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‣ Produção científica publicada nos Anais Brasileiros de Dermatologia (2003-2007); Scientific research published on the Anais Brasileiros de Dermatologia (2003-2007)

FERNANDES, Juliana Dumet; MACHADO, Maria Cecília Rivitti; OLIVEIRA, Zilda Najjar Prado de
Fonte: Sociedade Brasileira de Dermatologia Publicador: Sociedade Brasileira de Dermatologia
Tipo: Artigo de Revista Científica
Português
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FUNDAMENTOS - A produção científica da dermatologia brasileira, quantitativa e qualitativamente, é pouco conhecida e pouco estudada. OBJETIVO - Analisar características da produção científica da dermatologia brasileira segundo o publicado nos Anais Brasileiros de Dermatologia entre 2003 e 2007. MÉTODOS - Realizou-se estudo transversal através análise dos artigos publicados nas seções de "investigação clínica, epidemiológica, laboratorial e terapêutica"; "caso clínico"e "comunicação"dos Anais Brasileiros de Dermatologia entre 2003 e 2007. As variáveis de interesse foram: objeto temático, delineamento utilizado e grupo de enfermidades nas seções de investigação e caso clínico e o enfoque quanto à seção "comunicação". RESULTADOS - Entre os artigos de investigação predominaram os trabalhos clínicos (60,3%); os com temática cirúrgica ou cosmiátrica somaram 13%. Delineamento descritivo/observacional prevaleceu (81,9%), sendo a "série de casos"o mais utilizado (50%). Predominaram enfermidades infecciosas (33,6%) entre os de investigação e inflamatórias (28,6%) entre os casos relatados. Relato de casos (54,3%) foi o principal enfoque dado às comunicações CONCLUSÃO - Predominou a tradição descritiva nos artigos publicados no período. Delineamentos mais elaborados e sofisticados foram incomuns. O método científico e a análise crítica da literatura devem fazer parte do currículo da pós-graduação em dermatologia...

‣ Avaliação microbiológica e epidemiológica de cepas do complexo Burkholderia cepacia isoladas de pacientes com fibrose cística; Microbiologic and epidemiologic evaluation of Burkholderia cepacia complex strains isolated from cystic fibrosis patients

Martins, Kátia Maia
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 16/03/2007 Português
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Introdução: Patógenos emergentes são isolados nas vias respiratórias de pacientes com fibrose cística (FC), entre eles a Burkholderia cepacia. Atualmente, é conhecida como um conjunto de nove espécies relacionadas ("genomovares"), referidas coletivamente como complexo B. cepacia. A identificação fenotípica do complexo B. cepacia é difícil, e métodos de análise do genoma bacteriano, como a reação em cadeia da polimerase, que exploram diferenças no gene recA, têm mostrado grande eficácia na caracterização dos genomovares. Alguns Centros de tratamento de FC demonstraram infecções cruzadas entre os pacientes e marcadores de virulência foram identificados com freqüência em alguns deles. Métodos baseados em biologia molecular são capazes de realizar a genotipagem das cepas e têm sido utilizados na avaliação epidemiológica. Objetivos: Identificar o genomovar e a presença de marcadores de virulência entre as cepas do complexo Burkholderia cepacia isoladas de pacientes com fibrose cística atendidos no ICr e analisar as cepas do complexo Burkholderia cepacia através de genotipagem pela técnica de RAPD. Métodos: Foram coletadas 672 amostras de escarro e esfregaço de orofaringe de 140 pacientes com fibrose cística (6 meses a 19 anos) atendidos na nossa Unidade nos períodos de set/2000 a abr/2001 e jun/2003 a jun/2004. As amostras foram cultivadas em meios seletivos...

‣ Methodological adequacy of articles published in two open-access Brazilian cardiology periodicals

Macedo,Cristiane Rufino; Silva,Davi Leite da; Puga,Maria Eduarda
Fonte: Associação Paulista de Medicina - APM Publicador: Associação Paulista de Medicina - APM
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2010 Português
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CONTEXT AND OBJECTIVE: The use of rigorous scientific methods has contributed towards developing scientific articles of excellent methodological quality. This has made it possible to promote their citation and increase the impact factor. Brazilian periodicals have had to adapt to certain quality standards demanded by these indexing organizations, such as the content and the number of original articles published in each issue. This study aimed to evaluate the methodological adequacy of two Brazilian periodicals within the field of cardiology that are indexed in several databases and freely accessible through the Scientific Electronic Library Online (SciELO), and which are now indexed by the Web of Science (Institute for Scientific Information, ISI). DESIGN AND SETTING: Descriptive study at Brazilian Cochrane Center. METHODS: All the published articles were evaluated according to merit assessment (content) and form assessment (performance). RESULTS: Ninety-six percent of the articles analyzed presented study designs that were adequate for answering the objectives. CONCLUSIONS: These two Brazilian periodicals within the field of cardiology published methodologically adequate articles, since they followed the quality standards. Thus, these periodicals can be considered both for consultation and as vehicles for publishing future articles. For further analyses...

