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Sample size calculation

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https://www.readbyqxmd.com/read/28815876/a-treatment-development-study-of-a-cognitive-and-mindfulness-based-therapy-for-adolescents-with-co-occurring-post-traumatic-stress-and-substance-use-disorder
#1
Lisa R Fortuna, Michelle V Porche, Auralyd Padilla
OBJECTIVE: Substance use is common among adolescents with post-traumatic stress disorder (PTSD). We aimed to develop and study an integrated treatment for adolescents with co-occurring disorders. DESIGN: This is a therapy development and open pilot trial study of a manualized therapy for adolescents with post-traumatic stress, depression, and substance use that uses a combination of cognitive therapy (CT) and mindfulness. METHODS: Descriptive statistics and paired sample t-tests were calculated to assess for changes in PTSD symptoms, depression, and substance use frequency from baseline to end of treatment using standardized measures and validated by urine drug screens...
August 16, 2017: Psychology and Psychotherapy
https://www.readbyqxmd.com/read/28815655/a-clinical-trial-design-using-the-concept-of-proportional-time-using-the-generalized-gamma-ratio-distribution
#2
Milind A Phadnis, James B Wetmore, Matthew S Mayo
Traditional methods of sample size and power calculations in clinical trials with a time-to-event end point are based on the logrank test (and its variations), Cox proportional hazards (PH) assumption, or comparison of means of 2 exponential distributions. Of these, sample size calculation based on PH assumption is likely the most common and allows adjusting for the effect of one or more covariates. However, when designing a trial, there are situations when the assumption of PH may not be appropriate. Additionally, when it is known that there is a rapid decline in the survival curve for a control group, such as from previously conducted observational studies, a design based on the PH assumption may confer only a minor statistical improvement for the treatment group that is neither clinically nor practically meaningful...
August 16, 2017: Statistics in Medicine
https://www.readbyqxmd.com/read/28814156/a-method-to-compare-the-performance-of-two-molecular-diagnostic-tools-in-the-absence-of-a-gold-standard
#3
Xiaonan Xue, Maja Oktay, Sumanta Goswami, Mimi Y Kim
The paper is motivated by the problem of comparing the accuracy of two molecular tests in detecting genetic mutations in tumor samples when there is no gold standard test. Commonly used sequencing methods require a large number of tumor cells in the tumor sample and the proportion of tumor cells with mutation positivity to be above a threshold level whereas new tests aim to reduce the requirement for number of tumor cells and the threshold level. A new latent class model is proposed to compare these two tests in which a random variable is used to represent the unobserved proportion of mutation positivity so that these two tests are conditionally dependent; furthermore, an independent random variable is included to address measurement error associated with the reading from each test, while existing latent class models often assume conditional independence and do not allow measurement error...
January 1, 2017: Statistical Methods in Medical Research
https://www.readbyqxmd.com/read/28812160/robotic-versus-open-pancreatoduodenectomy-a-propensity-score-matched-analysis-based-on-factors-predictive-of-postoperative-pancreatic-fistula
#4
Niccolò Napoli, Emanuele F Kauffmann, Francesca Menonna, Francesca Costa, Sara Iacopi, Gabriella Amorese, Serena Giorgi, Angelo Baggiani, Ugo Boggi
BACKGROUND: Improvement in morbidity of pancreatoduodenectomy (PD) largely depends on the reduction in the incidence of clinically relevant (CR) postoperative pancreatic fistula (POPF). METHODS: After internal validation of the clinical risk score (CRS) of POPF, and identification of other predictive factors for POPF, robotic (RPD), and open (OPD) PDs were stratified into risk categories and matched by propensity scores. The primary endpoint of this study was incidence of CR-POPF...
August 15, 2017: Surgical Endoscopy
https://www.readbyqxmd.com/read/28811870/meat-inspection-of-reindeer-a-rich-source-of-data-for-monitoring-food-safety-and-animal-and-environmental-health-in-sweden
#5
Arja Helena Kautto, Ivar Vågsholm, Rauni Niskanen
Background: ​This study scrutinized carcass conditions recorded in post mortem inspections (PMI) of reindeer (Rangifer tarandus tarandus, L.) during 2015-2016 because of the importance for monitoring food safety and animal and environmental health threats. Material and methods: PMI results were retrieved from the National Food Agency. A negative binomial regression model was applied. For actual parameters, incident risk rate (IRR) with confidence intervals was calculated. Results and discussion: The number of conditions found in PMI varied widely between years and batches...
