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BMC Medical Research Methodology

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https://www.readbyqxmd.com/read/28743256/a-comparison-of-multiple-imputation-methods-for-handling-missing-values-in-longitudinal-data-in-the-presence-of-a-time-varying-covariate-with-a-non-linear-association-with-time-a-simulation-study
#1
Anurika Priyanjali De Silva, Margarita Moreno-Betancur, Alysha Madhu De Livera, Katherine Jane Lee, Julie Anne Simpson
BACKGROUND: Missing data is a common problem in epidemiological studies, and is particularly prominent in longitudinal data, which involve multiple waves of data collection. Traditional multiple imputation (MI) methods (fully conditional specification (FCS) and multivariate normal imputation (MVNI)) treat repeated measurements of the same time-dependent variable as just another 'distinct' variable for imputation and therefore do not make the most of the longitudinal structure of the data...
July 25, 2017: BMC Medical Research Methodology
https://www.readbyqxmd.com/read/28728594/implementing-the-efftox-dose-finding-design-in-the-matchpoint-trial
#2
Kristian Brock, Lucinda Billingham, Mhairi Copland, Shamyla Siddique, Mirjana Sirovica, Christina Yap
BACKGROUND: The Matchpoint trial aims to identify the optimal dose of ponatinib to give with conventional chemotherapy consisting of fludarabine, cytarabine and idarubicin to chronic myeloid leukaemia patients in blastic transformation phase. The dose should be both tolerable and efficacious. This paper describes our experience implementing EffTox in the Matchpoint trial. METHODS: EffTox is a Bayesian adaptive dose-finding trial design that jointly scrutinises binary efficacy and toxicity outcomes...
July 20, 2017: BMC Medical Research Methodology
https://www.readbyqxmd.com/read/28728582/basic-parametric-analysis-for-a-multi-state-model-in-hospital-epidemiology
#3
Maja von Cube, Martin Schumacher, Martin Wolkewitz
BACKGROUND: The extended illness-death model is a useful tool to study the risks and consequences of hospital-acquired infections (HAIs). The statistical quantities of interest are the transition-specific hazard rates and the transition probabilities as well as attributable mortality (AM) and the population-attributable fraction (PAF). In the most general case calculation of these expressions is mathematically complex. METHODS: When assuming time-constant hazards calculation of the quantities of interest is facilitated...
July 20, 2017: BMC Medical Research Methodology
https://www.readbyqxmd.com/read/28728577/integrating-data-from-randomized-controlled-trials-and-observational-studies-to-predict-the-response-to-pregabalin-in-patients-with-painful-diabetic-peripheral-neuropathy
#4
Joe Alexander, Roger A Edwards, Alberto Savoldelli, Luigi Manca, Roberto Grugni, Birol Emir, Ed Whalen, Stephen Watt, Marina Brodsky, Bruce Parsons
BACKGROUND: More patient-specific medical care is expected as more is learned about variations in patient responses to medical treatments. Analytical tools enable insights by linking treatment responses from different types of studies, such as randomized controlled trials (RCTs) and observational studies. Given the importance of evidence from both types of studies, our goal was to integrate these types of data into a single predictive platform to help predict response to pregabalin in individual patients with painful diabetic peripheral neuropathy (pDPN)...
July 20, 2017: BMC Medical Research Methodology
https://www.readbyqxmd.com/read/28728549/binomial-outcomes-in-dataset-with-some-clusters-of-size-two-can-the-dependence-of-twins-be-accounted-for-a-simulation-study-comparing-the-reliability-of-statistical-methods-based-on-a-dataset-of-preterm-infants
#5
Odile Sauzet, Janet L Peacock
BACKGROUND: The analysis of perinatal outcomes often involves datasets with some multiple births. These are datasets mostly formed of independent observations and a limited number of clusters of size two (twins) and maybe of size three or more. This non-independence needs to be accounted for in the statistical analysis. Using simulated data based on a dataset of preterm infants we have previously investigated the performance of several approaches to the analysis of continuous outcomes in the presence of some clusters of size two...