‣ The Brazilian Football Association (CBF) model for epidemiological studies on professional soccer player injuries

Arliani,Gustavo Goncalves; Belangero,Paulo Santoro; Runco,Jose Luiz; Cohen,Moisés
Fonte: Faculdade de Medicina / USP Publicador: Faculdade de Medicina / USP
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2011 Português
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OBJECTIVE: This study aims to establish a national methodological model for epidemiological studies on professional soccer player injuries and to describe the numerous relevant studies previously published on this topic. INTRODUCTION: The risk of injury in professional soccer is high. However, previous studies of injury risk in Brazil and other countries have been characterized by large variations in study design and data collection methods as well as definitions of injury, standardized diagnostic criteria, and recovery times. METHODS: A system developed by the Union of European Football for epidemiological studies on professional soccer players is being used as a starting point to create a methodological model for the Brazilian Football Association. To describe the existing studies on professional soccer player injuries, we developed a search strategy to identify relevant epidemiological studies. We included the Latin American and Caribbean Center on Health Sciences and Medline databases in our study. RESULTS: We considered 60 studies from Medline and 16 studies from the Latin American and Caribbean Center on Health Sciences in the final analysis. Twelve studies were selected for final inclusion in this review: seven from the Latin American and Caribbean Center on Health Sciences and five from Medline. We identified a lack of uniformity in the study design...

‣ Evaluation of Methods for Subtyping Campylobacter jejuni during an Outbreak Involving a Food Handler

Fitzgerald, Collette; Helsel, Leta O.; Nicholson, Mabel A.; Olsen, Sonja J.; Swerdlow, David L.; Flahart, Robert; Sexton, June; Fields, Patricia I.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /07/2001 Português
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In October 1998, the Centers for Disease Control and Prevention (CDC) assisted in an investigation of an outbreak of campylobacteriosis at a school in Salina, Kansas. Twenty-two isolates were submitted from the Kansas state public health laboratory to CDC, 9 associated with the outbreak and 13 epidemiologically unrelated sporadic isolates. Pulsed-field gel electrophoresis (PFGE) using SmaI and SalI was initially used to validate the epidemiologic data. We then tested the ability of other subtyping techniques to distinguish the outbreak-associated isolates from unrelated sporadic isolates. The methods employed were somatic O serotyping, PCR-restriction fragment length polymorphism (RFLP) analysis of flaA, DNA sequence analysis of 582 bp of flaA that included the short variable region (SVR), and sequencing of the entire flaA gene. PFGE was the most discriminatory technique, yielding 11 SmaI and 10 SalI restriction profiles. All outbreak isolates were indistinguishable by PFGE, somatic O serotyping, and sequencing of the 582-bp region of the flaA gene. fla typing by PCR-RFLP grouped one sporadic isolate with the outbreak strain. Analysis of the DNA sequence of a 582-bp segment of flaA produced strain groupings similar to that generated by PCR-RFLP but further differentiated two flaA PCR-RFLP types (with a 1-bp difference in the 582-bp region). Two sporadic strains were distinct by flaA PCR-RFLP but differed only by a single base substitution in the 582-bp region. The entire flaA gene was sequenced from strains differing by a single base pair in the 582-bp region...

‣ Methods for Subtyping and Molecular Comparison of Human Viral Genomes

Arens, Max
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /10/1999 Português
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The development over the past two decades of molecular methods for manipulation of RNA and DNA has afforded molecular virologists the ability to study viral genomes in detail that has heretofore not been possible. There are many molecular techniques now available for typing and subtyping of viruses. The available methods include restriction fragment length polymorphism analysis, Southern blot analysis, oligonucleotide fingerprint analysis, reverse hybridization, DNA enzyme immunoassay, RNase protection analysis, single-strand conformation polymorphism analysis, heteroduplex mobility assay, nucleotide sequencing, and genome segment length polymorphism analysis. The methods have certain advantages and disadvantages which should be considered in their application to specific viruses or for specific purposes. These techniques are likely to become more widely used in the future for epidemiologic studies and for investigations into the pathophysiology of virus infections.

