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    1644 results match your criteria BMC Medical Research Methodology [Journal]

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    Does different information disclosure on placebo control affect blinding and trial outcomes? A case study of participant information leaflets of randomized placebo-controlled trials of acupuncture.
    BMC Med Res Methodol 2018 Jan 18;18(1):13. Epub 2018 Jan 18.
    Acupuncture and Meridian Science Research Centre, College of Korean Medicine, Kyung Hee University, Seoul, 02447, South Korea.
    Background: While full disclosure of information on placebo control in participant information leaflets (PILs) in a clinical trial is ethically required during informed consent, there have been concerning voices such complete disclosures may increase unnecessary nocebo responses, breach double-blind designs, and/or affect direction of trial outcomes. Taking an example of acupuncture studies, we aimed to examine what participants are told about placebo controls in randomized, placebo-controlled trials, and how it may affect blinding and trial outcomes.

    Methods: Authors of published randomized, placebo-controlled trials of acupuncture were identified from PubMed search and invited to provide PILs for their trials. Read More

    Getting messier with TIDieR: embracing context and complexity in intervention reporting.
    BMC Med Res Methodol 2018 Jan 18;18(1):12. Epub 2018 Jan 18.
    NIHR CLAHRC Greater Manchester, Manchester, UK.
    Background: The Template for Intervention Description and Replication (TIDieR) checklist and guide was developed by an international team of experts to promote full and accurate description of trial interventions. It is now widely used in health research. The aim of this paper is to describe the experience of using TIDieR outside of trials, in a range of applied health research contexts, and make recommendations on its usefulness in such settings. Read More

    Development and validation of self-reported line drawings of the modified Beighton score for the assessment of generalised joint hypermobility.
    BMC Med Res Methodol 2018 Jan 17;18(1):11. Epub 2018 Jan 17.
    Division of Rheumatology, Orthopaedics and Dermatology, School of Medicine, University of Nottingham, Nottingham, England.
    Background: The impracticalities and comparative expense of carrying out a clinical assessment is an obstacle in many large epidemiological studies. The purpose of this study was to develop and validate a series of electronic self-reported line drawing instruments based on the modified Beighton scoring system for the assessment of self-reported generalised joint hypermobility.

    Methods: Five sets of line drawings were created to depict the 9-point Beighton score criteria. Read More

    Reporting of heterogeneity of treatment effect in cohort studies: a review of the literature.
    BMC Med Res Methodol 2018 Jan 12;18(1):10. Epub 2018 Jan 12.
    INSERM U1153, ECAMO, METHODS, 27 rue du faubourg Saint-Jacques, Université Paris-Descartes, 75014, Paris 5, France.
    Background: This article corresponds to a literature review and analyze how heterogeneity of treatment (HTE) is reported and addressed in cohort studies and to evaluate the use of the different measures to HTE analysis.

    Methods: prospective cohort studies, in English language, measuring the effect of a treatment (pharmacological, interventional, or other) published among 119 core clinical journals (defined by the National Library of Medicine) in the last 16 years were selected in the following data source: Medline. One reviewer randomly sampled journal articles with 1: 1 stratification by journal type: high impact journals (the New England Journal of Medicine, JAMA, LANCET, Annals of Internal Medicine, BMJ and Plos Medicine) and low impact journal (the remaining journals) to identify 150 eligible studies. Read More

    A systematic review of comparisons between protocols or registrations and full reports in primary biomedical research.
    BMC Med Res Methodol 2018 Jan 11;18(1). Epub 2018 Jan 11.
    Department of Health Research Methods, Evidence, and Impact, McMaster University, St. Joseph's Healthcare, Hamilton, 501-25 Charlton Avenue East, Hamilton, ON, L8N 1Y2, Canada.
    Background: Prospective study protocols and registrations can play a significant role in reducing incomplete or selective reporting of primary biomedical research, because they are pre-specified blueprints which are available for the evaluation of, and comparison with, full reports. However, inconsistencies between protocols or registrations and full reports have been frequently documented. In this systematic review, which forms part of our series on the state of reporting of primary biomedical, we aimed to survey the existing evidence of inconsistencies between protocols or registrations (i. Read More

    A multiple imputation method based on weighted quantile regression models for longitudinal censored biomarker data with missing values at early visits.
    BMC Med Res Methodol 2018 Jan 11;18(1). Epub 2018 Jan 11.
    Division of Rheumatology, Department of Internal Medicine, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, Texas, USA.
    Background: In patient-based studies, biomarker data are often subject to left censoring due to the detection limits, or to incomplete sample or data collection. In the context of longitudinal regression analysis, inappropriate handling of these issues could lead to biased parameter estimates. We developed a specific multiple imputation (MI) strategy based on weighted censored quantile regression (CQR) that not only accounts for censoring, but also missing data at early visits when longitudinal biomarker data are modeled as a covariate. Read More