July 20, 2017: BMC Medical Research Methodology
https://www.readbyqxmd.com/read/28724350/a-random-effects-meta-analysis-model-with-box-cox-transformation
#6
Yusuke Yamaguchi, Kazushi Maruo, Christopher Partlett, Richard D Riley
BACKGROUND: In a random effects meta-analysis model, true treatment effects for each study are routinely assumed to follow a normal distribution. However, normality is a restrictive assumption and the misspecification of the random effects distribution may result in a misleading estimate of overall mean for the treatment effect, an inappropriate quantification of heterogeneity across studies and a wrongly symmetric prediction interval. METHODS: We focus on problems caused by an inappropriate normality assumption of the random effects distribution, and propose a novel random effects meta-analysis model where a Box-Cox transformation is applied to the observed treatment effect estimates...
July 19, 2017: BMC Medical Research Methodology
https://www.readbyqxmd.com/read/28720094/a-literature-review-of-applied-adaptive-design-methodology-within-the-field-of-oncology-in-randomised-controlled-trials-and-a-proposed-extension-to-the-consort-guidelines
#7
Pankaj Mistry, Janet A Dunn, Andrea Marshall
BACKGROUND: The application of adaptive design methodology within a clinical trial setting is becoming increasingly popular. However the application of these methods within trials is not being reported as adaptive designs hence making it more difficult to capture the emerging use of these designs. Within this review, we aim to understand how adaptive design methodology is being reported, whether these methods are explicitly stated as an 'adaptive design' or if it has to be inferred and to identify whether these methods are applied prospectively or concurrently...
July 18, 2017: BMC Medical Research Methodology
https://www.readbyqxmd.com/read/28716060/nonlinear-joint-models-for-individual-dynamic-prediction-of-risk-of-death-using-hamiltonian-monte-carlo-application-to-metastatic-prostate-cancer
#8
Solène Desmée, France Mentré, Christine Veyrat-Follet, Bernard Sébastien, Jérémie Guedj
BACKGROUND: Joint models of longitudinal and time-to-event data are increasingly used to perform individual dynamic prediction of a risk of event. However the difficulty to perform inference in nonlinear models and to calculate the distribution of individual parameters has long limited this approach to linear mixed-effect models for the longitudinal part. Here we use a Bayesian algorithm and a nonlinear joint model to calculate individual dynamic predictions. We apply this approach to predict the risk of death in metastatic castration-resistant prostate cancer (mCRPC) patients with frequent Prostate-Specific Antigen (PSA) measurements...
July 17, 2017: BMC Medical Research Methodology
https://www.readbyqxmd.com/read/28716047/protocol-adherence-for-continuously-titrated-interventions-in-randomized-trials-an-overview-of-the-current-methodology-and-case-study
#9
F Lauzier, N K Adhikari, A Seely, K K Y Koo, E P Belley-Côté, K E A Burns, D J Cook, F D'Aragon, B Rochwerg, M E Kho, S J W Oczkowksi, E H Duan, M O Meade, A G Day, F Lamontagne
BACKGROUND: The standard definition for protocol adherence is the proportion of all scheduled doses that are delivered. In clinical research, this definition has several limitations when evaluating protocol adherence in trials that study interventions requiring continuous titration. DISCUSSION: Building upon a specific case study, we analyzed a recent trial of a continuously titrated intervention to assess the impact of different definitions of protocol deviations on the interpretation of protocol adherence...
July 17, 2017: BMC Medical Research Methodology
https://www.readbyqxmd.com/read/28716005/clarifying-the-distinction-between-case-series-and-cohort-studies-in-systematic-reviews-of-comparative-studies-potential-impact-on-body-of-evidence-and-workload
#10
Tim Mathes, Dawid Pieper
Distinguishing cohort studies from case series is difficult.We propose a conceptualization of cohort studies in systematic reviews of comparative studies. The main aim of this conceptualization is to clarify the distinction between cohort studies and case series. We discuss the potential impact of the proposed conceptualization on the body of evidence and workload.All studies with exposure-based sampling gather multiple exposures (with at least two different exposures or levels of exposure) and enable calculation of relative risks that should be considered cohort studies in systematic reviews, including non-randomized studies...