‣ Introducing article-processing charges and inviting "detailed methods sections" articles

Phillips, Carl V
Fonte: BioMed Central Publicador: BioMed Central
Tipo: Artigo de Revista Científica
Publicado em 07/06/2005 Português
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This editorial introduces the use of article-processing charges at Epidemiologic Perspectives & Innovations and reviews that advantages of publishing in an Open Access journal. In addition, it introduces a new type of article the journal hopes to publish, detailed reports of study design or data analysis methods that have been used in health science research. The new type of article is intended to supplement the woefully constrained methods sections in standard research report articles, providing information that better fulfills the goals of scientific publishing.

‣ Priorities for development of research methods in occupational cancer.

Ward, Elizabeth M; Schulte, Paul A; Bayard, Steve; Blair, Aaron; Brandt-Rauf, Paul; Butler, Mary Ann; Dankovic, David; Hubbs, Ann F; Jones, Carol; Karstadt, Myra; Kedderis, Gregory L; Melnick, Ronald; Redlich, Carrie A; Rothman, Nathaniel; Savage, Russell
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /01/2003 Português
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Occupational cancer research methods was identified in 1996 as 1 of 21 priority research areas in the National Occupational Research Agenda (NORA). To implement NORA, teams of experts from various sectors were formed and given the charge to further define research needs and develop strategies to enhance or augment research in each priority area. This article is a product of that process. Focus on occupational cancer research methods is important both because occupational factors play a significant role in a number of cancers, resulting in significant morbidity and mortality, and also because occupational cohorts (because of higher exposure levels) often provide unique opportunities to evaluate health effects of environmental toxicants and understand the carcinogenic process in humans. Despite an explosion of new methods for cancer research in general, these have not been widely applied to occupational cancer research. In this article we identify needs and gaps in occupational cancer research methods in four broad areas: identification of occupational carcinogens, design of epidemiologic studies, risk assessment, and primary and secondary prevention. Progress in occupational cancer will require interdisciplinary research involving epidemiologists...

‣ Pesticides--how research has succeeded and failed in informing policy: DDT and the link with breast cancer.

Wolff, M S
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /09/1995 Português
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Investigation of chemical exposures as possible etiologic factors for breast cancer has not been a research priority in the United States, which is surprising given the evidence from animal studies that environmental chemicals cause cancer and reproductive dysfunction. Study of environmental chemicals has also been indicated by the failure of traditional epidemiologic methods to account for significant proportions of breast cancer incidence with other risk factors. The fact that breast cancer risk is strongly associated with reproductive hormones is a further clue that environmental chemicals should be investigated. In addition to cancer, specific outcomes that need to be explored are reproductive dysfunction, immunotoxicity and neurotoxicity. Policy guiding our research should encourage toxicologic investigations of exposures to environmental chemicals that use state-of-the-art methods to determine exposure and human health effects. Using the approach suggested by John McLachlan, functional toxicology should be used to assess the activity of chemicals with regard to these outcomes. Just as dioxin toxicity can be expressed as toxic equivalents, estrogenic activity, for example, can be characterized in terms of estrogenic equivalents. In addition to the need to undertake this kind of research...

‣ Predicting Outcomes of Hospitalization for Heart Failure Using Logistic Regression and Knowledge Discovery Methods

Phillips, Kirk T.; Street, W. Nick
Fonte: American Medical Informatics Association Publicador: American Medical Informatics Association
Tipo: Artigo de Revista Científica
Publicado em //2005 Português
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The purpose of this study is to determine the best prediction of heart failure outcomes, resulting from two methods -- standard epidemiologic analysis with logistic regression and knowledge discovery with supervised learning/data mining. Heart failure was chosen for this study as it exhibits higher prevalence and cost of treatment than most other hospitalized diseases. The prevalence of heart failure has exceeded 4 million cases in the U.S.. Findings of this study should be useful for the design of quality improvement initiatives, as particular aspects of patient comorbidity and treatment are found to be associated with mortality. This is also a proof of concept study, considering the feasibility of emerging health informatics methods of data mining in conjunction with or in lieu of traditional logistic regression methods of prediction. Findings may also support the design of decision support systems and quality improvement programming for other diseases.