2017: Infection Ecology & Epidemiology
https://www.readbyqxmd.com/read/28810925/surgical-versus-percutaneous-isolated-pelvic-perfusion-ipp-for-advanced-melanoma-comparison-in-terms-of-melphalan-pharmacokinetic-pelvic-bio-availability
#6
Stefano Guadagni, Giancarlo Palumbo, Giammaria Fiorentini, Marco Clementi, Luca Marsili, Aldo Victor Giordano, Francesco Masedu, Marco Valenti
BACKGROUND: Isolated pelvic perfusion (IPP) can be used to treat unresectable melanoma metastases of the pelvis. IPP can be performed either by surgical or percutaneous approaches, using different balloon catheters. The aim of this study was to examine whether the surgical and percutaneous approaches were comparable with respect to tumor drug exposure in the pelvis. METHODS: A pharmacokinetic study was performed in 5 melanoma patients treated with surgical IPP and five with percutaneous IPP...
August 15, 2017: BMC Research Notes
https://www.readbyqxmd.com/read/28810895/understanding-the-cluster-randomised-crossover-design-a-graphical-illustraton-of-the-components-of-variation-and%C3%A2-a-sample-size%C3%A2-tutorial
#7
Sarah J Arnup, Joanne E McKenzie, Karla Hemming, David Pilcher, Andrew B Forbes
BACKGROUND: In a cluster randomised crossover (CRXO) design, a sequence of interventions is assigned to a group, or 'cluster' of individuals. Each cluster receives each intervention in a separate period of time, forming 'cluster-periods'. Sample size calculations for CRXO trials need to account for both the cluster randomisation and crossover aspects of the design. Formulae are available for the two-period, two-intervention, cross-sectional CRXO design, however implementation of these formulae is known to be suboptimal...
August 15, 2017: Trials
https://www.readbyqxmd.com/read/28810122/crystal-face-distributions-and-surface-site-densities-of-two-synthetic-goethites-implications-for-adsorption-capacities-as-a-function-of-particle-size
#8
Kenneth J T Livi, Mario Villalobos, Rowan K Leary, Maria Varela, Jon Barnard, Milton Villacís-García, Rodolfo Zanella, Anna Goodridge, Paul A Midgley
Two synthetic goethites of varying crystal sizes distributions were analyzed by BET, conventional TEM, cryo-TEM, atomic resolution STEM and HRTEM, and electron tomography in order to determine the effects of crystal size, shape, and atomic scale surface roughness on their adsorption capacities. The two samples were determined by BET to have very different site densities based on CrVI adsorption experiments. Model specific surfaces areas generated from TEM observations showed that, based on size and shape, there should be little difference in their adsorption capacities...
August 15, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28808432/grazing-incidence-small-angle-neutron-scattering-from-structures-below-an-interface
#9
Shirin Nouhi, Maja S Hellsing, Vassilios Kapaklis, Adrian R Rennie
Changes of scattering are observed as the grazing angle of incidence of an incoming beam increases and probes different depths in samples. A model has been developed to describe the observed intensity in grazing-incidence small-angle neutron scattering (GISANS) experiments. This includes the significant effects of instrument resolution, the sample transmission, which depends on both absorption and scattering, and the sample structure. The calculations are tested with self-organized structures of two colloidal samples with different size particles that were measured on two different instruments...
August 1, 2017: Journal of Applied Crystallography
https://www.readbyqxmd.com/read/28808265/study-of-dynamical-heterogeneities-in-colloidal-nanoclay-suspensions-approaching-dynamical-arrest
#10
Paramesh Gadige, Debasish Saha, Sanjay Kumar Behera, Ranjini Bandyopadhyay
The dynamics of aqueous Laponite clay suspensions slow down with increasing sample waiting time (t w ). This behavior, and the material fragility that results, closely resemble the dynamical slowdown in fragile supercooled liquids with decreasing temperature, and are typically ascribed to the increasing sizes of distinct dynamical heterogeneities in the sample. In this article, we characterize the dynamical heterogeneities in Laponite suspensions by invoking the three-point dynamic susceptibility formalism...