    Comparison of nuisance parameters in pediatric versus adult randomized trials: a meta-epidemiologic empirical evaluation.
    BMC Med Res Methodol 2018 Jan 10;18(1). Epub 2018 Jan 10.
    Pediatric Clinical Research Office, Emma Children's Hospital, Academic Medical Centre, Amsterdam, Netherlands.
    Background: We wished to compare the nuisance parameters of pediatric vs. adult randomized-trials (RCTs) and determine if the latter can be used in sample size computations of the former.

    Methods: In this meta-epidemiologic empirical evaluation we examined meta-analyses from the Cochrane Database of Systematic-Reviews, with at least one pediatric-RCT and at least one adult-RCT. Read More

    What kind of systematic review should I conduct? A proposed typology and guidance for systematic reviewers in the medical and health sciences.
    BMC Med Res Methodol 2018 Jan 10;18(1). Epub 2018 Jan 10.
    The Joanna Briggs Institute, The University of Adelaide, 55 King William Road, North Adelaide, Soueth Australia, 5005, Australia.
    Background: Systematic reviews have been considered as the pillar on which evidence-based healthcare rests. Systematic review methodology has evolved and been modified over the years to accommodate the range of questions that may arise in the health and medical sciences. This paper explores a concept still rarely considered by novice authors and in the literature: determining the type of systematic review to undertake based on a research question or priority. Read More

    Structure formats of randomised controlled trial abstracts: a cross-sectional analysis of their current usage and association with methodology reporting.
    BMC Med Res Methodol 2018 Jan 10;18(1). Epub 2018 Jan 10.
    Cochrane Oral Health, Division of Dentistry, School of Medical Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester Academic Health Science Centre, Oxford Road, Manchester, M13 9PL, UK.
    Background: The reporting of randomised controlled trial (RCT) abstracts is of vital importance. The primary objective of this study was to investigate the association between structure format and RCT abstracts' quality of methodology reporting, informed by the current requirement and usage of structure formats by leading general medical/internal medicine journals (secondary objective).

    Methods: A two-part cross-sectional study. Read More

    A comparison of estimators from self-controlled case series, case-crossover design, and sequence symmetry analysis for pharmacoepidemiological studies.
    BMC Med Res Methodol 2018 Jan 8;18(1). Epub 2018 Jan 8.
    Department of Biostatistics, School of Public Health, Graduate School of Medicine, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, Japan.
    Background: Despite the frequent use of self-controlled methods in pharmacoepidemiological studies, the factors that may bias the estimates from these methods have not been adequately compared in real-world settings. Here, we comparatively examined the impact of a time-varying confounder and its interactions with time-invariant confounders, time trends in exposures and events, restrictions, and misspecification of risk period durations on the estimators from three self-controlled methods. This study analyzed self-controlled case series (SCCS), case-crossover (CCO) design, and sequence symmetry analysis (SSA) using simulated and actual electronic medical records datasets. Read More

    Effects of pre-notification, invitation length, questionnaire length and reminder on participation rate: a quasi-randomised controlled trial.
    BMC Med Res Methodol 2018 Jan 5;18(1). Epub 2018 Jan 5.
    Department of Oncology-Pathology, Karolinska Institutet. Karolinska University Hospital, Z1:00, 171 76, Stockholm, Sweden.
    Background: Improving participation rates in epidemiologic studies using questionnaires and biological sampling is important for the generalizability of the outcome. The aim of this study was to examine the effects of pre-notification, invitation length, questionnaire length, and reminder on participation rate and to investigate whether some factors contributed to participants doing both the questionnaire and blood sampling as oppose to only one part.

