(1/116) The requirement for prior consent to participate on survey response rates: a population-based survey in Grampian.
BACKGROUND: A survey was carried out in the Grampian region of Scotland with a random sample of 10,000 adults registered with a General Practitioner in Grampian. The study complied with new legislation requiring a two-stage approach to identify and recruit participants, and examined the implications of this for response rates, non-response bias and speed of response. METHODS: A two-stage survey was carried out consistent with new confidentiality guidelines. Individuals were contacted by post and asked by the Director of Public Health to consent to receive a postal or electronic questionnaire about communicating their views to the NHS. Those who consented were then sent questionnaires. Response rates at both stages were measured. RESULTS: 25% of people returned signed consent forms and were invited to complete questionnaires. Respondents at the consent stage were more likely to be female (odds ratio (OR) response rate of women compared to men = 1.5, 95% CI 1.4, 1.7), less likely to live in deprived postal areas (OR = 0.59, 95% CI 0.45, 0.78) and more likely to be older (OR for people born in 1930-39 compared to people born in 1970-79 = 2.82, 95% CI 2.36, 3.37). 80% of people who were invited to complete questionnaires returned them. Response rates were higher among older age groups. The overall response rate to the survey was 20%, relative to the original number approached for consent (1951/10000). CONCLUSION: The requirement of a separate, prior consent stage may significantly reduce overall survey response rates and necessitate the use of substantially larger initial samples for population surveys. It may also exacerbate non-response bias with respect to demographic variables. (+info)
(2/116) Reasons physicians accepted or declined smallpox vaccine, February through April, 2003.
From February to April 2003, we performed an e-mail-based survey to assess responses of physicians at Yale University to being offered smallpox vaccine. Of 58 respondents, 3 (5%) had been or intended to be vaccinated. Reasons cited for declining vaccination included: belief that benefits did not outweigh risks (55%), belief that the vaccination program was unnecessary (18%), desire to wait and see what side effects occurred in vaccinees (11%), and worries about compensation or liability (7%). Most (94%) considered risks to themselves, family, or patients in their decision. Only 3% thought a smallpox attack in the next 5 years was likely or very likely. Physicians did not accept the smallpox vaccine because they did not believe the potential benefits were sufficient. (+info)
(3/116) An alternative trial design to overcome validity and recruitment problems in primary care research.
BACKGROUND: Although the randomized controlled trial is widely accepted as the best design to investigate new interventions, conducting a trial in primary care may present researchers with many methodological problems. OBJECTIVE: Our aim was to present an alternative trial design to overcome internal validity and recruitment problems. METHODS: In a randomized controlled trial, fatigued employees absent from work were selected among the population of an occupational health service in the South of The Netherlands. Patients randomly assigned to the experimental condition received cognitive behavioural therapy by a research GP near their home address, whereas patients in the control group received no intervention. We describe our considerations for building an alternative design. Research GPs and patients were recruited separately for the study. The pre-randomization design was applied. RESULTS: Nine research GPs performed all the interventions. Seventy-six experimental patients and 75 control patients were selected for study participation. Of these, only six patients in the experimental group and seven patients in the control group withdrew from the study at some point during follow-up. CONCLUSION: Results suggest that recruitment and randomization procedures in the alternative design served their purpose well. The alternative design proposed here might have several advantages compared with conventional trial procedures. However, our design is not widely applicable and there are ethical aspects involved that should be considered. Researchers should address their creativity when trying to minimize the problems they may encounter in designing a study. (+info)
(4/116) Should patients be allowed to veto their participation in clinical research?
Patients participating in the shared benefits of publicly funded health care enjoy the benefits of treatments tested on previous patients. Future patients similarly depend on treatments tested on present patients. Since properly designed research assumes that the treatments being studied are-so far as is known at the outset-equivalent in therapeutic value, no one is clinically disadvantaged merely by taking part in research, provided the research involves administering active treatments to all participants. This paper argues that, because no other practical or moral considerations count decisively against so doing, we could and should oblige patients to agree to receive indicated treatment within the terms of any concurrent research protocols. This ensures their treatment will benefit not only themselves but also future patients through contributing to new knowledge. By analogy with the paying of income tax, patients should not be allowed to "veto" their social responsibility to take part in clinical research. (+info)
(5/116) Attrition and bias in the MRC cognitive function and ageing study: an epidemiological investigation.
