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True Difference (true + difference)

Distribution by Scientific Domains

Medical Sciences	40%
Life Sciences	30%

Selected Abstracts

The efficacy of dantrolene sodium in controlling exertional rhabdomyolysis in the Thoroughbred racehorse

EQUINE VETERINARY JOURNAL, Issue 7 2003
J. G. T. Edwards
Summary Reasons for performing study: Dantrolene sodium (Dantrium) has been used extensively for the treatment of myopathies in man and anecdotal evidence suggests it is of clinical benefit in the control of exercise-induced rhabdomyolysis (ER) in racehorses, although data to support this are currently lacking. Objectives: To investigate the efficacy of oral dantrolene sodium in controlling ER in a randomised, double-blind, placebo-controlled crossover trial involving 77 Thoroughbred racehorses in Newmarket, UK. Methods: Horses were treated on 2 occasions 1 week apart, with treatment days coinciding with a return to exercise following 2 days box rest on each occasion. For the first treatment, each horse was randomly selected to receive either 800 mg dantrolene sodium or a colour- matched placebo administered orally 1 h before exercise. This was followed by crossover to the other treatment on the second occasion, with each horse thereby acting as its own control. Degree of ER was assessed using rising serum creatine kinase (CK) levels, by subtracting pre-exercise blood CK levels from those measured in 6 h post exercise blood samples. For each horse, the difference in change between pre- and post exercise CK values between placebo and dantrolene treatments was calculated, with positive values indicating a greater rise with placebo than with dantrolene sodium treatment. Results: The overall mean difference for all horses was +104.8 iu/l and the null hypothesis, that there was no true difference in non-normally distributed post exercise rises in CK values between placebo and dantrolene treatments, was rejected (P = 0.0013) using the nonparametric Wilcoxon signed rank test. Additionally, no horses given dantrolene sodium showed clinical signs of ER, whereas 3 horses given the placebo developed ER following exercise. The incidence of ER in the study was 4% (3/77). Conclusions: The results confirmed that oral administration of dantrolene sodium, 1 h before exercise, had a statistically significant effect on reducing the difference between pre - and post exercise plasma CK levels compared with a placebo in the same animals, and preventing clinical ER in susceptible individuals. Potential relevance: This study suggested that dantrolene sodium is of use in controlling ER in the Thoroughbred racehorse. Further investigation into pre- and post exercise myoplasmic calcium levels and the repeat of the study late in the season when horses receive a much higher energy ration and more strenuous exercise would appear to be warranted. [source]

Escherichia coli serogroup O26 , a new look at an old adversary

JOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2008
C. Jenkins
Summary Escherichia coli serogroup O26 played an important part in the early work on Verocytotoxin and is an established diarrhoeal pathogen. Recently, Verocytotoxigenic E. coli (VTEC) O26 has been increasingly associated with diarrhoeal disease and frequently linked to outbreaks and cases of haemolytic uraemic syndrome (HUS). This review investigates the pathogenicity, geographical distribution, changing epidemiology, routes of transmission and improved detection of VTEC O26. Laboratory data on VTEC O26 isolates and clinical data on HUS suggest a true difference in the incidence of VTEC O26 in different geographic locations. However, few diagnostic laboratories use molecular methods to detect VTEC and so it is difficult to assess the role of VTEC O26 in causing diarrhoeal disease. VTEC O26 is frequently found in the cattle population but rarely in food. However, the small number of outbreaks analysed to date are thought to be food-borne rather than associated with direct or indirect contact with livestock or their faeces. The increase in awareness of VTEC O26 in the clinical and veterinary setting has coincided with the development of novel techniques that have improved our ability to detect and characterize this pathogen. [source]

An optimal adaptive design to address local regulations in global clinical trials,

