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David J Torgerson

Publications and source records attributed to David J Torgerson.

At least 19 recordsLinked to original sources
PubMed2006

Increasing recruitment to randomised trials: a review of randomised controlled trials.

BACKGROUND: Poor recruitment to randomised controlled trials (RCTs) is a widespread and important problem. With poor recruitment being such an important issue with respect to the conduct of randomised trials, a systematic review of controlled trials on recruitment methods was undertaken in order to identify strategies that are effective. METHODS: We searched the register of trials in Cochrane library from 1996 to end of 2004. We also searched Web of Science for 2004. Additional trials were identified from personal knowledge. Included studies had to use random allocation and participants had to be allocated to different methods of recruitment to a 'real' randomised trial. Trials that randomised participants to 'mock' trials and trials of recruitment to non-randomised studies (e.g., case control studies) were excluded. Information on the study design, intervention and control, and number of patients recruited was extracted by the 2 authors. RESULTS: We identified 14 papers describing 20 different interventions. Effective interventions included: telephone reminders; questionnaire inclusion; monetary incentives; using an 'open' rather than placebo design; and making trial materials culturally sensitive. CONCLUSION: Few trials have been undertaken to test interventions to improve trial recruitment. There is an urgent need for more RCTs of recruitment strategies.

Culture↗
PubMed2006

Vitamin K and the prevention of fractures: systematic review and meta-analysis of randomized controlled trials.

BACKGROUND: Observational and some experimental data suggest that low intake of vitamin K may be associated with an increased risk of fracture. OBJECTIVE: To assess whether oral vitamin K (phytonadione and menaquinone) supplementation can reduce bone loss and prevent fractures. DATA SOURCES: The search included the following electronic databases: MEDLINE (1966 to June 2005), EMBASE (1980 to June 2005), the Cochrane Library (issue 2, 2005), the ISI Web of Science (1945 to June 2005), the National Research Register (inception to the present), Current Controlled Trials, and the Medical Research Council Research Register. STUDY SELECTION: Randomized controlled trials that gave adult participants oral phytonadione and menaquinone supplements for longer than 6 months were included in this review. DATA EXTRACTION: Four authors extracted data on changes in bone density and type of fracture. All articles were double screened and double data extracted. DATA SYNTHESIS: Thirteen trials were identified with data on bone loss, and 7 reported fracture data. All studies but 1 showed an advantage of phytonadione and menaquinone in reducing bone loss. All 7 trials that reported fracture effects were Japanese and used menaquinone. Pooling the 7 trials with fracture data in a meta-analysis, we found an odds ratio (OR) favoring menaquinone of 0.40 (95% confidence interval [CI], 0.25-0.65) for vertebral fractures, an OR of 0.23 (95% CI, 0.12-0.47) for hip fractures, and an OR of 0.19 (95% CI, 0.11-0.35) for all nonvertebral fractures. CONCLUSIONS: This systematic review suggests that supplementation with phytonadione and menaquinone-4 reduces bone loss. In the case of the latter, there is a strong effect on incident fractures among Japanese patients.

Bone Density↗
PubMed2006

Review of randomised trials using the post-randomised consent (Zelen's) design.

BACKGROUND: In 1979, Zelen described a trial method of randomising participants before acquiring consent in order to enhance recruitment to clinical trials. The method has been criticised ethically due to lack of consent and scientifically due to high crossover rates. This paper reviews recent published trials using this method and describes the reasons authors gave for using the method, examines the crossover rates, and looks at the quality of identified trials. METHODS: Literature review searching for all citations to the relevant Zelen's papers of trials published since 1990 plus inclusion of trials from personal knowledge. RESULTS: We identified 58 relevant trials. The most common justification for the use of Zelen method was to avoid the introduction of bias (e.g., to avoid the Hawthorne effect). Few trialists had explicitly used the design to enhance participant recruitment. Most trials (n=41) experienced some crossover from one group to the other (median crossover=8.9%, mean=13.8%, IQR 2.6% to 15%) although this was usually within acceptable limits. CONCLUSION: The most important reason stated by authors for using Zelen's method was to limit bias. Zelen's method, if carefully used, can avoid 'resentful demoralisation' and the Hawthorne effect biasing a trial. Unlike a previous review, we found that crossover was not a problem for most trials.

Cross-Over Studies↗
PubMed2006

Randomized trial of a brief physiotherapy intervention compared with usual physiotherapy for neck pain patients: cost-effectiveness analysis.

