Biomedical subjects

Suezann Puffer

Publications and source records attributed to Suezann Puffer.

8 recordsLinked to original sources

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↗

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

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↗

PubMed2004

Health care costs of women with symptomatic vertebral fractures.

BACKGROUND: An important aspect of the economics of fracture prevention is averted fracture costs. However, while vertebral fractures represent a significant burden to society, quantifying their cost is difficult for several reasons. In this paper, we examine the health care costs of symptomatic vertebral fractures occurring in women aged 50 years and above in the UK. METHODS: We used a variety of data sources. The prevalence of pharmaceutical treatment for fracture prevention and number of general practitioner consultations, referrals, and hospital admissions associated with a diagnosis of vertebral fracture were identified from a case control study. For the unit cost of a general practitioner consultation, referral, and cost per inpatient day, we used 2002 data produced by the Personal Social Services Research Unit. Hospital Episode Statistics (HES) for 2001-2002 were used to estimate the median length of stay in hospital for women aged 50 years and above, and the Monthly Index of Medical Specialities (MIMS) was used to identify the costs of pharmaceutical treatments. Costs were discounted at 6%. RESULTS: From these data, we estimated that for the year prior and post diagnosis the average additional health care costs for those diagnosed with vertebral fracture were pounds 165, pounds 134, and pounds 2314 for general practitioner consultations, referrals, and hospital admissions, respectively (i.e., pounds 2613). The cost of pharmaceutical treatments prescribed for fracture prevention in the year following diagnosis was pound 97. DISCUSSION: Vertebral fractures are associated with significantly increased health care costs. These costs need to be set against the costs of fracture prevention.

Aged↗

PubMed2004

Practice nurses' intentions to use clinical guidelines.

BACKGROUND: Evidence indicates that, although nurses are increasingly using clinical guidelines to ensure higher quality of care, there is a wide variance in their adherence to them. The utility of the Theory of Planned Behaviour (TPB) has not been previously investigated in explaining this variance in community nursing. AIM: This paper reports a study whose primary aim was to examine the utility of the TPB in explaining variations in practice nurses' intentions to offer smoking cessation advice in accordance with coronary heart disease guidelines. METHODS: A cross-sectional survey using a postal questionnaire was carried out. A 52-item questionnaire was administered to 48 practice nurses in England. The questionnaire was designed to assess the components of the TPB, and included measures of intentions to offer smoking cessation advice, self-reported past behaviour, attitudes, subjective norms, perceived behavioural controls (PBCs), behavioural beliefs and evaluations, normative beliefs and motivation to comply, and control beliefs and evaluations. RESULTS: The TPB explained up to 40% of variance in intentions to offer smoking cessation advice. Attitudes and PBCs were the most important predictors of intention. Among other elements of the TPB, indirect attitudes and indirect PBCs made significant positive contributions to explaining variance in intention. DISCUSSION: Future trials of interventions to increase practice nurses' adherence to clinical guidelines could attempt to address the elements identified in this study as important factors. Further studies are required to examine the utility of the TPB in predicting practice nurses' behaviour.

Adult↗

PubMed2004

Increasing response rates to postal questionnaires: a randomised trial of variations in design.

OBJECTIVES: Low response rates to postal questionnaires can threaten the validity of studies by reducing the effective sample size and introducing bias. The identification of methods with which to optimise response rates could, therefore, improve the quality of studies. In an attempt to identify such methods, we undertook a randomised trial of two simple variations in questionnaire design. METHODS: Using a 2 x 2 factorial design, we conducted a randomised trial to test two variations in questionnaire design; the questionnaires were printed on either single-sided or double-sided paper and had either a single- or multiple-booklet layout. Using equal random allocation, 3836 women were randomised to receive one of these questionnaires as part of a study investigating risk factors for osteoporotic fractures. RESULTS: One thousand eight hundred and seventy questionnaires were returned, giving an overall response rate of 48.7%. There were no significant differences in the overall response to each of the four questionnaire designs. When the number of responders who completed at least 50% of each of the three sections was identified, it was found that single-booklet questionnaires had a better response than the multiple-booklet questionnaires and that single-sided questionnaires had a better response than double-sided questionnaires. However, these results were not significant at the 5% level. There were no significant differences in the response to questions on the odd (left-hand side) pages for the single- compared with the double-sided questionnaires. CONCLUSION: As the most cost-effective use of resources, we would advocate the use of double- rather than single-sided questionnaires, and use of a single- rather than multiple-booklet design.

Aged↗

PubMed2003

Evidence for risk of bias in cluster randomised trials: review of recent trials published in three general medical journals.

OBJECTIVE: To examine the prevalence of a risk of bias associated with the design and conduct of cluster randomised controlled trials among a sample of recently published studies. DESIGN: Retrospective review of cluster randomised trials published in the BMJ, Lancet, and New England Journal of Medicine from January 1997 to October 2002. MAIN OUTCOME MEASURES: Prevalence of secure randomisation of clusters, identification of participants before randomisation (to avoid foreknowledge of allocation), differential recruitment between treatment arms, differential application of inclusion and exclusion criteria, and differential attrition. RESULTS: Of the 36 trials identified, 24 were published in the BMJ,11 in the Lancet, and a single trial in the New England Journal of Medicine. At the cluster level, 15 (42%) trials provided evidence for secure allocation and 25 (69%) used stratified allocation. Few trials showed evidence of imbalance at the cluster level. However, some evidence of susceptibility to risk of bias at the individual level existed in 14 (39%) studies. CONCLUSIONS: Some recently published cluster randomised trials may not have taken adequate precautions to guard against threats to the internal validity of their design.

Bias↗