    Methods: Our study was embedded within the pilot testing of a large population-based study about prostate cancer screening. Read More

    Evaluating screening approaches for hepatocellular carcinoma in a cohort of HCV related cirrhosis patients from the Veteran's Affairs Health Care System.
    BMC Med Res Methodol 2018 Jan 4;18(1). Epub 2018 Jan 4.
    Baylor College of Medicine, Houston, USA.
    Background: Hepatocellular carcinoma (HCC) has limited treatment options in patients with advanced stage disease and early detection of HCC through surveillance programs is a key component towards reducing mortality. The current practice guidelines recommend that high-risk cirrhosis patients are screened every six months with ultrasonography but these are done in local hospitals with variable quality leading to disagreement about the benefit of HCC surveillance. The well-established diagnostic biomarker α-Fetoprotein (AFP) is used widely in screening but the reported performance varies widely across studies. Read More

    A systematic comparison of recurrent event models for application to composite endpoints.
    BMC Med Res Methodol 2018 Jan 4;18(1). Epub 2018 Jan 4.
    Institute of Medical Biometry and Informatics, Universtiy Medical Center Ruprecht-Karls Universtiy Heidelberg, Im Neuenheimer Feld 130.3, Heidelberg, 69120, Germany.
    Background: Many clinical trials focus on the comparison of the treatment effect between two or more groups concerning a rarely occurring event. In this situation, showing a relevant effect with an acceptable power requires the observation of a large number of patients over a long period of time. For feasibility issues, it is therefore often considered to include several event types of interest, non-fatal or fatal, and to combine them within a composite endpoint. Read More

    A scoping review of comparisons between abstracts and full reports in primary biomedical research.
    BMC Med Res Methodol 2017 12 29;17(1):181. Epub 2017 Dec 29.
    Department of Health Research Methods, Evidence, and Impact, McMaster University, Hamilton, ON, Canada.
    Background: Evidence shows that research abstracts are commonly inconsistent with their corresponding full reports, and may mislead readers. In this scoping review, which is part of our series on the state of reporting of primary biomedical research, we summarized the evidence from systematic reviews and surveys, to investigate the current state of inconsistent abstract reporting, and to evaluate factors associated with improved reporting by comparing abstracts and their full reports.

    Methods: We searched EMBASE, Web of Science, MEDLINE, and CINAHL from January 1st 1996 to September 30th 2016 to retrieve eligible systematic reviews and surveys. Read More

    Abstract analysis method facilitates filtering low-methodological quality and high-bias risk systematic reviews on psoriasis interventions.
    BMC Med Res Methodol 2017 12 29;17(1):180. Epub 2017 Dec 29.
    IMIBIC/Reina Sofía University Hospital/UNiversity of Córdoba, Menendez Pidal Ave, Córdoba, 14005, Spain.
    Background: Article summaries' information and structure may influence researchers/clinicians' decisions to conduct deeper full-text analyses. Specifically, abstracts of systematic reviews (SRs) and meta-analyses (MA) should provide structured summaries for quick assessment. This study explored a method for determining the methodological quality and bias risk of full-text reviews using abstract information alone. Read More

    Can statistic adjustment of OR minimize the potential confounding bias for meta-analysis of case-control study? A secondary data analysis.
    BMC Med Res Methodol 2017 12 29;17(1):179. Epub 2017 Dec 29.
    Department of Epidemiology and Biostatistics, School of Public Health, Capital Medical University, Beijing, China.
    Background: Different confounder adjustment strategies were used to estimate odds ratios (ORs) in case-control study, i.e. how many confounders original studies adjusted and what the variables are. Read More

    The alarming problems of confounding equivalence using logistic regression models in the perspective of causal diagrams.
    BMC Med Res Methodol 2017 12 28;17(1):177. Epub 2017 Dec 28.
    Department of Biostatistics, School of Public Health, Shandong University, Jinan, People's Republic of China.
    Background: Confounders can produce spurious associations between exposure and outcome in observational studies. For majority of epidemiologists, adjusting for confounders using logistic regression model is their habitual method, though it has some problems in accuracy and precision. It is, therefore, important to highlight the problems of logistic regression and search the alternative method. Read More

    Compliance of systematic reviews in ophthalmology with the PRISMA statement.
    BMC Med Res Methodol 2017 12 28;17(1):178. Epub 2017 Dec 28.
    Guy's and St. Thomas' NHS Foundation Trust and Balliol College, University of Oxford, Oxford, UK.
    Background: Systematic reviews and meta-analyses are becoming increasingly important methods to summarize published research. Studies of ophthalmology may present additional challenges because of their potentially complex study designs. The aim of this study was to evaluate the reporting quality of systematic reviews and meta-analyses on topics in ophthalmology to determine compliance with the PRISMA guidelines. Read More

    A survey of prevalence of narrative and systematic reviews in five major medical journals.
    BMC Med Res Methodol 2017 12 28;17(1):176. Epub 2017 Dec 28.
    Melbourne School of Health Sciences, Department of Nursing, Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Melbourne, Australia.
    Background: Systematic reviews may provide less biased evidence than narrative reviews because they observe a strict methodology, similarly to primary studies. Hence, for clinical research questions, systematic reviews should be the study design of choice. It would be important to evaluate the prevalence and characteristics of narrative and systematic reviews published in prominent medical journals. Read More