OBJECTIVES: To assess the cost-effectiveness of brief physiotherapy intervention versus usual physiotherapy management in patients with neck pain of musculoskeletal origin in the community setting. METHODS: A cost-effectiveness analysis was conducted alongside a multicenter pragmatic randomized controlled clinical trial. Individuals 18 years of age and older with neck pain of more than 2 weeks were recruited from physiotherapy departments with referrals from general practitioners (GPs) in the East Yorkshire and North Lincolnshire regions in the United Kingdom. A total of 139 patients were allocated to the brief intervention, and 129 to the usual physiotherapy. Resource use data were prospectively collected on the number of physiotherapy sessions, hospital stay, specialist, and GP visits. Quality-adjusted life years (QALYs) were estimated using EQ-5D data collected at baseline, 3 and 12 months from the start of the treatment. The economic evaluation was conducted from the U.K. National Health System perspective. RESULTS: On average, brief intervention produced lower costs (pounds--68; 95 percent confidence interval [CI], pounds--103 to pounds--35) and marginally lower QALYs (-0.001; 95 percent CI, -0.030 to 0.028) compared with usual physiotherapy, resulting in an incremental cost per QALY of pounds 68,000 for usual physiotherapy. These results are sensitive to patients' treatment preferences. CONCLUSIONS: Usual physiotherapy may not be good value for money for the average individual in this trial but could be a cost-effective strategy for those who are indifferent toward which treatment they receive.

Cost-Benefit Analysis↗
PubMed2006

A systematic review of the effects of calcium supplementation on body weight.

Animal studies and epidemiological studies have suggested that Ca supplementation (with Ca supplements or dairy products) may be associated with weight loss in human adults. We aimed to assess whether any association was present by reviewing relevant randomized controlled trials in human subjects. The study was a systematic review and subsequent meta-analysis of randomized controlled trials that used Ca supplementation as an intervention in persons 18 or more years of age, and that reported body weight as a final outcome. A total of thirteen randomized controlled trials were included in the meta-analysis. There was no association between the increased consumption of either Ca supplements or dairy products and weight loss after adjusting for differences in baseline weights between the control and intervention groups (P=0.19 and 0.85, respectively). We therefore concluded that Ca supplementation has no statistically significant association with a reduction in body weight.

Adult↗
PubMed2005

A randomised controlled trial to assess the effectiveness of offering study results as an incentive to increase response rates to postal questionnaires [ISRCTN26118436].

BACKGROUND: Postal questionnaires are widely used to collect outcome data on participants. However, a poor response to questionnaires will reduce the statistical power of the study and may introduce bias. A meta analysis of ten trials offering study results, largely in the fields of education and marketing, was shown to be ineffective, with the odds ratio for response with offering research findings is 0.92 (95% CI 0.75 to 1.11). However uncertainty still exists as it is uncertain whether results from such trials can be extrapolated to that of a health care setting. The aim of this study was to assess whether offering participants study results increases the response rates to postal questionnaires. METHODS: 1038 women aged over 70 years were remotely randomised by computer in a 3:1 ratio. 250 participants did not receive the offer of knowing the results of the trial and 788 participants were offered the results of the trial in a postal questionnaire. The main outcome measure was response rate. Chi square test was used to evaluate the overall differences in response rate between the two groups. An adjusted analysis, adjusting for whether the participant was taking calcium and age was also undertaken. RESULTS: The response rates were not significantly different Odds Ratio 0.88 (95% confidence intervals 0.48 to 1.63) p = 0.69. CONCLUSION: Offering study results to women living in the community aged over 70 does not increase response rates to postal questionnaires. Although researchers have an ethical obligation to offer participants study results, since 10% of women did not wish to receive the results, investigators should give participants the option to opt out of receiving the study's results.

Aged↗
PubMed2005

A randomized trial comparing a group exercise programme for back pain patients with individual physiotherapy in a severely deprived area.

PURPOSE: To compare a group exercise programme known as the Back to Fitness programme with individual physiotherapy for patients with non-specific low back pain from a materially deprived area. METHOD: This was a randomized controlled trial including 237 physiotherapy patients with back pain lasting more than six weeks. Participants were allocated to either the Back to Fitness programme or to individual physiotherapy, and followed up at three months and 12 months after randomization. The main outcome measure was the Roland Disability Questionnaire. Secondary measures were: SF12, EQ5D, Pain Self-Efficacy Scale. Health care diaries recording patients' use of health care resources were also collected over a 12-month period. RESULTS: There were no statistically significant differences in change scores between groups on the primary outcome measure at three months (CI - 2.24 to 0.49) and at 12 months (CI - 1.68 to 1.39). Only minor improvements in disability scores were observed in the Back to Fitness group at three months and 12 months respectively (mean change scores; - 0.89, - 0.77) and in the individual physiotherapy arm (mean change scores; - 0.02, - 0.63). Further analysis showed that patients from the most severely deprived areas were marginally worse at three month follow-up whereas those from more affluent areas tended to improve (CI 0.43 to 3.15).

Adult↗
PubMed2005

Economic evaluations of interventions for the prevention and treatment of osteoporosis: a structured review of the literature.

Economic evaluations are increasingly being used by decision-makers to estimate the cost-effectiveness of interventions. The objective of this study was to conduct a structured review of economic evaluations of interventions to prevent and treat osteoporosis. Articles were identified independently by two reviewers through searches on MEDLINE, the bibliographies of reviews and identified economic models, and expert opinion, using predefined inclusion and exclusion criteria. Data on country, type and level of interventions, type of fractures, interventions, study population and the authors' stated conclusions were extracted. Forty-two relevant studies were identified. The majority of studies (71%) were conducted in Sweden, the UK and the US. The main interventions investigated were hormone replacement therapy (27%), bisphosphonates (17%) and combinations of vitamin D and calcium (16%). In 38% of studies, hip fracture was the sole fracture outcome. Eighty-eight percent (88%) of studies investigated female populations only. A relatively large number of economic evaluations were identified in the field of osteoporosis. Major changes have recently occurred in the treatment of this disease, following the publication of the results of the Women's Health Initiative trial. Methodological developments in economic evaluations, such as the use of probabilistic sensitivity analysis and cost-effectiveness acceptability curves, have also taken place. Such changes are reflected in the studies that were reviewed. The development of economic models should be an iterative process that incorporates new information, whether clinical or methodological, as it becomes available.

