197,134 research outputs found
Questions asked and answered in pilot and feasibility randomized controlled trials
No full textAbstract Background In the last decade several authors have reviewed the features of pilot and feasibility studies and advised on the issues that should be addressed within them. We extend this literature by examining published pilot/feasibility trials that incorporate random allocation, examining their stated objectives, results presented and conclusions drawn, and comparing drug and non-drug trials. Methods A search of EMBASE and MEDLINE databases for 2000 to 2009 revealed 3652 papers that met our search criteria. A random sample of 50 was selected for detailed review. Results Most of the papers focused on efficacy: those reporting drug trials additionally addressed safety/toxicity; while those reporting non-drug trials additionally addressed methodological issues. In only 56% (95% confidence intervals 41% to 70%) were methodological issues discussed in substantial depth, 18% (95% confidence interval 9% to 30%) discussed future trials and only 12% (95% confidence interval 5% to 24%) of authors were actually conducting one. Conclusions Despite recent advice on topics that can appropriately be described as pilot or feasibility studies the large majority of recently published papers where authors have described their trial as a pilot or addressing feasibility do not primarily address methodological issues preparatory to planning a subsequent study, and this is particularly so for papers reporting drug trials. Many journals remain willing to accept the pilot/feasibility designation for a trial, possibly as an indication of inconclusive results or lack of adequate sample size.</p
The analysis of continuous outcomes in multi-centre trials with small centre sizes
No full textThe standard analysis of clinical trials stratified by centre is to include centres as fixed effects, but if many centres contribute small numbers of patients, this approach results in a loss of power. Assuming no treatment by centre interaction, we used simulation to examine power and coverage of confidence intervals from three approaches to the analysis of continuous outcome in multi-centre trials: ignoring centres, including centres as fixed effects, and including them as random effects. The simulation incorporated eight sizes of centre effects; randomization in blocks of size 2 or 4; and two sample sizes, namely 100 and 200 patients per treatment arm in a parallel groups design. All simulated data sets included many centres with few subjects. The three different approaches were unbiased and had similar coverage. Fixed effects analysis was less powerful, particularly when centre effects were small. Incorporating block randomization with larger block size increased non-orthogonality in the design, contributing to loss of power. Where centre effects are small and recruitment in many centres is low, the approaches of ignoring centres or incorporating them as random effects have better performance than the traditional fixed effects analysis
Graphical sensitivity analysis with different methods of imputation for a trial with probable non-ignorable missing data
No full textGraphical sensitivity analyses have recently been recommended for clinical trials with non-ignorable missing outcome. We demonstrate an adaptation of this methodology for a continuous outcome of a trial of three cognitive-behavioural therapies for mild depression in primary care, in which one arm had unexpectedly high levels of missing data. Fixed-value and multiple imputations from a normal distribution (assuming either varying mean and fixed standard deviation, or fixed mean and varying standard deviation) were used to obtain contour plots of the contrast estimates with their?P-values superimposed, their confidence intervals, and the root mean square errors. Imputation was based either on the outcome value alone, or on change from baseline. The plots showed fixed-value imputation to be more sensitive than imputing from a normal distribution, but the normally distributed imputations were subject to sampling noise. The contours of the sensitivity plots were close to linear in appearance, with the slope approximately equal to the ratio of the proportions of subjects with missing data in each trial arm
Wellcome Witnesses to Twentieth Century Medicine: Volume 1
No full textAnnotated and edited transcript of four Witness Seminars. Introduction by E M Tansey First published by the Wellcome Trust, 1997. ©The Trustee of the Wellcome Trust, London, 1997.In Volume One (Occasional Publication no. 4, 1997).All volumes are freely available online at: www.history.qmul.ac.uk/research/modbiomed/wellcome_witnesses/Annotated and edited transcript of four Witness Seminars. Introduction by E M Tansey.Annotated and edited transcript of four Witness Seminars. Introduction by E M Tansey.Annotated and edited transcript of four Witness Seminars. Introduction by E M Tansey.Annotated and edited transcript of four Witness Seminars. Introduction by E M Tansey.Four Witness Seminar transcripts of meetings held between 1993 and 1996: ‘Technology Transfer in Britain: The case of Monoclonal Antibodies’ (E M Tansey and P P Catterall, eds); ‘Self and Non-Self: A History of Autoimmunity’ (E M Tansey, S V Willhoft and D A Christie, eds); ‘Endogenous Opiates’ (E M Tansey and D A Christie, eds); ‘The Committee on Safety of Drugs’ (E M Tansey and L A Reynolds, eds). Introduction by E M Tansey, ‘What is a Witness Seminar’, separate index for each meeting. Tansey E M, Catterall P P, Christie D A, Willhoft S V, Reynolds L A. (eds) (1997) Wellcome Witnesses to Twentieth Century Medicine, volume 1. London: The Wellcome Trust.The Wellcome Trust is a registered charity, no. 210183
The comparability of community outcomes for european and non-european survivors of stroke in New Zealand
No full textAIMS: To measure community outcomes for stroke comparing European and non-European survivors.METHODS: This was a prospective, hospital-based study of consecutive patients admitted to three general hospitals in Wellington with acute stroke. Patients were assessed using a range of instruments for prestroke function, function while in hospital, and then followed for twelve months post-hospital discharge. Ethnicity was decided by self-report and Maori, Pacific people and Asians were grouped together as "non-Europeans" for analysis.RESULTS: 181 people with stroke were enrolled of whom 171 (94.5%) were followed up to death or twelve months post hospital discharge. 33 (18%) were non-European with 13 (7%) Maori, 14 (8%) Pacific people and 6 (3%) Asians. Non-European survivors at twelve months post hospital discharge were more likely to be dependent (corrected OR 21.0, 95% CI 3.1, 141), have significantly lower Functional Independence Measure scores, lower London Handicap Scores and lower scores on the Short Form 36 domains of physical functioning and vitality and Physical Component Summary score.CONCLUSIONS: Community outcomes for survivors of stroke may be worse for non-Europeans although this should be confirmed in a larger study