    Development of an intervention to reduce antibiotic use for childhood coughs in UK primary care using critical synthesis of multi-method research.
    BMC Med Res Methodol 2017 12 28;17(1):175. Epub 2017 Dec 28.
    Centre for Academic Primary Care, Population Health Sciences, Bristol Medical School, University of Bristol, Bristol, UK.
    Background: Overuse of antibiotics contributes to the global threat of antimicrobial resistance. Antibiotic stewardship interventions address this threat by reducing the use of antibiotics in occasions or doses unlikely to be effective. We aimed to develop an evidence-based, theory-informed, intervention to reduce antibiotic prescriptions in primary care for childhood respiratory tract infections (RTI). Read More

    What's the uptake? Pragmatic RCTs may be used to estimate uptake, and thereby population impact of interventions, but better reporting of trial recruitment processes is needed.
    BMC Med Res Methodol 2017 12 22;17(1):174. Epub 2017 Dec 22.
    Centre for Research in Evidence Based Practice (CREBP), Bond University, Gold coast, QLD, 4229, Australia.
    Background: Effectiveness of interventions in pragmatic trials may not translate directly into population impact, because of limited uptake by clinicians and/or the public. Uptake of an intervention is influenced by a number of factors.

    Methods: We propose a method for calculating population impact of clinical interventions that accounts for the intervention uptake. Read More

    The development of CHAMP: a checklist for the appraisal of moderators and predictors.
    BMC Med Res Methodol 2017 12 21;17(1):173. Epub 2017 Dec 21.
    Institute for Health Sciences, Radboud university medical center, Nijmegen, The Netherlands.
    Background: Personalized healthcare relies on the identification of factors explaining why individuals respond differently to the same intervention. Analyses identifying such factors, so called predictors and moderators, have their own set of assumptions and limitations which, when violated, can result in misleading claims, and incorrect actions. The aim of this study was to develop a checklist for critically appraising the results of predictor and moderator analyses by combining recommendations from published guidelines and experts in the field. Read More

    Multiple Score Comparison: a network meta-analysis approach to comparison and external validation of prognostic scores.
    BMC Med Res Methodol 2017 12 21;17(1):172. Epub 2017 Dec 21.
    Epidemiology, Biostatistics and Prevention Institute, University of Zurich, Zurich, Switzerland.
    Background: Prediction models and prognostic scores have been increasingly popular in both clinical practice and clinical research settings, for example to aid in risk-based decision making or control for confounding. In many medical fields, a large number of prognostic scores are available, but practitioners may find it difficult to choose between them due to lack of external validation as well as lack of comparisons between them.

    Methods: Borrowing methodology from network meta-analysis, we describe an approach to Multiple Score Comparison meta-analysis (MSC) which permits concurrent external validation and comparisons of prognostic scores using individual patient data (IPD) arising from a large-scale international collaboration. Read More

    Tweedie distributions for fitting semicontinuous health care utilization cost data.
    BMC Med Res Methodol 2017 Dec 19;17(1):171. Epub 2017 Dec 19.
    Institute of Health Economics and Health Care Management, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Neuherberg, Germany.
    Background: The statistical analysis of health care cost data is often problematic because these data are usually non-negative, right-skewed and have excess zeros for non-users. This prevents the use of linear models based on the Gaussian or Gamma distribution. A common way to counter this is the use of Two-part or Tobit models, which makes interpretation of the results more difficult. Read More

    Accounting for parameter uncertainty in the definition of parametric distributions used to describe individual patient variation in health economic models.
    BMC Med Res Methodol 2017 Dec 15;17(1):170. Epub 2017 Dec 15.
    Health Technology and Services Research Department, MIRA institute for Biomedical Technology and Technical Medicine, University of Twente, P.O. Box 217, 7500 AE, Enschede, The Netherlands.
    Background: Parametric distributions based on individual patient data can be used to represent both stochastic and parameter uncertainty. Although general guidance is available on how parameter uncertainty should be accounted for in probabilistic sensitivity analysis, there is no comprehensive guidance on reflecting parameter uncertainty in the (correlated) parameters of distributions used to represent stochastic uncertainty in patient-level models. This study aims to provide this guidance by proposing appropriate methods and illustrating the impact of this uncertainty on modeling outcomes. Read More