Aged↗
PubMed2005

Randomised controlled trial of calcium and supplementation with cholecalciferol (vitamin D3) for prevention of fractures in primary care.

OBJECTIVE: To assess whether supplementation with calcium and cholecaliferol (vitamin D3) reduces the risk of fracture in women with one or more risk factors for fracture of the hip. DESIGN: Pragmatic open randomised controlled trial. SETTING: Practice nurse led clinics in primary care. PARTICIPANTS: 3314 women aged 70 and over with one or more risk factors for hip fracture: any previous fracture, low body weight (< 58 kg), smoker, family history of hip fracture, or fair or poor self reported health. INTERVENTION: Daily oral supplementation using 1000 mg calcium with 800 IU cholecaliferol and information leaflet on dietary calcium intake and prevention of falls, or leaflet only (control group). MAIN OUTCOME MEASURES: Primary outcome measure was all clinical fractures and secondary outcome measures were adherence to treatment, falls, and quality of life (measured with the SF-12). RESULTS: 69% of the women who completed the follow-up questionnaire at 24 months were still taking supplements (55% with inclusion of randomised participants known to be alive). After a median follow-up of 25 months (range 18 to 42 months), clinical fracture rates were lower than expected in both groups but did not significantly differ for all clinical fractures (odds ratio for fracture in supplemented group 1.01, 95% confidence interval 0.71 to 1.43). The odds ratio for hip fracture was 0.75 (0.31 to 1.78). The odds of a woman having a fall at six and 12 months was 0.99 and 0.98, respectively. Quality of life did not significantly differ between the groups. CONCLUSION: We found no evidence that calcium and vitamin D supplementation reduces the risk of clinical fractures in women with one or more risk factors for hip fracture. Registration ISRCTN26118436, controlled trials registry.

Administration, Oral↗
PubMed2005

Methodological bias in cluster randomised trials.

BACKGROUND: Cluster randomised trials can be susceptible to a range of methodological problems. These problems are not commonly recognised by many researchers. In this paper we discuss the issues that can lead to bias in cluster trials. METHODS: We used a sample of cluster randomised trials from a recent review and from a systematic review of hip protectors. We compared the mean age of participants between intervention groups in a sample of 'good' cluster trials with a sample of potentially biased trials. We also compared the effect sizes, in a funnel plot, between hip protector trials that used individual randomisation compared with those that used cluster randomisation. RESULTS: There is a tendency for cluster trials, with evidence methodological biases, to also show an age imbalance between treatment groups. In a funnel plot we show that all cluster trials show a large positive effect of hip protectors whilst individually randomised trials show a range of positive and negative effects, suggesting that cluster trials may be producing a biased estimate of effect. CONCLUSION: Methodological biases in the design and execution of cluster randomised trials is frequent. Some of these biases associated with the use of cluster designs can be avoided through careful attention to the design of cluster trials. Firstly, if possible, individual allocation should be used. Secondly, if cluster allocation is required, then ideally participants should be identified before random allocation of the clusters. Third, if prior identification is not possible, then an independent recruiter should be used to recruit participants.

Age Factors↗
PubMed2005

Regression to the mean: treatment effect without the intervention.

Regression to the mean (RTM) is a widespread statistical phenomenon. It is a group phenomenon that occurs whenever an extreme group is selected from a population based on the measurement of a particular variable. If a second measurement is then taken for the same group, the second mean will be closer to the population mean than the first measurement. This decrease (or increase) can be mistakenly attributed to a treatment effect; the conclusion can be drawn that an effect results from treatment when it in fact results from chance. Any intervention that is aimed at a group or characteristic that is very different from the average will appear to be successful because of RTM. It is therefore important that any genuine reductions because of the treatment are separated out from the effect of RTM. If the problem is ignored then this will lead to errors in the interpretation of results and, potentially, decisions made on the evidence of those results. This paper highlights the importance of the issue and its effects on many common clinical, public health and managerial decisions.

Bone Density↗
PubMed2005

Cluster randomized controlled trials.

Cluster randomized controlled trial (RCT), in which groups or clusters of individuals rather than individuals themselves are randomized, are increasingly common. Indeed, for the evaluation of certain types of intervention (such as those used in health promotion and educational interventions) a cluster randomized trial is virtually the only valid approach. However, cluster trials are generally more difficult to design and execute than individually randomized studies, and some design features of a cluster trial may make it particularly vulnerable to a range of threats that can introduce bias. In this paper we discuss the issues that can lead to bias in cluster randomized trials and conclude with some suggestions for avoiding these problems.

Cluster Analysis↗