PHARMACEUTICAL STATISTICS: THE JOURNAL OF APPLIED STATISTICS IN THE PHARMACEUTICAL INDUSTRY, Issue 3 2010
Xiaolong Luo
Abstract After multi-regional clinical trials (MRCTs) have demonstrated overall significant effects, evaluation for a region-specific effect is often important. Recent guidance (see, e.g. 1) from regulatory authorities regarding evaluation for possible country-specific effects has led to research on statistical designs that incorporate such evaluations in MRCTs. These statistical designs are intended to use the MRCTs to address the requirements for global registration of a medicinal product. Adding a regional requirement could change the probability for declaring positive effect for the region when there is indeed no treatment difference as well as when there is in fact a true difference within the region. In this paper, we first quantify those probability structures based on the guidance issued by the Ministry of Health, Labour and Welfare (MHLW) of Japan. An adaptive design is proposed to consider those probabilities and to optimize the efficiency for regional objectives. This two-stage approach incorporates comprehensive global objectives into an integrated study design and may mitigate the need for a separate local bridging study. A procedure is used to optimize region-specific enrollment based on an objective function. The overall sample size requirement is assessed. We will use simulation analyses to illustrate the performance of the proposed study design. Copyright © 2010 John Wiley & Sons, Ltd. [source]

The promise of geometric morphometrics

AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue S35 2002
Joan T. Richtsmeier
Abstract Nontraditional or geometric morphometric methods have found wide application in the biological sciences, especially in anthropology, a field with a strong history of measurement of biological form. Controversy has arisen over which method is the "best" for quantifying the morphological difference between forms and for making proper statistical statements about the detected differences. This paper explains that many of these arguments are superfluous to the real issues that need to be understood by those wishing to apply morphometric methods to biological data. Validity, the ability of a method to find the correct answer, is rarely discussed and often ignored. We explain why demonstration of validity is a necessary step in the evaluation of methods used in morphometrics. Focusing specifically on landmark data, we discuss the concepts of size and shape, and reiterate that since no unique definition of size exists, shape can only be recognized with reference to a chosen surrogate for size. We explain why only a limited class of information related to the morphology of an object can be known when landmark data are used. This observation has genuine consequences, as certain morphometric methods are based on models that require specific assumptions, some of which exceed what can be known from landmark data. We show that orientation of an object with reference to other objects in a sample can never be known, because this information is not included in landmark data. Consequently, a descriptor of form difference that contains information on orientation is flawed because that information does not arise from evidence within the data, but instead is a product of a chosen orientation scheme. To illustrate these points, we apply superimposition, deformation, and linear distance-based morphometric methods to the analysis of a simulated data set for which the true differences are known. This analysis demonstrates the relative efficacy of various methods to reveal the true difference between forms. Our discussion is intended to be fair, but it will be obvious to the reader that we favor a particular approach. Our bias comes from the realization that morphometric methods should operate with a definition of form and form difference consistent with the limited class of information that can be known from landmark data. Answers based on information that can be known from the data are of more use to biological inquiry than those based on unjustifiable assumptions. Yrbk Phys Anthropol 45:63,91, 2002. © 2002 Wiley-Liss, Inc. [source]

Growth response of Nile tilapia fry to salinity stress in the presence of an ,internal reference' fish

AQUACULTURE RESEARCH, Issue 7 2005
Zubaida U Basiao
Abstract Growth of three strains of Oreochromis niloticus L. fry exposed to salinity stress in the presence of an internal reference fish were compared. The Central Luzon State University (CLSU) strain was obtained from the Freshwater Aquaculture Center, CLSU, Philippines. The ISRAEL strain was acquired from the Philippine government's Bureau of Fisheries and Aquatic Resources National Freshwater Fisheries Technology Center (BFAR-NFFTC), Munoz, Nueva Ecija. The National Inland Fisheries Institute (NIFI) strain was obtained from the NIFI, Bangkok, Thailand. Eight to nine full-sib families (replicates) per strain were split into two groups. One group was grown in freshwater for 2 weeks, acclimated to 32 ppt and reared for 2 weeks and finally grown in freshwater for another 2 weeks. Another group was contemporaneously grown in freshwater polyethylene tanks for 6 weeks. Each replicate family included a size-matched internal reference population of red tilapia strain. Two-way analysis of variance (anova) revealed no significant strain differences (P=0.081; r2=0.106). However, analysis of covariance with the internal reference strain used as a covariate showed significant (P=0.049; r2=0.638) strain effects on specific growth (based on standard length measurements). The ISRAEL strain showed consistently better growth rate in both saline and freshwater environments than the NIFI and CLSU strains. We estimated the statistical power of the two-way anova (,=,(k,,1)(factor MS,s2)/(k,s2); Zar 1984) to be ,0.30. There was a 70% probability of a Type II error and no true difference in the growth of the three strains was detected. The use of internal reference strain as a covariate improved the r2 from 0.106 to 0.638 and increased the efficiency of the test in detecting a true difference. Other strain comparison studies in our laboratory at the Southeast Asian Fisheries Development Center Aquaculture Department showed that the ISRAEL strain shows better growth than the NIFI and CLSU strains in a crowding stress tolerance experiment, when fed only with rice bran and under restrictive feeding regimes. [source]