    User testing of an adaptation of fishbone diagrams to depict results of systematic reviews.
    BMC Med Res Methodol 2017 Dec 12;17(1):169. Epub 2017 Dec 12.
    RTI International, 3040 East Cornwallis Rd, Research Triangle Park, Durham, NC, 27709, USA.
    Background: Summary of findings tables in systematic reviews are highly informative but require epidemiological training to be interpreted correctly. The usage of fishbone diagrams as graphical displays could offer researchers an effective approach to simplify content for readers with limited epidemiological training. In this paper we demonstrate how fishbone diagrams can be applied to systematic reviews and present the results of an initial user testing. Read More

    Accounting for misclassification bias of binary outcomes due to underscreening: a sensitivity analysis.
    BMC Med Res Methodol 2017 Dec 12;17(1):168. Epub 2017 Dec 12.
    Division of Biostatistics and Epidemiology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave, MLC 5041, Cincinnati, OH, 45229, USA.
    Background: Diagnostic tests are performed in a subset of the population who are at higher risk, resulting in undiagnosed cases among those who do not receive the test. This poses a challenge for estimating the prevalence of the disease in the study population, and also for studying the risk factors for the disease.

    Methods: We formulate this problem as a missing data problem because the disease status is unknown for those who do not receive the test. Read More

    Learning from older peoples' reasons for participating in demanding, intensive epidemiological studies: a qualitative study.
    BMC Med Res Methodol 2017 Dec 12;17(1):167. Epub 2017 Dec 12.
    Academic Geriatric Medicine, University of Southampton, Southampton, UK.
    Background: Recruitment rates of older people in epidemiological studies, although relatively higher than in clinical trials, have declined in recent years. This study aimed to explore motivating factors and concerns among older participants in an intensive epidemiological study (Hertfordshire Sarcopenia Study - HSS) and identify those that could aid future recruitment to epidemiological studies and clinical trials.

    Methods: Participants of the HSS fasted overnight and travelled several hours each way to the research facility at an English hospital for extensive diet/lifestyle questionnaires and investigations to assess muscle including blood tests and a muscle biopsy. Read More

    Methods to perform systematic reviews of patient preferences: a literature survey.
    BMC Med Res Methodol 2017 Dec 11;17(1):166. Epub 2017 Dec 11.
    Department of Public Health, China Medical University, No 91 Hsueh-Shih Road, Taichung, Taiwan.
    Background: Systematic reviews are a commonly used research design in the medical field to synthesize study findings. At present-although several systematic reviews of patient preference studies are published-there is no clear guidance available for researchers to conduct this type of systematic review. The aim of our study was to learn the most current practice of conducting these systematic reviews by conducting a survey of the literature regarding reviews of quantitative patient preference studies. Read More

    On the use of the outcome variable "small for gestational age" when gestational age is a potential mediator: a maternal asthma perspective.
    BMC Med Res Methodol 2017 Dec 11;17(1):165. Epub 2017 Dec 11.
    Department of Mathematics, Université du Québec à Montréal, C.P. 8888, Succursale Centre-ville, Montréal, Québec, H3C 3P8, Canada.
    Background: The variable "small for gestational age," frequently defined as birth weight below the 10th percentile in a gestational age and sex-normalized population, is nowadays generally perceived as a more adequate measure than birth weight or low birth weight (birth weight < 2500 g) to capture fetal growth. However, the use of small for gestational age rather than birth weight or low birth weight as an outcome (dependent) variable may have important impacts on the interpretation of analyses aimed at estimating the causal effect of an exposure of interest on infants. We hypothesized potential differences in both types of effects estimated (direct or total) and in ability to control for confounding bias. Read More

    Longitudinal drop-out and weighting against its bias.
    BMC Med Res Methodol 2017 Dec 8;17(1):164. Epub 2017 Dec 8.
    Institute of Sport and Sport Science, Karlsruhe Institute of Technology, 76131, Karlsruhe, Germany.
    Background: The bias caused by drop-out is an important factor in large population-based epidemiological studies. Many studies account for it by weighting their longitudinal data, but to date there is no detailed final approach for how to conduct these weights.

