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Search Results: 1 - 10 of 318434 matches for " Martin J. Bland "
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Teaching statistics to medical students using problem-based learning: the Australian experience
J Martin Bland
BMC Medical Education , 2004, DOI: 10.1186/1472-6920-4-31
Abstract: All Australian medical schools using PBL were visited, with two exceptions. Teachers of statistics and medical education specialists were interviewed. For schools which were not visited, information was obtained by email.No Australian medical school taught statistics and research methods in a totally integrated way, as part of general PBL teaching. In some schools, statistical material was integrated but taught separately, using different tutors. In one school, PBL was used only for 'public health' related subjects. In some, a parallel course using more traditional techniques was given alongside the PBL teaching of other material. This model was less successful than the others.There are several difficulties in implementing an integrated approach. However, not integrating is detrimental to statistics and research methods teaching, which is of particular concern in the age of evidence-based medicine. Some possible ways forward are suggested.Problem-based learning (PBL) is a method of teaching and learning which is widely used in the education of medical students [1,2]. In problem-based learning, students working in a small group are presented with a problem, typically a description of a patient presentation. They decide what features of the problem are outside their present knowledge and divide these topics between them. They then research their topics using library and internet material and report back to the next small group tutorial with their findings. In a problem-based learning curriculum, this is the principal method of learning. More traditional methods, such as lectures and practical exercises, provide background and support material. An example of a PBL teaching problem is given in the Appendix.This project was conceived at a meeting of statisticians from UK medical schools, which is held every year at the Burwalls conference centre, University of Bristol. In 2002, one of the topics for discussion was problem-based learning (PBL). Several things became appar
Cluster randomised trials in the medical literature: two bibliometric surveys
J Martin Bland
BMC Medical Research Methodology , 2004, DOI: 10.1186/1471-2288-4-21
Abstract: Computer search for papers on cluster randomised trials since 1980, hand search of trial reports published in selected volumes of the British Medical Journal over 20 years.There has been a large increase in the numbers of methodological papers and of trial reports using the term 'cluster random' in recent years, with about equal numbers of each type of paper. The British Medical Journal contained more such reports than any other journal. In this journal there was a corresponding increase over time in the number of trials where subjects were randomised in clusters. In 2003 all reports showed awareness of the need to allow for clustering in the analysis. In 1993 and before clustering was ignored in most such trials.Cluster trials are becoming more frequent and reporting is of higher quality. Perhaps statistician pressure works.Cluster randomised trials are those where research subjects are not allocated to treatments independently, but as a group. For example, in a study of counselling patients on physical activity in general practice, practices were allocated to counselling or control and patients aged 40–79 years who attended during a five day period and who did not take regular exercise were invited to take part. Patients in the same practice received the same treatment, counselling or usual care, depending on how the practice was allocated. [1] The group of patients within the general practice formed a cluster.Members of a cluster will be more like one another than they are like members of other clusters and we need to take this into account in the analysis, and preferably the design, of the study. Methods which ignore clustering may mislead, because they assume that all subjects provide independent observations. Applying simple statistical methods to such data, without taking the clustering into account, can lead to confidence intervals which are too narrow and P values which are too small.There has been an increasing interest in cluster randomised trials over th
Validating HeartSmart® against the Cardiopulmonary Bypass Machine  [PDF]
Kenneth J. Warring-Davies, Martin J. Bland
Surgical Science (SS) , 2012, DOI: 10.4236/ss.2012.31004
Abstract: Purpose: To assess the utility of HeartSmart?, a new method that uses empirical physiological formulae to estimate hemodynamic variables, in estimating cardiac index during open heart surgery when compared with the cardiopulmonary bypass machine. Methods: This was a prospective, blinded study of patients undergoing elective cardiac bypass surgery. We monitored and compared the flow rates provided by the cardiopulmonary bypass machine (roller pump) with estimates derived from the empirical physiological formulae embedded in the HeartSmart? monitor in 32 patients. Cardiac index values were compared at the start of cardiopulmonary bypass, during re-warming, and at the end of cardiopulmonary bypass. Results: A total of 256 paired sets of measurements were suitable for comparison. The mean of the differences or bias (95% limits of agreement) was 0.09 l/min/m2 and the limits of agreement –0.86 to 1.05 l/min/m2. The mean difference of the sets of 256 measurements was 585.5 l/min/m for the pump and 575.0 l/min/m2 for the empirical physiological formulae—a difference of 5% l/min/m2. The range of flow rates for the pump was 1.2 to 2.85 l/min/m2; for the empirical physiological formulae, the range was 1.2 to 3.0 l/min/m2. Conclusion: The cardiac index estimates derived from the empirical physiological formulae in the HeartSmart? software are in good agreement with pump cardiac output rates. These results suggest that HeartSmart? measurements are sufficiently accurate for assessing hemodynamic variables in many groups of patients.