Magnification devices for endodontic therapy

AUSTRALIAN DENTAL JOURNAL, Issue 4 2009
M Del Fabbro
Background:, After the introduction of microsurgical principles in endodontics, involving new techniques for root canal treatment, there has been a continuous search for enhancing the visualization of the surgical field. It would be interesting to know if the technical advantages for the operator brought in by magnification devices like surgical microscope, endoscope and magnifying loupes, are also associated with advantages for the patient, in terms of improvement of clinical and radiographic outcomes. Objectives:, The purpose of this systematic review was to evaluate and compare the effects of endodontic treatment performed with the aid of magnification devices versus endodontic treatment without magnification devices. We also aimed at comparing among them the different magnification devices used in endodontics (microscope, endoscope, magnifying loupes). Search strategy:, The Cochrane Oral Health Group Trials Register, CENTRAL, MEDLINE and EMBASE were searched with appropriate search strategies. Handsearching included nine dental journals. The bibliographies of relevant clinical trials and relevant articles were checked for identifying studies outside the handsearched journals. Seven manufacturers of instruments in the field of endodontics and/or endodontic surgery, as well as the authors of the identified randomized controlled trials (RCTs) were contacted in order to identify unpublished or ongoing RCTs. There were no language restrictions. The last electronic search was conducted on 2nd April 2009, and the last handsearching was undertaken on 31st January 2009. Selection criteria:, All randomized and quasi-randomized trials comparing endodontic therapy performed with or without using one or more types of magnification device, as well as randomized and quasi-randomized trials comparing two or more magnification devices used as an adjunct to endodontic therapy were considered. Data collection and analysis:, Screening of studies and data extraction were conducted independently and in duplicate. The Cochrane Collaboration statistical guidelines were to be followed for data synthesis. Main results:, No trial could be included in the present review. All of the prospective trials that were identified, all dealing with endodontic surgery, had to be excluded for various reasons. Only one RCT was identified comparing three magnificators (magnifying loupes, surgical microscope, endoscope) in endodontic surgery. No RCT was found that compared the outcome of endodontic therapy using or without using a given magnification device. Authors' conclusions:, No objective conclusion can be drawn from the results of this review as no article was identified in the current literature that satisfied the criteria for inclusion. It is unknown if and how the type of magnification device affects the treatment outcome, considering the high number of factors that may have a significant impact on the success of endodontic surgical procedure. This should be investigated by further long-term RCTs with large sample size. Technical advantages of magnificators have been widely reported in low evidence level studies, but they should be systematically addressed to know if there can be the clinical indication for using a given magnification device for specific clinical situations, such as for molar teeth, or if they can all be used interchangeably. Well-designed RCTs should also be performed to determine the true difference in terms of treatment success rates between using or not using a magnification device in both conventional and surgical endodontic treatment, if any exist. Plain language summary:, Magnification devices for endodontic therapy. There are no data to draw a sound conclusion on the effect of adopting either a microscope, an endoscope, or magnifying loupes for better visualization in endodontic therapy, in terms of clinical outcomes. Though the use of magnification devices has often been associated with technical advantages for the operator and with an improved management of the root canal due to a better visualization of the operative field, it still has to be demonstrated that their use may lead to an improved treatment success rate. More long-term well-designed randomized trials with a large sample size are urgently needed to address the issues of the present review. [source]

Methods for incorporating covariate adjustment, subgroup analysis and between-centre differences into cost-effectiveness evaluations

