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Limited Sample Size (limited + sample_size)
Selected AbstractsThe Multicenter Study of Epilepsy Surgery: Recruitment and Selection for SurgeryEPILEPSIA, Issue 11 2003Anne T. Berg Summary:,Purpose: Multiple studies have examined predictors of seizure outcomes after epilepsy surgery. Most are single-center series with limited sample size. Little information is available about the selection process for surgery and, in particular, the proportion of patients who ultimately have surgery and the characteristics that identify those who do versus those who do not. Such information is necessary for providing the epidemiologic and clinical context in which epilepsy surgery is currently performed in the United States and in other developed countries. Methods: An observational cohort of 565 surgical candidates was prospectively recruited from June 1996 through January 2001 at six Northeastern and one Midwestern surgical centers. Standardized eligibility criteria and protocol for presurgical evaluations were used at all seven sites. Results: Three hundred ninety-six (70%) study subjects had resective surgery. Clinical factors such as a well-localized magnetic resonance imaging (MRI) abnormality and consistently localized EEG findings were most strongly associated with having surgery. Of those who underwent intracranial monitoring (189, 34%), 85% went on to have surgery. Race/ethnicity and marital status were marginally associated with having surgery. Age, education, and employment status were not. Demographic factors had little influence over the surgical decision. More than half of the patients had intractable epilepsy for ,10 years and five or more drugs had failed by the time they initiated their surgical evaluation. During the recruitment period, eight new antiepileptic drugs were approved by the Food and Drug Administration for use in the United States and came into increasing use in this study's surgical candidates. Despite the increased availability of new therapeutic options, the proportion that had surgery each year did not fluctuate significantly from year to year. This suggests that, in this group of patients, the new drugs did not provide a substantial therapeutic benefit. Conclusions: Up to 30% of patients who undergo presurgical evaluations for resective epilepsy surgery ultimately do not have this form of surgery. This is a group whose needs are not currently met by available therapies and procedures. Lack of clear localizing evidence appears to be the main reason for not having surgery. To the extent that these data can address the question, they suggest that repeated attempts to control intractable epilepsy with new drugs will not result in sustained seizure control, and eligible patients will proceed to surgery eventually. This is consistent with recent arguments to consider surgery earlier rather than later in the course of epilepsy. Postsurgical follow-up of this group will permit a detailed analysis of presurgical factors that predict the best and worst seizure outcomes. [source] Does contact dermatitis to fragrances influence the quality of life?FLAVOUR AND FRAGRANCE JOURNAL, Issue 4 2009A descriptive study measuring, comparing the quality of life, skin involvement in patients with contact dermatitis to fragrances Abstract The study of the impact of diseases on individuals' quality of life is an important and useful tool for clinicians, particularly for an efficient follow-up and for the good management of patients suffering from chronic diseases. Contact dermatitis is a common condition in dermatological patients. However, despite efficient screening, the understanding and acceptance of contact allergy remain difficult and avoidance of these allergens is not always possible. The aim of this study was to determine whether contact dermatitis to fragrances affects quality of life and to define whether there is a relationship between the severity of skin involvement and quality of life. To measure the quality of life, we chose the VQ-Dermato (VQ-d) questionnaire, the only valid and reliable questionnaire in French, to which we added 10 non-validated specific questions regarding fragrances. We included patients with pertinent positive patch test reactions to fragrances attending the contact clinic between 1 January 1998 and 30 September 2004. During this time, 2814 patients were patch tested and 310 had positive reactions to the fragrance mix 8% (FM) of the standard series. We recruited non-atopic individuals, exclusively allergic to fragrance mix, with patch test reactions scored ++ and +++; the only additional positive reactions accepted were to balsam of Peru and the patient's own perfumes; 