August 14, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28807846/the-reliability-of-commonly-used-electrophysiology-measures
#11
K E Brown, K R Lohse, I M S Mayer, G Strigaro, M Desikan, E P Casula, S Meunier, T Popa, J-C Lamy, O Odish, B R Leavitt, A Durr, R A C Roos, S J Tabrizi, J C Rothwell, L A Boyd, M Orth
BACKGROUND: Electrophysiological measures can help understand brain function both in healthy individuals and in the context of a disease. Given the amount of information that can be extracted from these measures and their frequent use, it is essential to know more about their inherent reliability. OBJECTIVE/HYPOTHESIS: To understand the reliability of electrophysiology measures in healthy individuals. We hypothesized that measures of threshold and latency would be the most reliable and least susceptible to methodological differences between study sites...
July 31, 2017: Brain Stimulation
https://www.readbyqxmd.com/read/28807251/how-to-conduct-a-high-quality-original-study-on-a-diagnostic-research-topic
#12
REVIEW
Xiaomei Yao, Emily Vella
As health research methodologists and journal reviewers, we noticed that the methodological rigor of many publications on diagnostic or prognostic topics in the medical literature could be improved. We present a concise and clear series of reviews to help clinicians and health researchers to master the basic key components of how to conduct a high-quality original study or systematic review on a diagnostic or prognostic research topic from a methodological perspective. This is the first review of the series, which focuses on how to conduct a high-quality diagnostic study...
September 2017: Surgical Oncology
https://www.readbyqxmd.com/read/28806767/hydrodynamic-repulsion-of-spheroidal-microparticles-from-micro-rough-surfaces
#13
Aleksey V Belyaev
Isolation of microparticles and biological cells from mixtures and suspensions is a central problem in a variety of biomedical applications. This problem, for instance, is of an immense importance for microfluidic devices manipulating with whole blood samples. It is instructive to know how the mobility and dynamics of rigid microparticles is altered by the presence of micrometer-size roughness on walls. The presented theoretical study addresses this issue via computer simulations. The approach is based on a combination of the Lattice Boltzmann method for calculating hydrodynamics and the Lagrangian Particle dynamics method to describe the dynamics of cell membranes...
2017: PloS One
https://www.readbyqxmd.com/read/28806144/particle-size-distributions-of-lead-measured-in-battery-manufacturing-and-secondary-smelter-facilities-and-implications-in-setting-workplace-lead-exposure-limits
#14
Catherine Petito Boyce, Sonja N Sax, Joel M Cohen
Inhalation plays an important role in exposures to lead in airborne particulate matter in occupational settings, and particle size determines where and how much of airborne lead is deposited in the respiratory tract and how much is subsequently absorbed into the body. Although some occupational airborne lead particle size data have been published, limited information is available reflecting current workplace conditions in the U.S. To address this data gap, the Battery Council International (BCI) conducted workplace monitoring studies at nine lead acid battery manufacturing facilities (BMFs) and five secondary smelter facilities (SSFs) across the U...
August 2017: Journal of Occupational and Environmental Hygiene
https://www.readbyqxmd.com/read/28805717/the-fragility-index-in-a-cohort-of-pediatric-randomized-controlled-trials
#15
Travis J Matics, Nadia Khan, Priti Jani, Jason M Kane
Data suggest inadequacy of common statistical techniques for reporting outcomes in clinical trials. The Fragility Index can measure how many events the statistical significance hinges on, and may facilitate better interpretation of trial results. This study aimed to assess the Fragility Index in pediatric randomized controlled trials (RCTs) with statistically significant findings published in high-quality medical journals. A Fragility Index was calculated on included trials with dichotomous positive outcomes...