‣ Design and methods in a multi-center case-control interview study.

Hartge, P; Cahill, J I; West, D; Hauck, M; Austin, D; Silverman, D; Hoover, R
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /01/1984 Português
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We conducted a case-control study in ten areas of the United States in which a total of 2,982 bladder cancer patients and 5,782 population controls were interviewed. We employed a variety of existing and new techniques to reduce bias and to monitor the quality of data collected. We review here many of the design elements and field methods that can be generally applied in epidemiologic studies, particularly multi-center interview studies, and explain the reasons for our selection of the methods, instruments, and procedures used.

‣ Occurrence of Strongyloides stercoralis in Yunnan Province, China, and Comparison of Diagnostic Methods

Steinmann, Peter; Zhou, Xiao-Nong; Du, Zun-Wei; Jiang, Jin-Yong; Wang, Li-Bo; Wang, Xue-Zhong; Li, Lan-Hua; Marti, Hanspeter; Utzinger, Jürg
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 31/10/2007 Português
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An estimated 30 million to 100 million people are infected with the parasitic worm Strongyloides stercoralis, the causative agent of strongyloidiasis, and yet this is a neglected tropical disease. The diagnosis of this parasite requires specialized techniques (e.g. Baermann and Koga agar plate method), but these are rarely employed in epidemiologic studies. We assessed the occurrence of S. stercoralis in a rural part of southern Yunnan province, China, and compared different diagnostic methods. At least two stool samples were obtained from 180 randomly selected individuals, and examined with four diagnostic approaches, including the Koga agar plate and the Baermann technique. Twenty-one individuals were infected with S. stercoralis (prevalence: 11.7%). Males were more often infected than females (18.3% versus 6.1%, p = 0.011). Infections were absent in children below the age of 15 years. The Baermann technique showed a higher sensitivity than the Koga agar plate method, and the examination of multiple stool samples improved the diagnostic performances of both methods. The use of a mathematical model suggested a ‘true’ S. stercoralis prevalence of 16.3%. There is a need to further study the epidemiology of strongyloidiasis in other parts of China...

‣ Comparison of tagging single-nucleotide polymorphism methods in association analyses

Goode, Ellen L; Fridley, Brooke L; Sun, Zhifu; Atkinson, Elizabeth J; Nord, Alex S; McDonnell, Shannon K; Jarvik, Gail P; de Andrade, Mariza; Slager, Susan L
Fonte: BioMed Central Publicador: BioMed Central
Tipo: Artigo de Revista Científica
Publicado em 18/12/2007 Português
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Several methods to identify tagging single-nucleotide polymorphisms (SNPs) are in common use for genetic epidemiologic studies; however, there may be loss of information when using only a subset of SNPs. We sought to compare the ability of commonly used pairwise, multimarker, and haplotype-based tagging SNP selection methods to detect known associations with quantitative expression phenotypes. Using data from HapMap release 21 on unrelated Utah residents with ancestors from northern and western Europe (CEPH-Utah, CEU), we selected tagging SNPs in five chromosomal regions using ldSelect, Tagger, and TagSNPs. We found that SNP subsets did not substantially overlap, and that the use of trio data did not greatly impact SNP selection. We then tested associations between HapMap genotypes and expression phenotypes on 28 CEU individuals as part of Genetic Analysis Workshop 15. Relative to the use of all SNPs (n = 210 SNPs across all regions), most subset methods were able to detect single-SNP and haplotype associations. Generally, pairwise selection approaches worked extremely well, relative to use of all SNPs, with marked reductions in the number of SNPs required. Haplotype-based approaches, which had identified smaller SNP subsets, missed associations in some regions. We conclude that the optimal tagging SNP method depends on the true model of the genetic association (i.e....

‣ Comparison of Two Multiple-Locus Variable-Number Tandem-Repeat Analysis Methods for Molecular Strain Typing of Human Brucella melitensis Isolates from the Middle East▿