52 patients met these criteria, but only 33 participated. To evaluate the severity of skin involvement, we used the severity scoring of atopic dermatitis (SCORAD index). The quality of life of individuals allergic to fragrances was mostly moderately affected. Patients were more affected psychologically during the first year after the diagnosis of fragrance allergy. Skin reaction during the acute stage of contact allergy to fragrances can be severe. No correlation between VQ-d and SCORAD could be established. It was concluded that there was no severe impact on quality of life because of fragrance contact allergy, but that psychological issues and depression may play an important role in determining the way skin disease affects people. Patch testing improves the quality of life. Lack of correlation between VQ-d and SCORAD demonstrates that an objective measure such as SCORAD may not fully capture the impact of the disease. These results cannot be generalized because of the low response rate and limited sample size. Copyright © 2009 John Wiley & Sons, Ltd. [source] Quantification and correction of bias in tagging SNPs caused by insufficient sample size and marker density by means of haplotype-dropping,GENETIC EPIDEMIOLOGY, Issue 1 2008Mark M. Iles Abstract Tagging single nucleotide polymorphisms (tSNPs) are commonly used to capture genetic diversity cost-effectively. It is important that the efficacy of tSNPs is correctly estimated, otherwise coverage may be inadequate and studies underpowered. Using data simulated under a coalescent model, we show that insufficient sample size can lead to overestimation of tSNP efficacy. Quantifying this we find that even when insufficient marker density is adjusted for, estimates of tSNP efficacy are up to 45% higher than the true values. Even with as many as 100 individuals, estimates of tSNP efficacy may be 9% higher than the true value. We describe a novel method for estimating tSNP efficacy accounting for limited sample size. The method is based on exclusion of haplotypes, incorporating a previous adjustment for insufficient marker density. We show that this method outperforms an existing Bootstrap approach. We compare the efficacy of multimarker and pairwise tSNP selection methods on real data. These confirm our findings with simulated data and suggest that pairwise methods are less sensitive to sample size, but more sensitive to marker density. We conclude that a combination of insufficient sample size and overfitting may cause overestimation of tSNP efficacy and underpowering of studies based on tSNPs. Our novel method corrects much of this bias and is superior to a previous method. However, sample sizes larger than previously suggested may be required for accurate estimation of tSNP efficacy. This has obvious ramifications for tSNP selection both in candidate regions and using HapMap or SNP chips for genomewide studies. Genet. Epidemiol. 31, 2007. © 2007 Wiley-Liss, Inc. [source] A novel method of comparing the healing properties of two hydrogels in chronic leg ulcersJOURNAL OF THE EUROPEAN ACADEMY OF DERMATOLOGY & VENEREOLOGY, Issue 2 2006M De La Brassinne Abstract Skin ulcers on the legs have a chronic, relapsing course and are often a significant management challenge. Novel methods of measuring and comparing the effects of different treatments can be of assistance in addressing this situation. A clinical pilot study using original methods was undertaken to compare the healing properties of the alginate gel Flaminal® (test) and the hydrocolloid gel Intrasite® (control) on chronic leg ulcers. The study was performed over a period of 28 days with two parallel groups of 10 patients. Both the surface (acetate tracing and planimetry) and the volume (Jeltrate® mould impression and weighting) of each wound were measured at baseline and after 7, 14 and 28 days of treatment. On both parameters results were superior with the test product compared to the control, with volume reduction being the first parameter to change. Between groups, difference in wound volume reduction was detected as early as day 7 whereas difference in surface reduction was clearly apparent only at day 28. Correlation between wound surface and volume reductions was also better in the test group (r = 0.843 vs. 0.421) than in the control. In conclusion, this pilot study suggests that combining wound surface and volume evaluations allows a more precise analysis of the healing process in venous leg ulcers and that this method is able to detect very early differences in treatments even with limited sample size. [source] Fine-scale genetic structure and gene dispersal inferences in 10 Neotropical tree speciesMOLECULAR ECOLOGY, Issue 2 2006OLIVIER J. HARDY