HEALTH ECONOMICS, Issue 12 2005
Richard M. Nixon
Abstract Background: Overall assessments of cost,effectiveness are now commonplace in informing medical policy decision making. It is often important, however, also to investigate how cost,effectiveness varies between patient subgroups. Yet such analyses are rarely undertaken, because appropriate methods have not been sufficiently developed. Methods: We propose a coherent set of Bayesian methods to extend cost,effectiveness analyses to adjust for baseline covariates, to investigate differences between subgroups, and to allow for differences between centres in a multicentre study using a hierarchical model. These methods consider costs and effects jointly, and allow for the typically skewed distribution of cost data. The results are presented as inferences on the cost,effectiveness plane, and as cost,effectiveness acceptability curves. Results: In applying these methods to a randomised trial of case management of psychotic patients, we show that overall cost,effectiveness can be affected by ignoring the skewness of cost data, but that it may be difficult to gain substantial precision by adjusting for baseline covariates. While analyses of overall cost,effectiveness can mask important subgroup differences, crude differences between centres may provide an unrealistic indication of the true differences between them. Conclusions: The methods developed allow a flexible choice for the distributions used for cost data, and have a wide range of applicability , to both randomised trials and observational studies. Experience needs to be gained in applying these methods in practice, and using their results in decision making. Copyright © 2005 John Wiley & Sons, Ltd. [source]

A COMPARISON OF THE EFFECTIVENESS OF HEDONIC SCALES AND END-ANCHOR COMPRESSION EFFECTS

JOURNAL OF SENSORY STUDIES, Issue 2010
HARRY T. LAWLESS
ABSTRACT Three experiments were conducted to compare the relative performance of hedonic scaling methods, including the labeled affective magnitude (LAM) scale. In the first study, three versions of the LAM were used to evaluate 20 phrases that described diverse sensory experiences. One scale was anchored to "greatest imaginable like/dislike for any experience" and another used the "greatest imaginable like" phrase of the LAM but with the interior phrases repositioned relative to "any experience." The scale anchored to "any experience" showed a smaller range of scale usage and lower statistical differentiation, relative to the LAM scale, with the repositioned scale intermediate. Two further experiments compared the LAM to the nine-point hedonic scale, an 11-point category scale using the LAM phrases, and to a three-label line scale, a simplified version of the LAM with only the end phrases and the neutral center-point phrase. All scales showed similar differentiation of juices in the second study and sensory experience phrases in the third. A modest advantage for the LAM scale in the second experiment did not extend to the third study. Researchers should be careful in the choice of high end anchors for hedonic scales, as a compressed range of scale usage may result in lower product differentiation. PRACTICAL APPLICATIONS Hedonic scales for food acceptability are widely used in new product development for consumer testing and in food preference surveys. A desired goal of efficient sensory evaluation testing is the ability of tests to differentiate samples on the basis of scale data, in this case scales commonly used for food acceptability and preference testing. Scales which are able to differentiate products more effectively are less likely to lead to Type II error in experimentation, in which true differences between products are not detected. Such errors can lead to lost opportunities for product improvements or to enhanced chances for taking undetected risks in the case of false parity conclusions. [source]

The reliability and validity of a matrix to assess the completed reflective personal development plans of general practitioners

MEDICAL EDUCATION, Issue 4 2006
Chris Roberts
Introduction, We wished to determine whether assessors could make reliable and valid judgements about the quality of completed reflective personal development plans (PDPs) for the purpose of accrediting UK general practitioners (GPs) for a postgraduate education allowance using a marking matrix, and secondly, to plan a feasible model of PDP assessment in the context of forthcoming GP appraisal/revalidation that would overcome the main sources of error identified from this study. Methods, Within generalisability theory, a variance components analysis on PDP scores estimated reliability and the effect on them of varying, for example, the number of assessors. We investigated the construct validity of the matrix through its internal consistency and detection of differences in the quality of PDPs. Results, For a single PDP and one assessor, 37.6% of the variance in scores was due to true differences in the quality of the PDP. Between 5 and 7 PDP assessors are needed to achieve summative reliability of greater than 0.8. While increasing the number of judges is important, reliability could also be improved by addressing assessor subjectivity. Construct validity was demonstrated, as the matrix distinguished between good, satisfactory and poor PDPs, and it had good internal consistency. Conclusion, PDP assessment has reasonable summative characteristics for the purpose of assessing GPs' reflective continuing professional development. If doctors could include their PDPs within their revalidation folders as evidence of their reflections on pursuing better clinical performance, we have described a reliable, valid and feasible method of external assessment. [source]