Tiller, Rebekah V.; De, Barun K.; Boshra, Marie; Huynh, Lynn Y.; Van Ert, Matthew N.; Wagner, David M.; Klena, John; Mohsen, T. S.; El-Shafie, S. S.; Keim, Paul; Hoffmaster, Alex R.; Wilkins, Patricia P.; Pimentel, Guillermo
Fonte: American Society for Microbiology (ASM) Publicador: American Society for Microbiology (ASM)
Tipo: Artigo de Revista Científica
Português
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Brucella species are highly monomorphic, with minimal genetic variation among species, hindering the development of reliable subtyping tools for epidemiologic and phylogenetic analyses. Our objective was to compare two distinct multiple-locus variable-number tandem-repeat analysis (MLVA) subtyping methods on a collection of 101 Brucella melitensis isolates from sporadic human cases of brucellosis in Egypt (n = 83), Qatar (n = 17), and Libya (n = 1). A gel-based MLVA technique, MLVA-15IGM, was compared to an automated capillary electrophoresis-based method, MLVA-15NAU, with each MLVA scheme examining a unique set of variable-number tandem repeats. Both the MLVAIGM and MLVANAU methods were highly discriminatory, resolving 99 and 101 distinct genotypes, respectively, and were able to largely separate genotypes from Egypt and Qatar. The MLVA-15NAU scheme presented higher strain-to-strain diversity in our test population than that observed with the MLVA-15IGM assay. Both schemes were able to genetically correlate some strains originating from the same hospital or region within a country. In addition to comparing the genotyping abilities of these two schemes, we also compared the usability, limitations, and advantages of the two MLVA systems and their applications in the epidemiological genotyping of human B. melitensis strains.

‣ Measuring Taste Impairment in Epidemiologic Studies – The Beaver Dam Offspring Study

Cruickshanks, KJ; Schubert, CR; Snyder, DJ; Bartoshuk, LM; Huang, GH; Klein, BEK; Klein, R; Nieto, FJ; Pankow, JS; Tweed, TS; Krantz, EM; Moy, GS
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /07/2009 Português
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Taste or gustatory function may play an important role in determining diet and nutritional status and therefore indirectly impact health. Yet there have been few attempts to study the spectrum of taste function and dysfunction in human populations. Epidemiological studies are needed to understand the impact of taste function and dysfunction on public health, to identify modifiable risk factors, and to develop and test strategies to prevent clinically significant dysfunction. However, measuring taste function in epidemiological studies is challenging and requires repeatable, efficient methods which can measure change over time. Insights gained from translating laboratory-based methods to a population-based study, the Beaver Dam Offspring Study (BOSS) will be shared. In this study, a generalized labeled magnitude scale (gLMS) method was used to measure taste intensity of filter paper disks saturated with salt, sucrose, citric acid, quinine, or 6-n-propylthiouracil and a gLMS measure of taste preferences was administered. In addition, a portable, inexpensive camera system to capture digital images of fungiform papillae and a masked grading system to measure the density of fungiform papillae were developed. Adult children of participants in the population-based Epidemiology of Hearing Loss Study in Beaver Dam...

‣ Comparability and repeatability of methods for estimating the dietary intake of the heterocyclic amine contaminant 2-amino-1-methyl-6-phenylimidazo[4,5b]pyridine (PhIP)

Deziel, Nicole C.; Buckley, Timothy J.; Sinha, Rashmi; Abubaker, Salahaddhin; Platz, Elizabeth A.; Strickland, Paul T.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
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Inconsistent risk estimates for dietary heterocyclic amine (HCA) exposure and cancers may be due to differences in exposure assessment methods and the associated measurement error. We evaluated repeatability and comparability of intake estimates of the HCA 2-amino-1-methyl-6-phenylimidazo[4,5b]pyridine (PhIP) among two food frequency questionnaire (FFQ) collections, three diary collections, and three measurements of urinary PhIP and its metabolites in thirty-six non-smokers in Baltimore, MD during 2004–2005. Collections spanned ~9 months. Method repeatability was characterized with intraclass correlation coefficients (ICCs). Comparability among methods was assessed with Spearman correlation coefficients. Within-subject variability in PhIP intake was comparably high across all methods (ICCs of 0.20, 0.30, and 0.15 for FFQ, diary, and creatinine-adjusted urinary PhIP, respectively). Mean diary-based PhIP intake and mean urinary PhIP concentration were strongly correlated when restricting the analysis to participants with at least one non-zero diary-based estimate of PhIP intake (n=15, r=0.75, P=0.001), but not in the full study population (n=36, r=0.18, P=0.28). Mean PhIP intake from the FFQ was not associated with that either based on the diary or urinary PhIP separately...