Comparisons against baseline within randomised groups are often used and can be highly misleading
J Martin Bland, Douglas G Altman
Trials , 2011, DOI: 10.1186/1745-6215-12-264
Abstract: We give several examples where this has been done. We use simulation to demonstrate that the procedure is invalid and also show this algebraically.This approach is biased and invalid, producing conclusions which are, potentially, highly misleading. The actual alpha level of this procedure can be as high as 0.50 for two groups and 0.75 for three.Randomised groups should be compared directly by two-sample methods and separate tests against baseline are highly misleading.When we randomise trial participants into two or more groups, we do this so that they will be comparable in every respect except the intervention which they then receive. The essence of a randomised trial is to compare the outcomes of groups of individuals that start off the same. We expect to see an estimate of the difference (the "treatment effect") with a confidence interval and, often, a P value. However, rather than comparing the randomised groups directly, researchers sometimes look within groups at the change between the outcome measure from pre-intervention baseline to the final measurement at the end of the trial. They then perform a test of the null hypothesis that the mean difference is zero, separately in each randomised group. They may then report that in one group this difference is significant but not in the other and conclude that this is evidence that the groups, and hence the treatments, are different.For example, a recent trial received wide media publicity as the first "anti-ageing" cream "proven" to work in a randomised controlled clinical trial [1]. Participants were randomised into two groups, to receive either the "anti-ageing" product or the vehicle as a placebo. Among other measures, the authors report the appearance of fine lines and wrinkles, measured on a scale of 0 to 8, at baseline and after six months.The authors gave the results of significance tests comparing the score with baseline for each group separately, reporting the active treatment group to have a significant d
Acupuncture for chronic neck pain: a pilot for a randomised controlled trial
Gemma C Salter, Mark Roman, Martin J Bland, Hugh MacPherson
BMC Musculoskeletal Disorders , 2006, DOI: 10.1186/1471-2474-7-99
Abstract: Patients whose GPs had diagnosed neck pain were recruited from one general practice, and randomised to receive usual GP care only, or acupuncture (up to 10 treatments over 3 months) as an adjunctive treatment to usual GP care. The primary outcome measure was the Northwick Park Neck Pain Questionnaire (NPQ) at 3 months. The primary analysis was to determine the sample size for the full scale study.Of the 227 patients with neck pain identified from the GP database, 28 (12.3%) consenting patients were eligible to participate in the pilot and 24 (10.5%) were recruited to the trial. Ten patients were randomised to acupuncture, receiving an average of eight treatments from one of four acupuncturists, and 14 were randomised to usual GP care alone. The sample size for the full scale trial was calculated from a clinically meaningful difference of 5% on the NPQ and, from this pilot, an adjusted standard deviation of 15.3%. Assuming 90% power at the 5% significance level, a sample size of 229 would be required in each arm in a large-scale trial when allowing for a loss to follow-up rate of 14%. In order to achieve this sample, one would need to identify patients from databases of GP practices with a total population of 230,000 patients, or approximately 15 GP practices roughly equal in size to the one involved in this study (i.e. 15,694 patients).This pilot study has allowed a number of recommendations to be made to facilitate the design of a large-scale trial, which in turn will help to clarify the existing evidence base on acupuncture for neck pain.It is estimated that during the course of a year, approximately 34% of adults experience neck pain, of which a significant proportion is chronic, with about 14% experiencing neck pain for at least six months duration [1]. As well as the impact it has on individuals at a personal level, there are also significant financial costs associated with neck pain [2]. In general, evidence is lacking to support many standard treatments for c
