Specifying the target difference in the primary outcome for a randomised controlled trial: guidance for researchers.

Background: Central to the design of a randomised controlled trial is the calculation of the number of participants needed. This is typically achieved by specifying a target difference and calculating the corresponding sample size, which provides reassurance that the trial will have the required statistical power (at the planned statistical significance level) to identify whether a difference of a particular magnitude exists. Beyond pure statistical or scientific concerns, it is ethically imperative that an appropriate number of participants should be recruited.

Methods for specifying the target difference in a randomised controlled trial: the Difference ELicitation in TriAls (DELTA) systematic review.

Background: Randomised controlled trials (RCTs) are widely accepted as the preferred study design for evaluating healthcare interventions. When the sample size is determined, a (target) difference is typically specified that the RCT is designed to detect. This provides reassurance that the study will be informative, i.

Use of methods for specifying the target difference in randomised controlled trial sample size calculations: Two surveys of trialists' practice.

Background: Central to the design of a randomised controlled trial (RCT) is a calculation of the number of participants needed. This is typically achieved by specifying a target difference, which enables the trial to identify a difference of a particular magnitude should one exist. Seven methods have been proposed for formally determining what the target difference should be.

Road traffic crashes and the protective effect of road curvature over small areas.

Road bends are known to cause traffic crashes, but the hypothesis in this study was that small geographical areas with many road bends have less, not more, road casualties than comparable areas with fewer bends. Data on road crashes involving fatal, serious and slight casualties in 571 wards in Eastern England were examined against four measures of average road curvature (mean angle per bend, cumulative angle per km, number of bends per km and ratio of road distance to straight distance) using regression analysis. Taking account of other risk factors, measures of average road curvature in wards were negatively associated with crash numbers, especially for fatal crashes.

Self-reported mental health-related quality of life and mortality in men and women in the European Prospective Investigation into Cancer (EPIC-Norfolk): a prospective population study.

Objective: To explore the relationship between self-reported mental functional health and mortality.

Methods: Participants included 17,777 men and women aged 40 to 79 years at baseline who lived in Norfolk, UK, and had no known cardiovascular disease or cancer, and completed the anglicized Short Form 36-item questionnaire (UK SF-36) during 1996 to 2000 in the European Prospective Investigation into Cancer-Norfolk prospective population study. We examined the relationship between mental functional health derived from the mental component summary scores of the SF-36 and mortality from all causes, cardiovascular disease, cancer, and other causes during an average 6.

Fruit and vegetable consumption and self-reported functional health in men and women in the European Prospective Investigation into Cancer-Norfolk (EPIC-Norfolk): a population-based cross-sectional study.

Objectives: To investigate the association between fruit and vegetable consumption and self-reported physical and mental functional health measured by an anglicised short-form 36-item questionnaire (UK SF-36).

Design: Population-based cross-sectional study.

Setting: General community in Norfolk, UK.

Modifiable lifestyle behaviors and functional health in the European Prospective Investigation into Cancer (EPIC)-Norfolk population study.

Objective: To examine the association between modifiable lifestyle behaviors and functional health.

Method: Population-based cross-sectional study in 16,678 men and women aged 40-79 years at baseline in 1993-1997 participating in the European Prospective Investigation into Cancer (EPIC)-Norfolk cohort.

Results: Smoking and physical inactivity were associated with poorer physical functional health, equivalent to being 7 years and 10-13 years older, respectively, and poorer mental functional health compared to non-smoking or being physically active.

Obesity indices and self-reported functional health in men and women in the EPIC-Norfolk.

Objective: To investigate the association between two indices of obesity, BMI and waist-to-hip ratio (WHR), and self-reported physical and mental functional health.

Research Methods And Procedures: We examined the relationship between obesity indices and self-reported physical and mental functional health measured by the Anglicized version of the Short-Form 36-item questionnaire in a population-based cross sectional study of 16,806 men and women 40 to 79 years old living in the general community in Norfolk, United Kingdom.

Results: Higher BMI and WHR were both independently associated with poorer self-reported physical functional health in men and women.

Impact of Helicobacter pylori eradication on dyspepsia, health resource use, and quality of life in the Bristol helicobacter project: randomised controlled trial.

Objective: To determine the impact of a community based Helicobacter pylori screening and eradication programme on the incidence of dyspepsia, resource use, and quality of life, including a cost consequences analysis.

Design: H pylori screening programme followed by randomised placebo controlled trial of eradication.

Setting: Seven general practices in southwest England.

Randomised controlled trial of effects of Helicobacter pylori infection and its eradication on heartburn and gastro-oesophageal reflux: Bristol helicobacter project.

Objectives: To investigate the effects of Helicobacter pylori infection and its eradication on heartburn and gastro-oesophageal reflux.

Design: Cross sectional study, followed by a randomised placebo controlled trial.

Setting: Seven general practices in Bristol, England.

Inverse relationship between alcohol consumption and active Helicobacter pylori infection: the Bristol Helicobacter project.

Objective: The aim of this study was to examine whether smoking or consumption of alcohol or coffee is associated with active Helicobacter pylori (H. pylori) infection.

Methods: This was a cross-sectional population study conducted as part of a randomized controlled trial of H.

Pulmonary rehabilitation compared with brief advice given for severe chronic obstructive pulmonary disease.

Purpose: The objective of this study was to compare the effectiveness of a short-term pulmonary rehabilitation program with brief advice given to patients with severe ventilatory impairment due to chronic obstructive pulmonary disease (COPD).

Methods: One hundred three patients with severe COPD, defined as having forced expiratory volume in 1 second < 40% predicted, were randomly assigned to rehabilitation or to brief advice. Fifty-four patients attended a rehabilitation program twice a week for 6 weeks.

A placebo-controlled randomized trial of eradication of Helicobacter pylori in the general population: study design and response rates of the Bristol Helicobacter Project.

The Bristol Helicobacter Project is an ongoing, pragmatic, double-blind placebo-controlled trial of the effect of Helicobacter pylori eradication on symptoms of dyspepsia, health utilization and costs, and quality of life in the adult population. Commencing in 1996, 27,536 individuals ages 20-59 years who were registered with seven primary care centers in Bristol and the surrounding areas in southwest England were invited to undergo a 13C urea breath test. There was no selection on the basis of symptoms and 23.