‣ A Review of Spatial Methods in Epidemiology, 2000–2010

Auchincloss, Amy H.; Gebreab, Samson Y.; Mair, Christina; Roux, Ana V. Diez
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /04/2012 Português
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Understanding the impact of place on health is a key element of epidemiologic investigation, and numerous tools are being employed for analysis of spatial health-related data. This review documents the huge growth in spatial epidemiology, summarizes the tools that have been employed, and provides in-depth discussion of several methods. Relevant research articles for 2000–2010 from seven epidemiology journals were included if the study utilized a spatial analysis method in primary analysis (n = 207). Results summarized frequency of spatial methods and substantive focus; graphs explored trends over time. The most common spatial methods were distance calculations, spatial aggregation, clustering, spatial smoothing and interpolation, and spatial regression. Proximity measures were predominant and were applied primarily to air quality and climate science and resource access studies. The review concludes by noting emerging areas that are likely to be important to future spatial analysis in public health.

‣ Comparisons across depression assessment instruments in adolescence and young adulthood: An Item Response Theory study using two linking methods

Olino, Thomas M.; Yu, Lan; McMakin, Dana L.; Forbes, Erika E.; Seeley, John R.; Lewinsohn, Peter M.; Pilkonis, Paul A.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /11/2013 Português
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Item response theory (IRT) methods allow for comparing the utility of instruments based on the range and precision of severity assessed by each instrument. As adolescents and young adults can display rapid increases in depressive symptoms, there is a crucial need to sensitively assess mild elevations of symptoms (as an index of initial risk) and moderate-severe symptoms (as an indicator of treatment disposition). We compare the information assessed by the Beck Depression Inventory (BDI) to the newly developed Patient Reported Outcome Measurement Information System – Depression measure (PROMIS-Depression), and the Center for Epidemiologic Studies – Depression (CES-D) scale. The present work is based on data from two fully independent samples of community adolescents and young adults. One sample completed the BDI and CES-D (n = 1482) and the second sample (n = 673) completed the PROMIS-Depression measure and the CES-D. Using two different IRT-based linking methods, (1) equating based on common items and (2) concurrent calibration methods, analyses revealed that the PROMIS-Depression measure assessed information over the widest range of depressive severity with greatest measurement precision relative to the other instruments. This was true for both the 28-item and 8-item versions of the PROMIS-Depression measure. Findings suggest that the PROMIS-Depression measure assessed depression severity with greatest precision and over the widest severity range of the assessed instruments. However...

‣ Validation Study Methods for Estimating Odds Ratio in 2 × 2 × J Tables When Exposure is Misclassified

Nouri, Bijan; Zare, Najaf; Ayatollahi, Seyyed Mohammad Taghi
Fonte: Hindawi Publishing Corporation Publicador: Hindawi Publishing Corporation
Tipo: Artigo de Revista Científica
Português
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Background. Misclassification of exposure variables in epidemiologic studies may lead to biased estimation of parameters and loss of power in statistical inferences. In this paper, the inverse matrix method, as an efficient method of the correction of odds ratio for the misclassification of a binary exposure, was generalized to nondifferential misclassification and 2 × 2 × J tables. Methods. Simple estimates for predictive values when misclassification is nondifferential are presented. Using them, we estimated the corrected log odds ratio and its variance for 2 × 2 × J tables, using the inverse matrix method. A two-step weighted likelihood method was also developed. Moreover, we compared the matrix and inverse matrix methods to the maximum likelihood (MLE) method using a simulation study. Results. In all situations, the inverse matrix method proved to be more efficient than the matrix method. Matrix and inverse matrix methods for nondifferential situations are more efficient than differential misclassification. Conclusions. Although MLE is optimal among all of the methods, it is computationally difficult and requires programming. On the other hand, the inverse matrix method with a simple closed-form presents acceptable efficiency.

‣ Semiparametric methods for center effect measures based on the ratio of survival functions

He, Kevin; Schaubel, Douglas E.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
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The survival function is often of chief interest in epidemiologic studies of time to an event. We develop methods for evaluating center-specific survival outcomes through a ratio of survival functions. The proposed method assumes a center-stratified additive hazards model, which provides a convenient framework for our purposes. Under the proposed methods, the center effects measure is cast as the ratio of subject-specific survival functions under two scenarios: the scenario in which the subject is treated at center j; and that wherein the subject is treated at a hypothetical center with survival function equal to the population average. The proposed measure reduces to the ratio of baseline survival functions, but is invariant to the choice of baseline covariate level. We derive the asymptotic properties of the proposed estimators, and assess finite-sample characteristics through simulation. The proposed methods are applied to national kidney transplant data.