August 14, 2017: Journal of Clinical Medicine
https://www.readbyqxmd.com/read/28803112/in-vivo-documentation-of-shape-and-position-changes-of-mri-visible-mesh-placed-in-rectovaginal-septum
#16
Urbankova Iva, Sindhwani Nikhil, Callewaert Geertje, Turri Alice, Rinkijevic Rita, Hympanova Lucie, Feola Andrew, Deprest Jan
BACKGROUND AND OBJECTIVE: Large deformations in synthetic meshes used in pelvic organ prolapse surgery may lead to suboptimal support for the underlying tissue, graft-related complications as well as recurrence. Our aim was to quantify in vivo longitudinal changes in mesh shape and geometry in a large animal model. We compare two commonly used mesh shapes, armed and flat, that are differently affixed. The secondary outcomes were active and passive biomechanical properties. METHODS: A total of 18 animals were used...
August 5, 2017: Journal of the Mechanical Behavior of Biomedical Materials
https://www.readbyqxmd.com/read/28802773/active-physiotherapy-interventions-following-total-knee-arthroplasty-in-the-hospital-and-inpatient-rehabilitation-settings-a-systematic-review-and-meta-analysis
#17
REVIEW
Kate G Henderson, Jason A Wallis, David A Snowdon
BACKGROUND: Physiotherapy is a routine component of postoperative management following total knee arthroplasty (TKA). As the demand for surgery increases it is vital that postoperative physiotherapy interventions are effective and efficient. OBJECTIVES: Determine the most beneficial active physiotherapy interventions in acute hospital and inpatient rehabilitation for improving pain, activity, range of motion and reducing length of stay for adults who have undergone TKA...
February 1, 2017: Physiotherapy
https://www.readbyqxmd.com/read/28802552/randomized-controlled-trial-comparing-radiologic-pigtail-retained-gastrostomy-and-radiologic-mushroom-retained-gastrostomy
#18
Kichang Han, Man-Deuk Kim, Joon Ho Kwon, Yong Seek Kim, Gyoung Min Kim, Junhyung Lee, Woosun Choi, Jong Yun Won, Do Yun Lee
PURPOSE: To prospectively compare 2 different types of percutaneous fluoroscopic gastrostomy procedures (pigtail-retained gastrostomy [PG] vs mushroom-retained gastrostomy [MG]). MATERIALS AND METHODS: Between March 2014 and February 2016, 100 patients were randomly assigned to receive 14-F PG or 20-F MG. Block randomization (block size 4) was performed, and sample size was calculated to assess the difference in minor complications. One patient withdrew from the study after allocation...
August 9, 2017: Journal of Vascular and Interventional Radiology: JVIR
https://www.readbyqxmd.com/read/28801563/the-global-burden-of-lower-urinary-tract-symptoms-suggestive-of-benign-prostatic-hyperplasia-a-systematic-review-and-meta-analysis
#19
Shaun Wen Huey Lee, Esther Mei Ching Chan, Yin Key Lai
Benign prostatic hyperplasia is a common non-malignant condition among older men, but the epidemiology is poorly characterised. We summarised and determined the global prevalence of benign prostatic hyperplasia. A systematic search on PubMed, EMBASE and CENTRAL was performed up until 31(st) July 2016. Studies that described the epidemiology of benign prostatic hyperplasia were included and cumulative plots of prevalence estimates were calculated. A total of 31 prevalence rate estimates from 25 countries were identified...
August 11, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28801438/associations-between-polypharmacy-and-treatment-intensity-for-hypertension-and-diabetes-a-cross-sectional-study-of-nursing-home-patients-in-british-columbia-canada
#20
Rita McCracken, James McCormack, Margaret J McGregor, Sabrina T Wong, Scott Garrison
OBJECTIVES: Describe nursing home polypharmacy prevalence in the context of prescribing for diabetes and hypertension and determine possible associations between lower surrogate markers for treated hypertension and diabetes (overtreatment) and polypharmacy. DESIGN: Cross-sectional study. SETTING: 6 nursing homes in British Columbia, Canada. PARTICIPANTS: 214 patients residing in one of the selected facilities during data collection period...
August 11, 2017: BMJ Open
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