    Methods: In this study we describe the observed longitudinal bias and a three-step longitudinal weighting approach used for the longitudinal data in the MoMo baseline (N = 4528, 4-17 years) and wave 1 study with 2807 (62%) participants between 2003 and 2012. Read More

    Validity of mobile electronic data capture in clinical studies: a pilot study in a pediatric population.
    BMC Med Res Methodol 2017 Dec 8;17(1):163. Epub 2017 Dec 8.
    Clinical Trial Unit, Department of Clinical Research, University and University Hospital of Basel, Schanzenstrasse 55, 4031, Basel, Switzerland.
    Background: Clinical studies in children are necessary yet conducting multiple visits at study centers remains challenging. The success of "care-at-home" initiatives and remote clinical trials suggests their potential to facilitate conduct of pediatric studies. This pilot aimed to study the feasibility of remotely collecting valid (i. Read More

    When and how should multiple imputation be used for handling missing data in randomised clinical trials - a practical guide with flowcharts.
    BMC Med Res Methodol 2017 Dec 6;17(1):162. Epub 2017 Dec 6.
    The Copenhagen Trial Unit, Centre for Clinical Intervention Research, Rigshospitalet, Copenhagen University Hospital, Copenhagen, Denmark.
    Background: Missing data may seriously compromise inferences from randomised clinical trials, especially if missing data are not handled appropriately. The potential bias due to missing data depends on the mechanism causing the data to be missing, and the analytical methods applied to amend the missingness. Therefore, the analysis of trial data with missing values requires careful planning and attention. Read More

    Classification schemes for knowledge translation interventions: a practical resource for researchers.
    BMC Med Res Methodol 2017 Dec 6;17(1):161. Epub 2017 Dec 6.
    University of Alberta, Edmonton, Canada.
    Background: As implementation science advances, the number of interventions to promote the translation of evidence into healthcare, health systems, or health policy is growing. Accordingly, classification schemes for these knowledge translation (KT) interventions have emerged. A recent scoping review identified 51 classification schemes of KT interventions to integrate evidence into healthcare practice; however, the review did not evaluate the quality of the classification schemes or provide detailed information to assist researchers in selecting a scheme for their context and purpose. Read More

    ERDO - a framework to select an appropriate randomization procedure for clinical trials.
    BMC Med Res Methodol 2017 Dec 4;17(1):159. Epub 2017 Dec 4.
    Department of Medical Statistics, RWTH Aachen University Aachen, Pauwelsstrasse 19, Aachen, Germany.
    Background: Randomization is considered to be a key feature to protect against bias in randomized clinical trials. Randomization induces comparability with respect to known and unknown covariates, mitigates selection bias, and provides a basis for inference. Although various randomization procedures have been proposed, no single procedure performs uniformly best. Read More

    Performance of the marginal structural cox model for estimating individual and joined effects of treatments given in combination.
    BMC Med Res Methodol 2017 Dec 4;17(1):160. Epub 2017 Dec 4.
    Sorbonne Universités, INSERM, UPMC Université Paris 06, Institut Pierre Louis d'épidémiologie et de Santé Publique (IPLESP UMRS 1136), Paris, France.
    Background: The Marginal Structural Cox Model (Cox-MSM), an alternative approach to handle time-dependent confounder, was introduced for survival analysis and applied to estimate the joint causal effect of two time-dependent nonrandomized treatments on survival among HIV-positive subjects. Nevertheless, Cox-MSM performance in the case of multiple treatments has not been fully explored under different degree of time-dependent confounding for treatments or in case of interaction between treatments. We aimed to evaluate and compare the performance of the marginal structural Cox model (Cox-MSM) to the standard Cox model in estimating the treatment effect in the case of multiple treatments under different scenarios of time-dependent confounding and when an interaction between treatment effects is present. Read More

    Sample size calculations based on a difference in medians for positively skewed outcomes in health care studies.
    BMC Med Res Methodol 2017 Dec 2;17(1):157. Epub 2017 Dec 2.
    Department of Statistical Science, University College London, Gower St., London, WC1E 6BT, UK.
    Background: In healthcare research, outcomes with skewed probability distributions are common. Sample size calculations for such outcomes are typically based on estimates on a transformed scale (e.g. Read More

    What does it mean when people say that they have received expressions of concern about their drinking or advice to cut down on the AUDIT scale?
    BMC Med Res Methodol 2017 Dec 2;17(1):158. Epub 2017 Dec 2.
    Alcohol Treatment Center, Department of Community Medicine and Health, Lausanne University Hospital, Lausanne, Vaud, Switzerland.
    Background: The Alcohol Use Disorders Identification Test (AUDIT) is a commonly used scale to measure severity of alcohol consumption that contains an item asking if anyone has expressed concern about your drinking or suggested you cut down. What does it mean when a participant says yes to this question?