BACKGROUND: Any hypothesis in longitudinal studies may be affected by attrition and poor response rates. The MRC Cognitive Function and Ageing study (MRC CFAS) is a population based longitudinal study in five centres with identical methodology in England and Wales each recruiting approximately 2,500 individuals. This paper aims to identify potential biases in the two-year follow-up interviews. METHODS: Initial non-response: Those not in the baseline interviews were compared in terms of mortality to those who were in the baseline interviews at the time of the second wave interviews (1993-1996). Longitudinal attrition: Logistic regression analysis was used to examine baseline differences between individuals who took part in the two-year longitudinal wave compared with those who did not. RESULTS: Initial non-response: Individuals who moved away after sampling but before baseline interview were 1.8 times more likely to die by two years (95% Confidence interval(CI) 1.3-2.4) compared to respondents, after adjusting for age. The refusers had a slightly higher, but similar mortality pattern to responders (Odds ratio 1.2, 95%CI 1.1-1.4). Longitudinal attrition: Predictors for drop out due to death were being older, male, having impaired activities of daily living, poor self-perceived health, poor cognitive ability and smoking. Similarly individuals who refused were more likely to have poor cognitive ability, but had less years of full-time education and were more often living in their own home though less likely to be living alone. There was a higher refusal rate in the rural centres. Individuals who moved away or were uncontactable were more likely to be single, smokers, demented or depressed and were less likely to have moved if in warden-controlled accommodation at baseline. CONCLUSIONS: Longitudinal estimation of factors mentioned above could be biased, particularly cognitive ability and estimates of movements from own home to residential homes. However, these differences could also affect other investigations, particularly the estimates of incidence and longitudinal effects of health and psychiatric diseases, where the factors shown here to be associated with attrition are risk factors for the diseases. All longitudinal studies should investigate attrition and this may help with aspects of design and with the analysis of specific hypotheses. (+info)
(6/116) Effect of advanced provision of emergency contraception on women's contraceptive behaviour: a randomized controlled trial.
BACKGROUND: Emergency contraception (EC) can prevent pregnancy but is under-used. Advanced provision increases use but the effect on contraceptive behaviour varies. METHODS: Women aged 18-45 years, using less effective contraceptives, were randomized to either advanced provision of three courses of EC (intervention) or to obtaining each course from clinic (control). EC use and contraceptive behaviour were monitored for 1 year. RESULTS: In all, 1030 women were recruited in 6 months. The mean+/-SD number of courses of EC used in intervention versus control group was 0.56+/-1.2 versus 0.20+/-0.6 (P<0.001). In the intervention group, 47% women aged <26 years used at least one course of EC compared with 23% of older women (P<0.001). The majority of women used condoms before (intervention 89%, control 91%) and during the study (89% for both groups). Consistency of contraceptive use was higher during the study (65 versus 60% of women in both groups) (P<0.001). There were 17 unplanned pregnancies, eight in the intervention group, six of whom did not use EC in the conception cycle. CONCLUSIONS: Advanced provision increases EC use especially among young women in Hong Kong. Contraceptive choice and consistency of use remains the same even among young women. (+info)
(7/116) Alternative methods for handling attrition: an illustration using data from the Fast Track evaluation.
Using data from the evaluation of the Fast Track intervention, this article illustrates three methods for handling attrition. Multiple imputation and ignorable maximum likelihood estimation produce estimates that are similar to those based on listwise-deleted data. A panel selection model that allows for selective dropout reveals that highly aggressive boys accumulate in the treatment group over time and produces a larger estimate of treatment effect. In contrast, this model produces a smaller treatment effect for girls. The article's conclusion discusses the strengths and weaknesses of the alternative approaches and outlines ways in which researchers might improve their handling of attrition. (+info)
(8/116) Assessing response bias from missing quality of life data: the Heckman method.
BACKGROUND: The objective of this study was to demonstrate the use of the Heckman two-step method to assess and correct for bias due to missing health related quality of life (HRQL) surveys in a clinical study of acute coronary syndrome (ACS) patients. METHODS: We analyzed data from 2,733 veterans with a confirmed diagnosis of acute coronary syndromes (ACS), including either acute myocardial infarction or unstable angina. HRQL outcomes were assessed by the Short-Form 36 (SF-36) health status survey which was mailed to all patients who were alive 7 months following ACS discharge. We created multivariable models of 7-month post-ACS physical and mental health status using data only from the 1,660 survey respondents. Then, using the Heckman method, we modeled survey non-response and incorporated this into our initial models to assess and correct for potential bias. We used logistic and ordinary least squares regression to estimate the multivariable selection models. RESULTS: We found that our model of 7-month mental health status was biased due to survey non-response, while the model for physical health status was not. A history of alcohol or substance abuse was no longer significantly associated with mental health status after controlling for bias due to non-response. Furthermore, the magnitude of the parameter estimates for several of the other predictor variables in the MCS model changed after accounting for bias due to survey non-response. CONCLUSION: Recognition and correction of bias due to survey non-response changed the factors that we concluded were associated with HRQL seven months following hospital admission for ACS as well as the magnitude of some associations. We conclude that the Heckman two-step method may be a valuable tool in the assessment and correction of selection bias in clinical studies of HRQL. (+info)