of usual intakes with health outcomes. Following the regression calibration approach for measurement error correction, individual usual intake is generally predicted as the conditional mean intake given 24HR-reported intake and other covariates in the health model. One feature of the proposed method is that additional covariates potentially related to usual intake may be used to increase the precision of estimates of usual intake and of diet-health outcome associations. Applying the method to data from the Eating at America's Table Study, we quantify the increased precision obtained from including reported frequency of intake on a food frequency questionnaire (FFQ) as a covariate in the calibration model. We then demonstrate the method in evaluating the linear relationship between log blood mercury levels and fish intake in women by using data from the National Health and Nutrition Examination Survey, and show increased precision when including the FFQ information. Finally, we present simulation results evaluating the performance of the proposed method in this context. [source]

Optimised monitoring of inflammation suppressive therapy (IST) in uveitis

ACTA OPHTHALMOLOGICA, Issue 2009
CP HERBORT
Purpose The array of inflammation suppressive therapies (IST) has increased trumendously in the last two decades including the availability of biological molecules with potent immunomodulatary activities as well as new immunosuppressive agents. In parallel measuring methods for intraocular inflammation have become available allowing much more acurate monitoring of the evolution of inflammation and its response to therapy. In addition to the traditionally used fluorescein angiography (FA), laser flare photometrry (LFP), indocyanine green angiography ICGA) and optical coherence tomography (OCT) are among the new investigational methods that have become available, each of them allowing us to establish inflammatory activity with increased precision and to explore compartments previously poorly accessible. Methods The advantages of each method will be put forward. Illustrative cases will be taken as examples to show the degree of precision obtained by combining the different methods presently at our disposal for the follow-up and monitoring of inflammation suppressive treatment. Results These cases will show that the presently available tools for optimal monitoring of intraocular inflammation allow the clinician to be better aware of the level of inflammatory activity and to better adapt his treatment. Conclusion Not only he availability of potent new therapies but also the possibility to follow more precisely intraocular inflammation with new precise devices has certainly changed the outcome of uveitis cases in recent years. [source]