Abstract The extent of gene dispersal is a fundamental factor of the population and evolutionary dynamics of tropical tree species, but directly monitoring seed and pollen movement is a difficult task. However, indirect estimates of historical gene dispersal can be obtained from the fine-scale spatial genetic structure of populations at drift,dispersal equilibrium. Using an approach that is based on the slope of the regression of pairwise kinship coefficients on spatial distance and estimates of the effective population density, we compare indirect gene dispersal estimates of sympatric populations of 10 tropical tree species. We re-analysed 26 data sets consisting of mapped allozyme, SSR (simple sequence repeat), RAPD (random amplified polymorphic DNA) or AFLP (amplified fragment length polymorphism) genotypes from two rainforest sites in French Guiana. Gene dispersal estimates were obtained for at least one marker in each species, although the estimation procedure failed under insufficient marker polymorphism, limited sample size, or inappropriate sampling area. Estimates generally suffered low precision and were affected by assumptions regarding the effective population density. Averaging estimates over data sets, the extent of gene dispersal ranged from 150 m to 1200 m according to species. Smaller gene dispersal estimates were obtained in species with heavy diaspores, which are presumably not well dispersed, and in populations with high local adult density. We suggest that limited seed dispersal could indirectly limit effective pollen dispersal by creating higher local tree densities, thereby increasing the positive correlation between pollen and seed dispersal distances. We discuss the potential and limitations of our indirect estimation procedure and suggest guidelines for future studies. [source] Environmental risk factors for early infantile atopic dermatitisPEDIATRIC ALLERGY AND IMMUNOLOGY, Issue 5 2007I. J. Wang Previous studies of predictors of atopic dermatitis (AD) in Asia have had limited sample size and small numbers of variables focused primarily on family history or dietary exposures. The purpose of this study was to evaluate the influence of various environmental risk factors for early infantile AD. We used multistage, stratified systematic sampling to recruit 2048 mother,child pairs from the Taiwan national birth registration in 2003. Information on environmental risk factors for infant AD gathered by questionnaire were available from 1760 infants at 6 months of age. Multiple logistic regression was used to estimate adjusted odds ratios (aORs) and their 95% confidence intervals (CIs) for risk factors for AD after adjusting for potential confounders. AD was noted in 118 of 1760 (6.7%) of the infants. After adjusting for maternal age and education, family history of atopy, infant gender, and gestational age, fungi on walls of the house [aOR 2.14 (95% CI 1.41,3.22)] and frequent use of microwave oven at home [aOR 1.71 (95% CI 1.13,2.58)] increased the risk of early infantile AD. This study suggests that environmental factors do play a role in early infantile AD. Fungi, a kind of aeroallergen, are especially important in humid climate as in Taiwan and their impacts might be felt at the early infant stage. The hazards of microwave use should be paid more attention. [source] ORIGINAL RESEARCH,EPIDEMIOLOGY: Effect of Sexual Function on Health-Related Quality of Life Mediated by Depressive Symptoms in Cardiac Rehabilitation.THE JOURNAL OF SEXUAL MEDICINE, Issue 6 2010Findings of the SPARK Project in 493 Patients ABSTRACT Introduction., Empirical evidence suggests associations between cardiovascular diseases, sexual functioning, depressive symptoms, and quality of life. However, to date, the interrelation of these constructs has not been examined simultaneously in a structural analysis. Aim., To estimate the prevalence of sexual disorders and depressive symptoms and to examine the association between sexual disorders, depressive symptoms, and quality of life in patients in the rehabilitation of cardiovascular disorders. Aim., A postal survey in five German inpatient rehabilitation centers for cardiovascular diseases was conducted. Prevalence of sexual disorders and depressive symptoms were assessed using psychometrically sound instruments. To analyze complex associations, structural equation modeling was used. Main Outcome Measures., For epidemiological questions, proportions with 95% confidence intervals were calculated. The strength of association in structural equation models was expressed as a standardized regression coefficient. Results., Data from 493 patients were analyzed (response rate 22.7%). At least moderate erectile dysfunction