July 17, 2017: BMC Medical Research Methodology
https://www.readbyqxmd.com/read/28709406/using-structural-equation-modeling-for-network-meta-analysis
#11
Yu-Kang Tu, Yun-Chun Wu
BACKGROUND: Network meta-analysis overcomes the limitations of traditional pair-wise meta-analysis by incorporating all available evidence into a general statistical framework for simultaneous comparisons of several treatments. Currently, network meta-analyses are undertaken either within the Bayesian hierarchical linear models or frequentist generalized linear mixed models. Structural equation modeling (SEM) is a statistical method originally developed for modeling causal relations among observed and latent variables...
July 14, 2017: BMC Medical Research Methodology
https://www.readbyqxmd.com/read/28709404/accounting-for-treatment-use-when-validating-a-prognostic-model-a-simulation-study
#12
Romin Pajouheshnia, Linda M Peelen, Karel G M Moons, Johannes B Reitsma, Rolf H H Groenwold
BACKGROUND: Prognostic models often show poor performance when applied to independent validation data sets. We illustrate how treatment use in a validation set can affect measures of model performance and present the uses and limitations of available analytical methods to account for this using simulated data. METHODS: We outline how the use of risk-lowering treatments in a validation set can lead to an apparent overestimation of risk by a prognostic model that was developed in a treatment-naïve cohort to make predictions of risk without treatment...
July 14, 2017: BMC Medical Research Methodology
https://www.readbyqxmd.com/read/28705151/cost-and-yield-considerations-when-expanding-recruitment-for-genetic-studies-the-primary-open-angle-african-american-glaucoma-genetics-study
#13
Rebecca Salowe, Laura O'Keefe, Sayaka Merriam, Roy Lee, Naira Khachatryan, Prithvi Sankar, Eydie Miller-Ellis, Amanda Lehman, Victoria Addis, Windell Murphy, Jeffrey Henderer, Maureen Maguire, Joan O'Brien
BACKGROUND: African Americans have been historically under-represented in genetic studies. More research is needed on effective recruitment strategies for this population, especially on approaches that supplement traditional clinic enrollment. This study evaluates the cost and efficacy of four supplemental recruitment methods employed by the Primary Open-Angle African American Glaucoma Genetics (POAAGG) study. METHODS: After enrolling 2304 patients from University of Pennsylvania ophthalmology clinics, the POAAGG study implemented four new recruitment methods to supplement clinic enrollment...
July 14, 2017: BMC Medical Research Methodology
https://www.readbyqxmd.com/read/28705147/sample-size-re-estimation-in-paired-comparative-diagnostic-accuracy-studies-with-a-binary-response
#14
Gareth P J McCray, Andrew C Titman, Paula Ghaneh, Gillian A Lancaster
BACKGROUND: The sample size required to power a study to a nominal level in a paired comparative diagnostic accuracy study, i.e. studies in which the diagnostic accuracy of two testing procedures is compared relative to a gold standard, depends on the conditional dependence between the two tests - the lower the dependence the greater the sample size required. A priori, we usually do not know the dependence between the two tests and thus cannot determine the exact sample size required...
July 14, 2017: BMC Medical Research Methodology
https://www.readbyqxmd.com/read/28697723/implementation-fidelity-of-a-self-management-course-for-epilepsy-method-and-assessment
#15
G Wojewodka, S Hurley, S J C Taylor, A J Noble, L Ridsdale, L H Goldstein
BACKGROUND: Complex interventions such as self-management courses are difficult to evaluate due to the many interacting components. The way complex interventions are delivered can influence the effect they have for patients, and can impact the interpretation of outcomes of clinical trials. Implementation fidelity evaluates whether complex interventions are delivered according to protocol. Such assessments have been used for one-to-one psychological interventions; however, the science is still developing for group interventions...