Acupuncture for irritable bowel syndrome: primary care based pragmatic randomised controlled trial
MacPherson Hugh,Tilbrook Helen,Bland J Martin,Bloor Karen
BMC Gastroenterology , 2012, DOI: 10.1186/1471-230x-12-150
Abstract: Background Acupuncture is used by patients as a treatment for irritable bowel syndrome (IBS) but the evidence on effectiveness is limited. The purpose of the study was to evaluate the effectiveness of acupuncture for irritable bowel syndrome in primary care when provided as an adjunct to usual care. Methods Design: A two-arm pragmatic randomised controlled trial. Setting: Primary care in the United Kingdom. Patients: 233 patients had irritable bowel syndrome with average duration of 13 years and score of at least 100 on the IBS Symptom Severity Score (SSS). Interventions: 116 patients were offered 10 weekly individualised acupuncture sessions plus usual care, 117 patients continued with usual care alone. Measurements: Primary outcome was the IBS SSS at three months, with outcome data collected every three months to 12 months. Results There was a statistically significant difference between groups at three months favouring acupuncture with a reduction in IBS Symptom Severity Score of 27.43 (95% CI: –48.66 to 6.21, p = 0.012). The number needed to treat for successful treatment (≥50 point reduction in the IBS SSS) was six (95% CI: 3 to 17), based on 49% success in the acupuncture group vs. 31% in the control group, a difference between groups of 18% (95% CI: 6% to 31%). This benefit largely persisted at 6, 9 and 12 months. Conclusions Acupuncture for irritable bowel syndrome provided an additional benefit over usual care alone. The magnitude of the effect was sustained over the longer term. Acupuncture should be considered as a treatment option to be offered in primary care alongside other evidenced based treatments. Trial Registration Current Controlled Trials ISRCTN08827905
Copper Bracelets and Magnetic Wrist Straps for Rheumatoid Arthritis – Analgesic and Anti-Inflammatory Effects: A Randomised Double-Blind Placebo Controlled Crossover Trial
Stewart J. Richmond, Shalmini Gunadasa, Martin Bland, Hugh MacPherson
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0071529
Abstract: Background Folklore remedies for pain and inflammation in rheumatoid arthritis include the application of magnets and copper to the skin. Despite the popular use of devices containing magnets or copper for this purpose, little research has been conducted to evaluate the efficacy of such treatments. Objective To investigate whether the practice of wearing magnetic wrists straps, or copper bracelets, offers any specific therapeutic benefit for patients with rheumatoid arthritis. Design Randomised double-blind placebo-controlled crossover trial. Methods 70 patients, aged 33 to 79 years and predominantly female (n = 52), with painful rheumatoid arthritis were recruited from general practices within Yorkshire. Participants were randomly allocated to wear four devices in a different order. Devices tested were: a standard (1502 to 2365 gauss) magnetic wrist strap, a demagnetised (<20 gauss) wrist strap, an attenuated (250 to 350 gauss) magnetic wrist strap, and a copper bracelet. Devices were each worn for five weeks, with treatment phases being separated by one week wash-out periods. The primary outcome measured was pain using a 100 mm visual analogue scale. Secondary pain measures were the McGill Pain Questionnaire and tender joint count. Inflammation was assessed using C-reactive protein and plasma viscosity blood tests and by swollen joint count. Physical function was assessed using the Health Assessment Questionnaire (Disability Index). Disease activity and medication use was also measured. Results 65 participants provided complete self-report outcome data for all devices, four participants provided partial data. Analysis of treatment outcomes did not reveal any statistically significant differences (P>0.05) between the four devices in terms of their effects on pain, inflammation, physical function, disease activity, or medication use. Conclusions Wearing a magnetic wrist strap or a copper bracelet did not appear to have any meaningful therapeutic effect, beyond that of a placebo, for alleviating symptoms and combating disease activity in rheumatoid arthritis. Trial Registration Controlled-Trials.com ISRCTN51459023 ISRCTN51459023.