Duration of condition is unrelated to health-state valuation on the EuroQol
No full textOBJECTIVE: To determine whether health valuations, such as those used in economic evaluation, are affected by duration of a health condition. People with disabling health conditions tend to value health more highly than members of the general population, and one explanation for this is that over time their experience of living with a disabling illness changes the way in which they value health. If this is so, a relationship between the duration of an individual's disabling health condition and the valuation they assign to their health-state might reasonably be expected. DESIGN: A postal survey using the EuroQoL (EQ-5D) instrument to collect descriptions and valuations for health from people who reported a diagnosis of either stroke or multiple sclerosis. Contact with participants was made through national support organizations and questionnaires were returned by mail. RESULTS: Eight hundred and ninety-four people completed the survey. One hundred (11 %) had one health-state indicating moderate problems in all five dimensions of the EQ-5D descriptive profile. For people with this health-state, analysis of covariance showed no relationship between valuation of health-state and time from onset of illness (F = 0.38, p = 0.54). This finding applied irrespective of the diagnosis, and for some other less frequently reported health-states. CONCLUSION: Clinical experience suggests that over time people adapt to long-term disability. However we found no evidence to support the proposition that higher health-state valuations by people with disabling conditions are explained by the actual duration of their condition
Factors influencing rate of Barthel index change in hospital following stroke
No full textBACKGROUND AND PURPOSE: Randomized controlled trials of specific interventions in stroke rehabilitation are few. In using this study design to compare different rehabilitation interventions or different intensity of those interventions, measuring disability status at a fixed time point is one outcome option. In order for this approach to be valid, factors that might independently affect the speed of disability change have to be matched at baseline. We sought to investigate the impact of different factors on rate of disability change following stroke. METHODS: A prospective hospital-based study of consecutive patients admitted to each of three general hospitals in Wellington, New Zealand with acute stroke. Patients were assessed using the Barthel Index (BI, scored 0-20) within a few days of stroke and fortnightly until hospital discharge. Strokes were classified using the Oxfordshire Community Stroke Project classification. MAIN OUTCOME MEASURE: Barthel Index rate of change (BRC) computed from the difference between the first and last hospital BI scores divided by the time in weeks between these assessments. RESULTS: Of 104 subjects with two or more disability assessments in hospital, BRC was a mean 1.26 units per week (95% confidence interval (CI) 0.97, 1.56). The only factors significantly associated with BRC on univariate analysis were stroke type, pre-stroke Modified Rankin Scale (MRS) and pre-stroke London Handicap Score. In a general linear model analysis of covariance, stroke type (p = 0.015) and pre-stroke MRS (p < 0.001) remained significant. The mean BRC for lacunar infarcts (1.76 units per week, 95% CI 1.22, 2.30) was over three times that of total anterior circulation infarcts (0.48 units per week, 95% CI 0.20, 0.76). CONCLUSIONS: Future randomized controlled trials of rehabilitation interventions for stroke in hospitalized patients need to allow for pre-stroke level of dependence and stroke type in the study design, either excluding particular patients or ensuring even randomization of these key variables if speed of disability change is to be a valid outcome variabl
The combating obesity in M?ori and Pasifika adolescent school-children study: COMPASS methodology and study protocol
No full textCOMPASS will be used to provide direction for exercise prescription policy in at-risk M?ori and Pasifika adolescents
Avoiding pitfalls of correlation coefficients in the assessment of measurement instruments in rehabilitation research
No full textOBJECTIVE: To provide a practical guide on how to avoid the pitfalls of correlated correlation coefficients when comparing multiple instruments in rehabilitation research. DESIGN: An observational study comparing a number of instruments measuring quality of life (QoL) compared with an external criterion. SUBJECTS: Sixty-eight patients admitted to a rheumatology ward for intensive treatment of rheumatoid arthritis. METHODS: Patients completed three new (QoL) instruments and an established instrument before and after intensive treatment for rheumatoid arthritis. MAIN OUTCOME MEASURES: Correlation coefficients together with their confidence intervals and a test for the difference between a set of correlated correlation coefficients for the change in the EuroQoL Quality of Life scale (EuroQoL), the World Health Organization Quality Of Life-Abbreviated version (WHOQoL-BREF) and the Quality of Life Profile (QLP) against the Stanford Health Assessment Questionnaire (HAQ). RESULTS: Although the range of correlation between the new instruments and the external criterion was between -0.37 and -0.59 and suggested that one new instrument was far more responsive than the others, an omnibus test for an overall difference could find no difference in responsiveness. CONCLUSIONS: It is conceptually simple to use correlation coefficients to assess the properties of multiple instruments measured on the same subjects to find a 'best' instrument. However, proper interpretation of results when correlated correlation coefficients are calculated is complex. We recommend analysis includes: (a) that simple plots of the pairs of analysed variables are shown, (b) that simple linear model-fitting statistics, e.g., the R-squared statistic, accompany the plots, (c) that confidence intervals are presented for correlation coefficients, (d) that an omnibus statistical test for the difference between correlated correlation coefficients is presented, and (e) that normal model assumptions are teste
- …