proved to be present in 20.3% of men. The prevalence of female sexual dysfunction lay at 43.1%. At least moderate depressive symptoms were present in 14.4% of men and 16.5% of women. A considerable association between sexual functioning and quality of life was found in both sexes, which was largely mediated by depressive symptoms. Major drawbacks of the study are imprecision of the estimates due to limited sample size and questionable generalizability of the findings due to possible self-selection bias. Conclusions., Considering the high prevalence of depressive symptoms and their role as a mediating factor between sexual functioning and quality of life, it is recommended to routinely screen for depression in men and women with cardiac disease. Kriston L, Günzler C, Agyemang A, Bengel J, and Berner MM. Effect of sexual function on health-related quality of life mediated by depressive symptoms in cardiac rehabilitation. Findings of the SPARK project in 493 patients. J Sex Med 2010;7:2044,2055. [source] Gene polymorphisms and prostate cancer: the evidenceBJU INTERNATIONAL, Issue 11 2009Seyed S. Dianat OBJECTIVE Prostate cancer is still the most frequent noncutaneous male malignancy and is the second most common cause of cancer death. Genetic factors have been extensively studied in different countries. In addition, numerous genome,wide association studies have been performed in developed countries. Genetic tests will be applied in the near future for diagnosis, therapeutic, and prognostic significance. Therefore, we reviewed the association of several important pathways and genes with critical functions in prostate cancer development or progression. MATERIALS AND METHODS We performed a PubMed® search using several key words such as prostate cancer, names of important genes with critical function, and polymorphisms. Then, we reviewed retrieved articles as well as relevant articles from 1997 to 2009. RESULTS There are conflicting results of studies on some gene polymorphisms in association with prostate cancer. Most of the inconsistent results have been reported in studies investigating the vitamin D receptor gene polymorphism in association with prostate cancer. Genes related to angiogenesis and cell adhesion genes are more promising. Following results of future studies, the use of antibodies blocking over-expressed genes or proteins may be supported in patients with prostate cancer. CONCLUSIONS The difference between the results of studies on gene polymorphisms in prostate cancer may be explained partly by ethnic differences, limited sample size, and other risk or protective factors modifying these effects. Genome-wide studies are currently performed in developed countries and extensive use of this type of analysis may merit consideration in other countries. Furthermore, future studies are needed to further investigate environmental and diet factors interactions with genetic factors. [source] Cryptic variation in butterfly eyespot development: the importance of sample size in gene expression studiesEVOLUTION AND DEVELOPMENT, Issue 1 2007Robert D. Reed SUMMARY Previous studies have shown that development can be robust to variation in parameters such as the timing or level of gene expression. This leads to the prediction that natural populations should be able to host developmental variation that has little phenotypic effect. Cryptic variation is of particular interest because it can result in selectable phenotypes when "released" by environmental or genetic factors. Currently, however, we have little idea of how variation is distributed between genes or over time in pattern formation processes. Here we survey expression of Notch (N), Spalt (Sal), and Engrailed (En) during butterfly eyespot determination to better understand how pattern formation may vary within a population. We observed substantial heterochronic variance in the progress of spatial expression patterns for all three proteins, suggesting some degree of developmental buffering in eyespot development. Peak variance for different proteins was found at both early and late stages of development, contrasting with previous models suggesting that the distribution of variance should be more temporally focused during pattern formation. We speculate that our observations are representative of a standing reservoir of cryptic variation that may contribute to phenotypic evolution under certain circumstances. Our results also provide a strong cautionary message that gene expression studies with limited sample sizes can be positively misleading in terms of inferring expression pattern time series, as well as for making cross-species phylogenetic comparisons. [source] Use of the 1-mm micro-probe for