Do Baseline P-Values Follow a Uniform Distribution in Randomised Trials?
Martin Bland
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0076010
Abstract: Background The theory has been put forward that if a null hypothesis is true, P-values should follow a Uniform distribution. This can be used to check the validity of randomisation. Method The theory was tested by simulation for two sample t tests for data from a Normal distribution and a Lognormal distribution, for two sample t tests which are not independent, and for chi-squared and Fisher’s exact test using small and using large samples. Results For the two sample t test with Normal data the distribution of P-values was very close to the Uniform. When using Lognormal data this was no longer true, and the distribution had a pronounced mode. For correlated tests, even using data from a Normal distribution, the distribution of P-values varied from simulation run to simulation run, but did not look close to Uniform in any realisation. For binary data in a small sample, only a few probabilities were possible and distribution was very uneven. With a sample of two groups of 1,000 observations, there was great unevenness in the histogram and a poor fit to the Uniform. Conclusions The notion that P-values for comparisons of groups using baseline data in randomised clinical trials should follow a Uniform distribution if the randomisation is valid has been found to be true only in the context of independent variables which follow a Normal distribution, not for Lognormal data, correlated variables, or binary data using either chi-squared or Fisher’s exact tests. This should not be used as a check for valid randomisation.
The large scale distribution of warm ionized gas around nearby radio galaxies with jet-cloud interactions
C. N. Tadhunter,M. Villar-Martin,R. Morganti,J. Bland-Hawthorn,D. Axon
Physics , 2000, DOI: 10.1046/j.1365-8711.2000.03416.x
Abstract: Deep, narrow-band Halpha observations taken with the TAURUS Tunable Filter (TTF) on the 4.2m WHT telescope are presented for two nearby radio galaxies with strong jet-cloud interactions. Although the brightest emission line components are closely aligned with the radio jets --- providing nearby examples of the ``alignment effect'' most commonly observed in high redshift (z > 0.5) radio galaxies --- lower surface brightness emission line structures are detected at large distances (10's of kpc) from the radio jet axis. These latter structures cannot be reconciled with anisotropic illumination of the ISM by obscured quasar-like sources, since parts of the structures lay outside any plausible quasar ionization cones. Rather, the distribution of the emission lines around the fringes of the extended radio lobes suggests that the gas is ionized either by direct interaction with the radio components, or by the diffuse photoionizing radiation fields produced in the shocks generated in such interactions. These observations serve to emphasise that the ionizing effects of the radio components can extend far from the radio jet axes, and that deep emission line imaging observations are required to reveal the true distribution of warm gas in the host galaxies. We expect future deep imaging observations to reveal similar structures perpendicular to the radio axes in the high-z radio galaxies.
Controllable non-local interactions between dark solitons in dipolar condensates
T. Bland,M. J. Edmonds,N. P. Proukakis,A. M. Martin,D. H. J. O'Dell,N. G. Parker
Physics , 2015, DOI: 10.1103/PhysRevA.92.063601
Abstract: We study the family of static and moving dark solitons in quasi-one-dimensional dipolar Bose-Einstein condensates, exploring their modified form and interactions. The density dip of the soliton acts as a giant anti-dipole which adds a non-local contribution to the conventional local soliton-soliton interaction. We map out the stability diagram as a function of the strength and polarization direction of the atomic dipoles, identifying both roton and phonon instabilities. Away from these instabilities, the solitons collide elastically. Varying the polarization direction relative to the condensate axis enables tuning of this non-local interaction between repulsive and attractive; the latter case supports unusual dark soliton bound states. Remarkably, these bound states are themselves shown to behave like solitons, emerging unscathed from collisions with each other.
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