July 11, 2017: BMC Medical Research Methodology
https://www.readbyqxmd.com/read/28693500/awareness-of-wearing-an-accelerometer-does-not-affect-physical-activity-in-youth
#16
Jérémy Vanhelst, Laurent Béghin, Elodie Drumez, Stéphanie Coopman, Frédéric Gottrand
BACKGROUND: This study aimed to investigate whether awareness of being monitored by an accelerometer has an effect on physical activity in young people. METHODS: Eighty healthy participants aged 10-18 years were randomized between blinded and nonblinded groups. The blinded participants were informed that we were testing the reliability of a new device for body posture assessment and these participants did not receive any information about physical activity. In contrast, the nonblinded participants were informed that the device was an accelerometer that assessed physical activity levels and patterns...
July 11, 2017: BMC Medical Research Methodology
https://www.readbyqxmd.com/read/28693497/inter-rater-reliability-of-amstar-is-dependent-on-the-pair-of-reviewers
#17
Dawid Pieper, Anja Jacobs, Beate Weikert, Alba Fishta, Uta Wegewitz
BACKGROUND: Inter-rater reliability (IRR) is mainly assessed based on only two reviewers of unknown expertise. The aim of this paper is to examine differences in the IRR of the Assessment of Multiple Systematic Reviews (AMSTAR) and R(evised)-AMSTAR depending on the pair of reviewers. METHODS: Five reviewers independently applied AMSTAR and R-AMSTAR to 16 systematic reviews (eight Cochrane reviews and eight non-Cochrane reviews) from the field of occupational health...
July 11, 2017: BMC Medical Research Methodology
https://www.readbyqxmd.com/read/28693435/data-cleaning-and-management-protocols-for-linked-perinatal-research-data-a-good-practice-example-from-the-smoking-mums-maternal-use-of-medications-and-safety-study
#18
Duong Thuy Tran, Alys Havard, Louisa R Jorm
BACKGROUND: Data cleaning is an important quality assurance in data linkage research studies. This paper presents the data cleaning and preparation process for a large-scale cross-jurisdictional Australian study (the Smoking MUMS Study) to evaluate the utilisation and safety of smoking cessation pharmacotherapies during pregnancy. METHODS: Perinatal records for all deliveries (2003-2012) in the States of New South Wales (NSW) and Western Australia were linked to State-based data collections including hospital separation, emergency department and death data (mothers and babies) and congenital defect notifications (babies in NSW) by State-based data linkage units...
July 11, 2017: BMC Medical Research Methodology
https://www.readbyqxmd.com/read/28693507/estimating-parameters-for-probabilistic-linkage-of-privacy-preserved-datasets
#19
Adrian P Brown, Sean M Randall, Anna M Ferrante, James B Semmens, James H Boyd
BACKGROUND: Probabilistic record linkage is a process used to bring together person-based records from within the same dataset (de-duplication) or from disparate datasets using pairwise comparisons and matching probabilities. The linkage strategy and associated match probabilities are often estimated through investigations into data quality and manual inspection. However, as privacy-preserved datasets comprise encrypted data, such methods are not possible. In this paper, we present a method for estimating the probabilities and threshold values for probabilistic privacy-preserved record linkage using Bloom filters...
July 10, 2017: BMC Medical Research Methodology
https://www.readbyqxmd.com/read/28693492/barriers-to-publishing-in-biomedical-journals-perceived-by-a-sample-of-french-researchers-results-of-the-diazepam-study
#20
Martin Duracinsky, Christophe Lalanne, Laurence Rous, Aichata Fofana Dara, Lesya Baudoin, Claire Pellet, Alexandre Descamps, Fabienne Péretz, Olivier Chassany
BACKGROUND: As publishing is essential but competitive for researchers, difficulties in writing and submitting medical articles to biomedical journals are disabling. The DIAzePAM (Difficultés des Auteurs à la Publication d'Articles Médicaux) survey aimed to assess the difficulties experienced by researchers in the AP-HP (Assistance Publique - Hôpitaux de Paris, i.e., Paris Hospitals Board, France), the largest public health institution in Europe, when preparing articles for biomedical journals...
July 10, 2017: BMC Medical Research Methodology
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