metabolic analysis on small volume biological samplesJOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 8b 2009Natalie J. Serkova Abstract Endogenous metabolites are promising diagnostic end-points in cancer research. Clinical application of high-resolution NMR spectroscopy is often limited by extremely low volumes of human specimens. In the present study, the use of the Bruker 1-mm high-resolution TXI micro-probe was evaluated in the elucidation of metabolic profiles for three different clinical applications with limited sample sizes (body fluids, isolated cells and tissue biopsies). Sample preparation and 1H-NMR metabolite quantification protocols were optimized for following oncology-oriented applications: (i) to validate the absolute concentrations of citrate and spermine in human expressed prostatic specimens (EPS volumes 5 to 10 ,l: prostate cancer application); (ii) to establish the metabolic profile of isolated human lymphocytes (total cell count 4 = 106: chronic myelogenous leukaemia application); (iii) to assess the metabolic composition of human head-and-neck cancers from mouse xenografts (biopsy weights 20 to 70 mg: anti-cancer treatment application). In this study, the use of the Bruker 1-mm micro-probe provides a convenient way to measure and quantify endogenous metabolic profiles of samples with a very low volume/weight/cell count. [source] Amniotomy for Shortening Spontaneous LabourBIRTH, Issue 2 2001W.D. Fraser A substantive amendment to this systematic review was last made on 25 June 1999. Cochrane reviews are regularly checked and updated if necessary. ABSTRACT Background: Early amniotomy has been advocated as a component of the active management of labour. Several randomised trials comparing routine amniotomy to an attempt to conserve the membranes have been published. Their limited sample sizes limit their ability to address the effects of amniotomy on indicators of maternal and neonatal morbidity. Objectives: To study the effects of amniotomy on the rate of Cesarean delivery and on other indicators of maternal and neonatal morbidity (Apgar less than 7 at 5 minutes, admission to NICU). Search strategy: The register of clinical trials maintained and updated by the Cochrane Pregnancy and Childbirth Group. Selection criteria: All acceptably controlled trials of amniotomy during first stage of labour were eligible. Data collection and analysis: Data were extracted by two trained reviewers from published reports. Trials were assigned methodological quality scores based on a standardised rating system. Typical odds ratios (ORs) were calculated using Peto's method. Main results: Amniotomy was associated with a reduction in labour duration of between 60 and 120 minutes. There was a marked trend toward an increase in the risk of Cesarean delivery: OR = 1.26; 95% Confidence Interval (CI) = 0.96,1.66. The likelihood of a 5-minute Apgar score less than 7 was reduced in association with early amniotomy (OR = 0.54; 95% CI = 0.30,0.96). Groups were similar with respect to other indicators of neonatal status (arterial cord pH, NICU admissions). There was a statistically significant association of amniotomy with a decrease in the use of oxytocin: OR = 0.79; 95% CI = 0.67,0.92. Reviewers' conclusions: Routine early amniotomy is associated with both benefits and risks. Benefits include a reduction in labour duration and a possible reduction in abnormal 5-minute Apgar scores. The meta-analysis provides no support for the hypothesis that routine early amniotomy reduces the risk of Cesarean delivery. Indeed there is a trend toward an increase in Cesarean section. An association between early amniotomy and Cesarean delivery for fetal distress is noted in one large trial. This suggests that amniotomy should be reserved for women with abnormal labour progress. Citation: Fraser WD, Turcot L, Krauss I, Brisson-Carrol G. Amniotomy for shortening spontaneous labour (Cochrane Review). In: The Cochrane Library, 1, 2001. Oxford: Update Software. MeSH: Amnion/*surgery; Cesarean Section; Female; Human; *Labor; Labor Complications/*prevention & control; Pregnancy The preceding reports are abstracts of regularly updated, systematic reviews prepared and maintained by the Cochrane Collaboration. The full text of the reviews are available in The Cochrane Library (ISSN 1464-780X). The Cochrane Library is prepared and published by Update Software Ltd. All rights reserved. See www.update-software.com or contact Update Software, info@update.co.uk, for information on subscribing to The Cochrane Library in your area. Update Software Ltd, Summertown Pavilion, Middle Way, Oxford OX2 7LG, United Kingdom. (Tel: +44 1865 513902; Fax: +44 1865 516918). [source] | |||||||||||||