    Methods: Participants who were 18 or older and who drank at least weekly were recruited to complete a survey about their drinking from the Mechanical Turk platform. Comparisons were made between at risk (n = 2565) and high risk drinkers (n = 581) who said that someone had expressed concern about their drinking regarding who had expressed concern. Read More

    Performance comparison of first-order conditional estimation with interaction and Bayesian estimation methods for estimating the population parameters and its distribution from data sets with a low number of subjects.
    BMC Med Res Methodol 2017 Dec 1;17(1):154. Epub 2017 Dec 1.
    College of Pharmacy, Chungnam National University, Daejeon, 34134, Republic of Korea.
    Background: Exploratory preclinical, as well as clinical trials, may involve a small number of patients, making it difficult to calculate and analyze the pharmacokinetic (PK) parameters, especially if the PK parameters show very high inter-individual variability (IIV). In this study, the performance of a classical first-order conditional estimation with interaction (FOCE-I) and expectation maximization (EM)-based Markov chain Monte Carlo Bayesian (BAYES) estimation methods were compared for estimating the population parameters and its distribution from data sets having a low number of subjects.

    Methods: In this study, 100 data sets were simulated with eight sampling points for each subject and with six different levels of IIV (5%, 10%, 20%, 30%, 50%, and 80%) in their PK parameter distribution. Read More

    Mobile electronic versus paper case report forms in clinical trials: a randomized controlled trial.
    BMC Med Res Methodol 2017 Dec 1;17(1):153. Epub 2017 Dec 1.
    Clinical Research Unit, Charité Campus Mitte, Berlin Institute of Health (BIH), Charitéplatz 1, 10117, Berlin, Germany.
    Background: Regulations, study design complexity and amounts of collected and shared data in clinical trials render efficient data handling procedures inevitable. Recent research suggests that electronic data capture can be key in this context but evidence is insufficient. This randomized controlled parallel group study tested the hypothesis that time efficiency is superior when electronic (eCRF) instead of paper case report forms (pCRF) are used for data collection. Read More

    New methods for estimating follow-up rates in cohort studies.
    BMC Med Res Methodol 2017 Dec 1;17(1):155. Epub 2017 Dec 1.
    Department of Epidemiology & Population Health, Albert Einstein College of Medicine, Bronx, NY, 10461, USA.
    Background: The follow-up rate, a standard index of the completeness of follow-up, is important for assessing the validity of a cohort study. A common method for estimating the follow-up rate, the "Percentage Method", defined as the fraction of all enrollees who developed the event of interest or had complete follow-up, can severely underestimate the degree of follow-up. Alternatively, the median follow-up time does not indicate the completeness of follow-up, and the reverse Kaplan-Meier based method and Clark's Completeness Index (CCI) also have limitations. Read More

    Using Mechanical Turk to recruit participants for internet intervention research: experience from recruitment for four trials targeting hazardous alcohol consumption.
    BMC Med Res Methodol 2017 Dec 1;17(1):156. Epub 2017 Dec 1.
    Centre for Addiction and Mental Health, 33 Russell St., Toronto, Ontario, M5S 2S1, Canada.
    Background: Mechanical Turk (MTurk) is an online portal operated by Amazon where 'requesters' (individuals or businesses) can submit jobs for 'workers.' MTurk is used extensively by academics as a quick and cheap means of collecting questionnaire data, including information on alcohol consumption, from a diverse sample of participants. We tested the feasibility of recruiting for alcohol Internet intervention trials through MTurk. Read More

    Frequency of data extraction errors and methods to increase data extraction quality: a methodological review.
    BMC Med Res Methodol 2017 Nov 28;17(1):152. Epub 2017 Nov 28.
    Institute for Research in Operative Medicinem, Chair of Surgical Research, Faculty of Health, School of Medicine, Witten/Herdecke University, Ostmerheimer Str. 200, 51109, Cologne, Germany.
    Background: Our objective was to assess the frequency of data extraction errors and its potential impact on results in systematic reviews. Furthermore, we evaluated the effect of different extraction methods, reviewer characteristics and reviewer training on error rates and results.

    Methods: We performed a systematic review of methodological literature in PubMed, Cochrane methodological registry, and by manual searches (12/2016). Read More

    Is the information of systematic reviews published in nursing journals up-to-date? a cross-sectional study.
    BMC Med Res Methodol 2017 Nov 25;17(1):151. Epub 2017 Nov 25.
    Alice Lee Centre for Nursing Studies, Yong Loo Lin School of Medicine, Level 2, Clinical Research Centre, Block MD11, 10 Medical Drive, Singapore, 117597, Singapore.
    Background: An up-to-date systematic review is important for researchers to decide whether to embark on new research or continue supporting ongoing studies. The aim of this study is to examine the time taken between the last search, submission, acceptance and publication dates of systematic reviews published in nursing journals.

    Methods: Nursing journals indexed in Journal Citation Reports were first identified. Read More

    Recruiting former melanoma patients via hospitals in comparison to office-based dermatologists in a register-based cohort study that required indirect contact.
    BMC Med Res Methodol 2017 Nov 22;17(1):150. Epub 2017 Nov 22.
    Institute of Medical Biostatistics, Epidemiology and Informatics (IMBEI), University Medical Center of the Johannes Gutenberg-University Mainz, Mainz, Germany.
    Background: There are detailed reviews about different recruitment strategies, but not with regard to differences between recruitment of hospital-based versus office-based physicians. Within this study, the two different recruitment schemes are compared. Advantages and disadvantages of different ways of recruitment in registry-based studies are discussed. Read More

    Design considerations and analysis planning of a phase 2a proof of concept study in rheumatoid arthritis in the presence of possible non-monotonicity.
    BMC Med Res Methodol 2017 Oct 2;17(1):149. Epub 2017 Oct 2.
    Medical Statistics Group, University of Sheffield, Sheffield, UK.
    Background: It is important to quantify the dose response for a drug in phase 2a clinical trials so the optimal doses can then be selected for subsequent late phase trials. In a phase 2a clinical trial of new lead drug being developed for the treatment of rheumatoid arthritis (RA), a U-shaped dose response curve was observed. In the light of this result further research was undertaken to design an efficient phase 2a proof of concept (PoC) trial for a follow-on compound using the lessons learnt from the lead compound. Read More

    Item response models for the longitudinal analysis of health-related quality of life in cancer clinical trials.
    BMC Med Res Methodol 2017 Sep 26;17(1):148. Epub 2017 Sep 26.
    Biometrics Unit, Institut du Cancer Montpellier, 208 Avenue des Apothicaires, Montpellier, 34298, France.
    Background: The use of health-related quality of life (HRQoL) as an endpoint in cancer clinical trials is growing rapidly. Hence, research into the statistical approaches used to analyze HRQoL data is of major importance, and could lead to a better understanding of the impact of treatments on the everyday life and care of patients. Amongst the models that are used for the longitudinal analysis of HRQoL, we focused on the mixed models from item response theory, to directly analyze raw data from questionnaires. Read More

    Predicting the multi-domain progression of Parkinson's disease: a Bayesian multivariate generalized linear mixed-effect model.
    BMC Med Res Methodol 2017 Sep 25;17(1):147. Epub 2017 Sep 25.
    Department of Neurology, Pennsylvania State University Hershey Medical Center, Hershey, PA, 17033, USA.
    Background: It is challenging for current statistical models to predict clinical progression of Parkinson's disease (PD) because of the involvement of multi-domains and longitudinal data.

    Methods: Past univariate longitudinal or multivariate analyses from cross-sectional trials have limited power to predict individual outcomes or a single moment. The multivariate generalized linear mixed-effect model (GLMM) under the Bayesian framework was proposed to study multi-domain longitudinal outcomes obtained at baseline, 18-, and 36-month. Read More

    Systematic review of statistical approaches to quantify, or correct for, measurement error in a continuous exposure in nutritional epidemiology.
    BMC Med Res Methodol 2017 Sep 19;17(1):146. Epub 2017 Sep 19.
    Population Health & Occupational Disease, National Heart and Lung Institute, Imperial College London, London, UK.
    Background: Several statistical approaches have been proposed to assess and correct for exposure measurement error. We aimed to provide a critical overview of the most common approaches used in nutritional epidemiology.

    Methods: MEDLINE, EMBASE, BIOSIS and CINAHL were searched for reports published in English up to May 2016 in order to ascertain studies that described methods aimed to quantify and/or correct for measurement error for a continuous exposure in nutritional epidemiology using a calibration study. Read More

    Pragmatic clinical trials embedded in healthcare systems: generalizable lessons from the NIH Collaboratory.
    BMC Med Res Methodol 2017 Sep 18;17(1):144. Epub 2017 Sep 18.
    Duke Clinical Research Institute, 2400 Pratt St., Durham, NC, 27710, USA.
    Background: The clinical research enterprise is not producing the evidence decision makers arguably need in a timely and cost effective manner; research currently involves the use of labor-intensive parallel systems that are separate from clinical care. The emergence of pragmatic clinical trials (PCTs) poses a possible solution: these large-scale trials are embedded within routine clinical care and often involve cluster randomization of hospitals, clinics, primary care providers, etc. Interventions can be implemented by health system personnel through usual communication channels and quality improvement infrastructure, and data collected as part of routine clinical care. Read More

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